Patent Abstract:
The present invention relates generally to fastening systems, and more specifically, to high tensile or high strength studs. The studs are adapted to be utilized in original manufacture or in the repair or retrofit of internal combustion engines. The improved stud technology can be utilized in the fabrication of new engine builds to improve reliability, extend product life, and the like. Likewise, the stud technology can be used to repair and/or upgrade a failed, compromised, or questionable cylinder head to engine block fastening system. Additionally, a repair or retrofit a kit can be assembled with the improved studs at its foundation. Optionally, any combination of additional items or components useful in the cylinder head to engine block fastener modification can be added to such a kit.

Full Description:
RELATED APPLICATIONS AND PRIORITY CLAIM 
       [0001]    This continuation-in-part application claims priority to provisional patent application U.S. Ser. No. 61/265,033 filed Nov. 30, 2009 and utility application U.S. Ser. No. 12/952,786 filed on Nov. 23, 2010. Each of said applications is incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to fastening systems, and more specifically, to high strength studs having dual diameters or having two opposing threaded portions, wherein each threaded portion possesses unequal major diameters. The studs are adapted to be utilized in the repair or retrofit of internal combustion engines in addition to utilization in the original manufacture of internal combustion engines. 
       BACKGROUND OF THE INVENTION 
       [0003]    Simple stud type devices as applied to internal combustion engines have certain known advantages. Nevertheless, there remain voids regarding desirable attributes pertaining to the stud fastening devices, their methods of use, as well as solving and/or overcoming the underlining problems or motive(s) that initially prompted their use. 
         [0004]    U.S. Pat. No. 5,025,556 to Stafford is one such example that discloses a method for repairing cylinder head bolt holes located in engine blocks. Stafford discloses a method where a problem cylinder head bolt hole or block hole, located in an engine block, is drilled out, followed by a measuring step to precisely determine the new hole diameter, whereby a custom made stud is created in a subsequent step to precisely fit into the newly created block-hole. The method substantially describes a procedure to create fastening hardware in on-demand, or real-time type of scenario. Such a procedure is not only complex and time consuming, but calls for the use of relatively expensive and complex equipment typically left to specially trained, skilled workers to operate (e.g. a lathe, and the like). The use of an adhesive having a cure time of 12 hours is also included in the repair process. Furthermore, Stafford clearly teaches the application and use of a fine thread (e.g. UNF) types directed to stud or fastener to block-hole interfaces. Unfortunately, fine thread types and corresponding interfaces are more susceptible to cross-threading, have a greater tendency to strip, are more time consuming to install, as well as being more prone to corrosion damage when compared to the coarse thread (e.g. UNC) counterpart. The use of fine thread fastening interfaces, particularly with the more susceptible present day engine blocks fabricated from aluminum based alloys, increase the likelihood of fastener-block interface failure. 
         [0005]    Present day cylinder head to engine block bolt type fastener repairs, as well as the teaching of aforementioned U.S. Pat. No. 5,025,556 to Stafford, include the installment of multi-interface coupling devices such as threaded sleeves, threaded plugs, threaded inserts, self-tapping threaded inserts, and the like, into the block-hole. Such multi-interface coupling devices prepare the engine block for receiving the corresponding stud or bolt fastener. The installation of such multi-interface coupling devices can be cumbersome due to the absence of ordinary tool interface features, thereby requiring the use of specialty tools. Furthermore, often such multi-interface coupling devices are prone to premature failure. Such premature failures can be attributed a multitude of causes, including: inherent material weakness involving one or more fastening interface sites, thermal cycling fatigue, coupling device dimensional inadequacies, installation errors, and the like. Additionally, multi-interface coupling devices often exhibit diameter expansion when torque is applied, the strain created has the potential to crack engine blocks as well as strip the sleeve&#39;s internal threads. 
         [0006]    Overall, a need still exists for a cylinder head to engine block fastening device that is reliable, possesses a long service life, and lends itself to uncomplicated, quick installation. Applications for such an improved fastening device or devices would include: new engine fabrication, retrofitting used engines in need of repair, upgrades, or the like. 
         [0007]    The purpose of the present invention is to overcome the long felt need associated with the multitude of shortcomings in the present and aforementioned prior art. Additionally, the present invention includes the introduction of additional novel features giving rise to further advancements resulting in an improved fastening device. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention relates to high tensile or high strength studs that are adapted to be utilized in the original manufacture or in the repair and/or retrofit of cylinder head-engine block fastener interfaces commonly associated with internal combustion engines. The improved stud device and embodiments provides numerous advantages, which include: increased engine robustness and reliability associated with cylinder head-engine block interface portion of internal combustion engines. Additionally, an installation, repair or retrofit kit is the topic of an alternate embodiment that includes the appropriate number of improved studs for a given application. More comprehensive kits allow the introduction of any combination of additional items or components useful in the attachment of a cylinder head to engine block, so to streamline the fastening process. 
         [0009]    It is understood that the use of the improved stud technology directed to the cylinder head-engine block application is considered one of many exemplary applications; other engine block based issues can be solved by use of this fastening technology. For example, the repair of oil filter mounts where the engine block bolt holes associated with the oil filter become stripped or damaged and require repair; such occurrences can occur quite easily with aluminum block engine types. 
         [0010]    It is an object of the present invention to provide a pre-manufactured improved stud fastener or fasteners, adapted for a specific engine make, model, type, or style, for reliably securing a cylinder head to an engine block that ensures relatively simple and trouble-free installation on new engine builds as well as on pre-existing or used engines requiring repair, retrofitting, or the like. The availability of the pre-manufactured improved stud fasteners includes: individual units, a complete set given a specific engine, or in a kit type format that further comprises useful installation components. 
         [0011]    It is another object of the present invention to provide an improved stud fastener where each end is optimized to corresponding interfaces as well as adapted to the specific engine geometry of interest, e.g. an engine block threaded hole, cylinder head nuts, cylinder head apertures, internal cylinder head fastener pathway, and the like. 
         [0012]    It is yet another object of the present invention to provide an improved stud fastener with features that help compensate for the less desirable material properties associated with aluminum or aluminum alloy engine blocks. Such features include the use of enlarged engine block threaded holes, the use of coarse thread (e.g. UNC standard) on engine block-stud interfaces that possess increased thread depths resulting in improved reliability, strength, and the like. 
         [0013]    It is an object of the present invention to provide a pre-manufactured improved stud fastener that includes an integrated cylindrical locating or alignment feature to quickly and accurately position cylinder heads onto the engine block. The original alignment feature provided with an engine block is typically a press-fit bushing disposed in the corner located engine block holes dedicated to cylinder head fastening. The improved stud fastener possessing the integrated cylindrical alignment feature will replace the press-fit bushing feature since the press-fit bushings are typically removed when performing a cylinder head to engine block repair or retrofit. 
         [0014]    It is another object of the present invention to provide an improved stud fastener where the first end or the cylinder head end of the stud possesses at least two flat portions to aid in installation. The features are preferably located on the tip of portion of the cylinder head end side of the stud fastener. Since machining flats, and the like, can alter the mechanical strength of a component, the installation feature is preferably disposed on a non-critical or non-stressed portion of the improved stud fastener (e.g. cylinder end side or first end) when the device is functionally installed. Such a prehensile feature will provide a user with the option to use a fastening tool such as an adjustable wrench, or the like, to assist in the stud installation. 
         [0015]    It is yet another object of the present invention to provide a plurality of improved stud fasteners in a kit type format including additional components that are required or useful in the installation process. Additional components include: engine block aligning plate, instructions, a tap, drill bit, nuts, washers, and the like. 
         [0016]    It is an object of the present invention to provide a one-piece repair scheme using the improved stud fastener, as opposed to using a dual interface coupling device (e.g. threaded sleeve) and an original style bolt. By employing the one-piece repair operation, the user eliminates the risk of cracking the engine block, and thread stripping associated with threaded sleeve diameter expansion during the torquing process. Additionally, the improved stud fasteners, due to their elongated geometry, can often be installed into an engine block by hand, thereby streamlining the installation process. 
         [0017]    The aforementioned objects are not intended to be exhaustive; other obvious objects of the present invention will be portrayed in the disclosure hereinafter. Whereas there may be many embodiments of the present invention, each embodiment may meet one or more of the foregoing recited objects in any combination. It is not intended that each embodiment will necessarily meet each objective. 
         [0018]    Thus, having broadly outlined the more important features of the present invention in order that the detailed description thereof may be better understood, and that the present contribution to the art may be better appreciated, there are, of course, additional features of the present invention that will be described herein and will form a part of the subject matter of the claim(s) appended to this specification. 
         [0019]    In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The present invention is capable of other embodiments and of being practiced and carried out in various ways 
         [0020]    As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the description be regarded as including such equivalent construction insofar as they do not depart from the spirit and scope of the conception regarded as the present invention. 
       PARTICULAR ADVANTAGES OF THE INVENTION 
       [0021]    The improved stud technology can be utilized in the fabrication of new engine builds to improve reliability, extend product life, and the like. Likewise, the stud technology can be used to repair or upgrade a cylinder head to engine block fastening system. 
         [0022]    Additionally, an installation, repair or retrofit kit containing the improved studs provides a convenient means for organizing the desired components for a specific make and model vehicle. It is understood that a variety of stud kits can be assembled having any combination of additional items or components useful in the cylinder head to engine block fastener improved stud installation process. 
         [0023]    Furthermore, the larger diameter and deeper thread when utilized in the stud-engine block interface is of particular value when working with the increasingly popular, modern aluminum alloy engine blocks. This is due, in part, to the aluminum alloys (e.g. A356, 242, 319) used in engine block fabrication, being inherently weaker and more susceptible to damage and corrosion than the heavier, cast iron and other ferrous alloy based engine blocks. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The invention will be described by reference to the specification and the drawings, in which like numerals refer to like elements, and wherein: 
           [0025]      FIG. 1  illustrates a top perspective view of an exemplary unmodified engine block in accordance with a typical engine block design. 
           [0026]      FIG. 1   a  illustrates a sectional side view of a tapped hole with alignment bushing contained within an unmodified engine block in accordance with a typical engine block design. 
           [0027]      FIG. 1   b  illustrates a sectional side view of a tapped hole contained within an unmodified engine block in accordance with a typical engine block design. 
           [0028]      FIG. 2  illustrates a top perspective view of an exemplary modified engine block in accordance with one embodiment of the present invention. 
           [0029]      FIG. 2   a  illustrates a sectional side view of a tapped hole with alignment bushing receiving feature contained within a modified engine block in accordance with one embodiment of the present invention. 
           [0030]      FIG. 2   b  illustrates a sectional side view of a tapped hole contained within a modified engine block in accordance with one embodiment of the present invention. 
           [0031]      FIG. 3  illustrates a top perspective view of an exemplary improved stud fastener system in accordance with one embodiment of the present invention. 
           [0032]      FIG. 3   a  illustrates a sectional front view of an exemplary improved stud fastener system in accordance with the embodiment depicted in  FIG. 3 . 
           [0033]      FIG. 3   b  illustrates a sectional front view of an exemplary improved stud fastener having a non-continuous threaded section in accordance with one embodiment of the present invention. 
           [0034]      FIG. 4  illustrates a top perspective view of an exemplary improved stud fastener having an integrated cylinder head aligning feature in accordance with one embodiment of the present invention. 
           [0035]      FIG. 4   a  illustrates a sectional front view of an exemplary improved stud fastener having an integrated cylinder head aligning feature in accordance with the embodiment depicted in  FIG. 4 . 
           [0036]      FIG. 4   b  illustrates a sectional front view of an exemplary improved stud fastener having an integrated cylinder head aligning feature and a non-continuous threaded section in accordance with one embodiment of the present invention. 
           [0037]      FIG. 5  illustrates details and defining aspects of a typical threaded fastener/fastening interface. 
           [0038]      FIG. 6  illustrates a sectional front view of an exemplary multifunctional plate, combination aligning plate, combo jig, or combo plate. 
           [0039]      FIG. 6   a  illustrates a perspective view of an exemplary combination aligning plate and components directly associated with use of the alignment plate. 
           [0040]      FIG. 6   b  illustrates a perspective view of exemplary combination aligning plate use/utility and components directly associated with use of the alignment plate as directed to an engine block face. 
           [0041]      FIG. 6   c  illustrates a sectional front view of the combination aligning plate of  FIG. 6  with exemplary dimensional details. 
           [0042]      FIG. 6   d  illustrates a sectional side view of the combination aligning plate of  FIG. 6  with exemplary dimensional details. 
           [0043]      FIG. 7  illustrates a retrofitted engine surrounded by typical exemplary components that can comprise a cylinder head to engine block fastener installation or retrofit kit. 
           [0044]      FIG. 8  illustrates a top perspective exploded view of retrofitted engine showing cylinder head, or engine cover and associated fastening components. 
           [0045]      FIG. 8   a  illustrates a sectional front view of a stud fastener mounted in an engine block modified tapped hole. 
           [0046]      FIG. 8   b  illustrates a sectional front view of a stud-alignment fastener mounted in an engine block modified tapped-alignment hole. 
           [0047]      FIG. 8   c  illustrates a sectional front view of a stud fastener with tool interface mounted in an engine block modified tapped hole. 
           [0048]      FIG. 8   d  illustrates a sectional front view of stud-alignment fastener with a tool interface mounted in an engine block modified tapped-alignment hole. 
       
    
    
       [0049]    The drawings are not to scale, in fact, some aspects have been emphasized for a better illustration and understanding of the written description. 
         [0050]    In order to help facilitate the understanding of this disclosure, a parts/features list numbering convention has been employed. The first digit in three digit part numbers refers to the Figure number and/or Figure number family where the part was first introduced, or is best depicted. Likewise, in four digit part numbers, the first two digits refer to the Figure number where the part was first introduced, or is best depicted. Although this disclosure may at times deviate from this convention, it is the intention of this numbering convention to assist in an expeditious comprehension of the present invention. 
       PARTS/FEATURES LIST 
       [0000]    
       
           100 . unmodified engine block 
           102 ,  110 : tapped hole with alignment bushing 
           104 ,  106 ,  108 ,  112 ,  114 ,  116 ,  118 ,  120 : tapped hole 
           130 . tapped hole with alignment bushing (sectional view) 
           132 . alignment pin or alignment bushing 
           134 . alignment bushing contact height 
           136 . unmodified internal thread 
           136   a . unthreaded portion of tapped hole 
           138 . functional depth of unmodified hole 
           138   a . thread length 
           140 . tapped hole size or diameter 
           150 . sectional view of tapped hole 
           156 . unmodified internal thread 
           158 . functional depth of unmodified hole 
           160 . tapped hole size or diameter 
           200 . modified engine block 
           202 ,  210 : tapped-alignment hole 
           204 ,  206 ,  208 ,  212 ,  214 ,  216 ,  218 ,  220 : modified tapped hole 
           230 . modified tapped-alignment hole (sectional view) 
           232 . unthreaded internal area 
           236 . modified internal thread 
           238 . functional depth of modified hole 
           238   a . thread length 
           238   b . unthreaded internal area depth 
           240 . modified tapped hole size 
           250 . modified tapped hole sectional view 
           256 . modified internal thread 
           258 . functional depth of modified hole 
           260 . modified tapped hole size 
           300 . stud fastener 
           302 . first end or cylinder head end 
           304 . midsection 
           306 . second end or engine block end 
           312 . second threaded feature 
           314 . second threaded feature length 
           314   a . second diameter or second end diameter 
           316 . midsection diameter 
           318 . first threaded feature length 
           318   a . first diameter or first end diameter 
           320 . first threaded feature 
           322 . overall length (stud fastener) 
           330 . stud fastener with tool interface 
           332 . first end, (stud fastener with tool interface) 
           332   a . first flat feature 
           332   b . second flat feature 
           334 . non-continuous threaded section 
           336 . first and second flat feature length 
           338 . distance from first to second flat feature 
           400 . stud-alignment fastener 
           402 . first end or cylinder head end 
           404 . midsection 
           406 . second end or engine block end 
           406   a . second end threaded portion 
           406   b . second end non-threaded portion or alignment feature (for cylinder head) 
           406   c . non-threaded second diameter 
           412 . second end threaded feature 
           412   a . threaded second diameter 
           414 . second end length 
           414   a . threaded portion length (second end) 
           414   b . non-threaded portion length (second end) 
           416 . midsection diameter 
           418 . first threaded feature length 
           418   a . first diameter 
           420 . first threaded feature 
           422 . stud-alignment fastener overall length 
           430 . stud-alignment fastener with tool interface 
           432 . first end 
           432   a . first flat feature 
           432   b . second flat feature 
           434 . non-continuous threaded section 
           436 . first and second flat feature length 
           438 . distance from first to second flat feature 
           500 . definitional detail of a threaded fastening/fastener interface 
           501   a . tapped hole 
           501   b . bolt, screw, stud, or the like 
           502 . major diameter, Dmaj, (of bolt) 
           504 . effective pitch diameter, Dp, (of bolt) 
           506 . minor diameter, Dmin, (of bolt) 
           508 . thread height, H 
           510 . 5 H/8, actual thread depth 
           512 . H/4 
           514 . H/8 
           516 . 3 H/8 
           600 . combination aligning plate, combo jig, or combo plate 
           602   a . mounting hole 
           602   b . mounting hole 
           604 . drill bit alignment hole 
           606 . tap alignment hole 
           608   a . modified tapped hole bolt 
           608   b . modified tapped hole bolt 
           610   a . unmodified tapped hole bolt 
           610   b . unmodified tapped hole bolt 
           612 . drill bit assembly 
           612   a . drill bit 
           612   b . drill bit collar 
           614 . tap 
           616 . front face 
           618 . back face 
           620 . engine block face 
           622   a  through  622   j , engine block tapped holes/untapped holes 
           630 . combination aligning plate width 
           632 . combination aligning plate height 
           634 . distance between mounting hole  602   b  and tap alignment hole  606   
           636 . distance between mounting hole  602   a  and tap alignment hole  606   
           638 . distance between mounting hole  602   b  center and right plate edge 
           640 . combination aligning plate thickness 
           642 . height of mounting hole  602   b  feature 
           644 . tap alignment hole  606  feature diameter 
           646 . tap alignment hole  606  feature end to end height 
           700 . retrofitted engine 
           702 . kit instructions 
           704 . cylinder head washers 
           706 . cylinder head nuts 
           708 . combination aligning plate assemblage 
           710 . thread locker 
           800 . exploded view of retrofitted engine 
           802 . cylinder head or engine cover 
           804 . height of stud  300  above surface of engine block  200   
           806 . height of stud  400  above surface of engine block  200   
           808 . height of stud  330  above surface of engine block  200   
           810 . height of stud  430  above surface of engine block  200   
           812 . stud  400  alignment feature height above engine block  200  surface 
           814 . stud  430  alignment feature height above engine block  200  surface 
       
     
       DEFINITIONS OF TERMS USED IN THIS SPECIFICATION 
       [0174]    The improved stud fasteners and stud fasteners components for reliably fastening a cylinder head to an engine block, associated kits, in addition to the various embodiments disclosed, shall have equivalent nomenclature, including: the stud technology, the improved stud, the device, the embodiment, the present invention, or the invention. Additionally, the term “exemplary” shall possess only one meaning in this disclosure; wherein the term “exemplary” shall mean: serving as an example, instance, or illustration. 
         [0175]    The discussions in this disclosure refer to the right-handed threading system due to the standard or convention in the art. It is understood that functionally, a left-handed threading system would provide equivalent performance, and therefore it is the intention of the present invention to embrace both convention systems. 
         [0176]    The term cylinder head failure shall include any failures caused by the loss of specified fastening torque (required tensile fastening stress) pertaining to any of the cylinder head to engine block fasteners e.g. gasket failure, pressure loss, and the like. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0177]    The discussion hereafter will primarily focus on an eight cylinder, ninety degree V-block based engine for exemplary purposes only. The intention is to include an exemplary discussion to assist in the understanding of the present invention and not to limit the present invention to any specific engine geometry, or to any single set of dimensional values as it pertains to the present invention. It is understood that the present invention has utility with a multitude of existing engine makes and models, and is expected to cooperate with future engine designs as well. Furthermore, the discussion will closely examine one face of the V-block engine geometry with the understanding that all discussions equally apply to the substantially identical, mirror image, opposing side. 
         [0178]    An exemplary engine system, where one embodiment of the present invention is adapted to, is depicted in  FIGS. 1 ,  1   a , and  1   b . The figures show various views and aspects of an exemplary unmodified engine block system, more specifically an eight cylinder, Northstar engine, commonly found in certain Cadillac models as well as other automobile types. 
         [0179]    Referring to  FIG. 1 , depicted is unmodified engine block  100  having two tapped holes with alignment bushings  102 ,  110 , and eight tapped holes  104 ,  106 ,  108 ,  112 ,  114 ,  116 ,  118 ,  120 , located on each side of the engine block  100 . The tapped holes with alignment bushings  102 ,  110 , are designed to snugly mate with corresponding mating-alignment features located on cylinder head  802  in addition to enabling fastening; this arraignment is best illustrated in  FIG. 8 . Such cylinder head alignment designs are commonly used in the engine manufacturing industry. The primary function of the aforementioned eight tapped holes ( 104 ,  106 ,  108 ,  112 ,  114 ,  116 ,  118 , and  120 ) is to fasten cylinder head  802  to unmodified engine block  100  once alignment has been achieved via alignment bushings  132  depicted in  FIG. 1   a.    
         [0180]    Referring to  FIG. 1   a , depicted is a sectional view of a tapped hole with alignment bushing  130 ; this figure provides details regarding tapped holes with alignment bushings  102 ,  110  depicted in  FIG. 1 . Tapped hole  130  possesses tapped hole size or diameter  140 , and internal thread  136 . The exemplary Northstar engine possesses an M11×1.5 dimension for internal thread  136 . 
         [0181]    The alignment pin, or alignment bushing  132  is a metallic component that is typically press-fit into the unthreaded portion of tapped hole  136   a  region of tapped holes  102 ,  110  depicted in  FIG. 1 . Protruding portion of alignment bushing  132  having an alignment bushing contact height  134 , creates a protuberance that provides an aligning function between cylinder head  802  depicted in  FIG. 8  and unmodified engine block  100  depicted in  FIG. 1  when joined. Tapped hole with alignment bushing  130  possesses functional depth  138  wherein a portion is threaded as depicted by thread length  138   a.    
         [0182]    Referring to  FIG. 1   b , depicted is a sectional view of tapped hole  150 ; this figure is similar to the aforementioned tapped hole with alignment bushing  130  without the alignment bushing feature, i.e. alignment bushing  132 . Sectional view  150  provides details regarding each of eight tapped holes  104 ,  106 ,  108 ,  112 ,  114 ,  116 ,  118 ,  120 , located on one face of the engine block  100  depicted in  FIG. 1 . Sectional view  150  depicts a tapped hole having a tapped hole size or diameter  160 , wherein the exemplary Northstar engine possesses an M11×1.5 type thread for unmodified internal thread  156 . Sectional view additionally depicts functional depth of unmodified hole  158  where substantially the entire depth is threaded with unmodified internal thread  156 . 
         [0183]      FIGS. 1   a  and  1   b , in the present example, both possess the same M11×1.5 type thread for depicting unmodified internal thread  136 , and unmodified internal thread  156 , respectively. At this point, the basic properties of these closely related threaded holes, whose function is to couple with M11×1.5 type bolts, will be reviewed. An ISO-Metric, M11×1.5 type thread possesses a nominal diameter of 11 mm (0.4331 inch) and a pitch (P) of 1.5 mm (0.0591 inch). For the ISO-Metric thread form, as well as the UNF and UNC thread forms, the actual thread depth (d) is determined by the relationship given by: d=0.541266×P. Therefore, the actual thread depth (d) for an M11×1.5 type thread is 0.8119 mm (0.0320 inches). These particular fastener attributes have been linked, at least in part, to cylinder head  802  failure on the General Motors Northstar engine depicted as engine block  100  depicted in  FIG. 1 . One of the primary enablers for such a failure, in combination with said fastener attributes, is engine block  100  being fabricated from a light weight aluminum alloy. 
         [0184]    The following table is included to summarize the thread depth advantage associated with exemplary thread type upgrades. 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
               
               
                   
                   
                   
                 % increase in 
               
               
                   
                 Starting Thread 
                 Modified Thread 
                 Thread depth (d) 
               
               
                   
               
             
             
               
                 Thread Type 
                 M11 × 1.5 
                 5/8 × 11 UNC 
                 53.8% 
               
               
                 (Thread depth d) 
                 (0.0320 inches) 
                 (0.0492 inches) 
                   
               
               
                 Thread Type 
                 7/16 × 20 UNF 
                 5/8 × 11 UNC 
                 81.8% 
               
               
                 (Thread depth d) 
                 (0.0271 inches) 
                 (0.0492 inches) 
               
               
                   
               
             
          
         
       
     
         [0185]    The original ISO-Metric, M11×1.5 type bolts (not shown) installed in the Northstar engine, depicted as engine block  100 , have been known to break free from representative block  100 , thereby causing cylinder head  802  failure, sealing issues and the like. Examination of the failed original ISO-Metric, M11×1.5 type bolts and unmodified internal threads  136  and  156  has revealed that the failure is primarily due to aluminum thread deterioration associated with engine block  100 . Although the failure mode is not fully understood, reasonable explanations have been suggested. 
         [0186]    NASA Reference Publication 1228 entitled “Fastener Design manual” authored by Richard T. Barrett of the Lewis Research Center of Cleveland, Ohio offers plausible explanations. An excerpt from page 5 teaches the following: 
       Galvanic Corrosion: 
       [0187]    Galvanic corrosion is set up when two dissimilar metals are in the presence of an electrolyte, such as moisture. A galvanic cell is created and the most active (anode) of the two materials is eroded and deposited on the least active (cathode). Note that the farther apart two materials are in the following list, the greater the galvanic action between them. 
         [0188]    According to reference 2 the galvanic ranking of some common engineering materials are as follows: 
         [0189]    (1) Magnesium (most active) 
         [0190]    (2) Magnesium alloys 
         [0191]    (3) Zinc 
         [0192]    (4) Aluminum 5056 
         [0193]    (5) Aluminum 5052 
         [0194]    (6) Aluminum 1100 
         [0195]    (7) Cadmium 
         [0196]    (8) Aluminum 2024 
         [0197]    (9) Aluminum 7075 
         [0198]    (10) Mild steel 
         [0199]    (11) Cast iron 
         [0200]    (35) Graphite 
         [0201]    (36) Gold (least active) 
       Stress Corrosion: 
       [0202]    Stress corrosion occurs when a tensile-stressed part is placed in a corrosive environment. An otherwise ductile part will fail at a stress much lower than its yield strength because of surface imperfections (usually pits or cracks) created by the corrosive environment. In general, the higher the heat-treating temperature of the material (and the lower the ductility), the more susceptible it is to stress corrosion cracking. 
         [0203]    A significant amount of aluminum metal and corrosion byproducts have been detected on the threads of Northstar original ISO-Metric, M11×1.5 type bolts that have experienced cylinder head  802 , depicted in  FIG. 8 , related type failures. According to Barrett&#39;s disclosure, this observation supports the suggestion of galvanic corrosion, since it is expected that the anode (aluminum block in this case) will deposit on the cathode (the iron based M11×1.5 type bolts). It is understood that this type of corrosion proceeds in a progressive manner. The corrosion is initiated at the dissimilar metal interface, and as the aluminum threads deteriorate from the thinner thread edge inward, the load remaining on the remaining thread material increases until a shear failure of the aluminum material occurs. The relatively high operating temperatures of automobile engines (195 to 276 deg.), as well as the associated thermal cycling create an additional stressor that exacerbates the situation. Taking an alternative point of view, as the corrosion progresses, the bolt pullout force from engine block  100  progressively decreases until shear failure occurs at the point where the remaining aluminum metal contained in the diminishing threads can no longer support the applied load. Pullout force (P) associated with a tapped hole is determined by the relationship (also provided by the aforementioned NASA Reference Publication 1228) is given by the following equation: 
         [0000]    
       
         
           
             P 
             = 
             
               
                 π 
                  
                 
                     
                 
                  
                 d 
                  
                 
                     
                 
                  
                 m 
                  
                 
                     
                 
                  
                 Fs 
                  
                 
                     
                 
                  
                 L 
               
               3 
             
           
         
       
     
       Where 
       [0204]    P Pullout force, lbs 
         [0205]    dm mean diameter of threaded hole, in 
         [0206]    Fs material ultimate or yield shear stress 
         [0207]    L length of thread engagement, in 
         [0208]    ⅓ the factor introduces an additional margin of safety term to allow for mismatched threads, in a perfectly mated situation the factor would be ½ 
         [0209]    An analysis of the aforementioned relationships reveals that the reliability of the fastening system associated with cylinder head  802  to engine block  100  can be increased; cylinder head  802  failures are pushed out in time or eliminated by the implementation of various fixes or methods including: 
         [0210]    1. Increasing the diameter, major diameter, or dm (diameter) defined in the previous equation of tapped hole size  140  and  160  of  FIGS. 1   a  and  1   b  respectively. Such a modification will increase the thread engagement (surface area) of the fastening interface, thereby considerably lengthening the time to shear, pull-out, or letting-go type of failures by initially starting out with a larger pullout force (P) value. An alternative perspective teaches that the induced tensile load is shared by a larger fastening interface. 
         [0211]    2. Increasing the thread depth, actual thread depth (d), or the like. The fastener-hole illustration of  FIG. 5  depicts an exemplary thread depth attribute given by thread height (H)  508 . Such an alteration will not only increase the fastener thread engagement, but also increase thread penetration into the tapped hole fastening interface. A longer thread height, given a set corrosion rate that is directional in nature (outer surface to inner bulk), will lengthen the time required to reach fastening interface failure. This is primarily due to the larger volume of fastening material that must go through the corroding process combined with the longer corrosion travel path. 
         [0212]    3. Utilizing an electrically insulating finish on the surface of the fastener, the tapped hole, or any combination thereof to isolate the dissimilar metals to prevent or reduce the onset of galvanic corrosion. There are numerous methods and materials to create insulative coatings or thin films to accomplish such a task. For example, aluminum anodizing, the use of primers, oxides, and ceramic coatings (e.g. titanium nitride), as well as the use of certain thread locking materials that possess adhesive type properties as well as insulating properties can also provide a benefit. Additionally, durable dry film lubricants such as EMRALON 330 (available through Acheson-Henkel Company of 32100 Stephenson Highway, Madison Heights, Mich. 48071, and the like, can be used to provide the electrical insulation as well as provide a dry, clean, permanently lubricated surface to assist in installation and subsequent engine overhauls where disassembly may be required. 
         [0213]    Referring to  FIG. 2 , depicted is modified engine block  200 . Modified engine block  200  is an upgraded version of unmodified engine block  100  upgraded to accept improved stud fasteners  300  and stud-alignment fasteners  400  depicted in  FIG. 3  and  FIG. 4  respectively. The basic process or steps required for engine block hole modifications are known in the art. Alternatively,  FIG. 6   b  illustrates a perspective view of an exemplary combination aligning plate along with supporting components comprising an installation kit; the illustration depicts component use/utility directed to engine block face  620 , depicted in  FIG. 6   b , modification leading to improved stud fastener adaptation and installation. 
         [0214]    Modified engine block  200  possesses two tapped-alignment holes  202 ,  210 , and eight modified tapped holes  204 ,  206 ,  208 ,  212 ,  214 ,  216 ,  218 ,  220 . All of the aforementioned hole counterparts are also present on the opposing side or mirror-image cylinder face of modified engine block  200  of  FIG. 2 . 
         [0215]    Tapped-alignment holes  202 ,  210 , are designed to accept stud-alignment fasteners  400  depicted in  FIG. 4 , having a cylinder head-alignment feature  406   b  configured to occupy a portion of unthreaded internal area  232  shown in  FIG. 2   a . When the fastener is installed, cylinder head-alignment feature  406   b  provides a cylindrical projection, thereby providing a similar function once provided by alignment bushing  132  depicted in  FIG. 1   a . When installing cylinder head  802  of  FIG. 8  or the like, the cylinder head-alignment feature  406   b  first mates with corresponding mating-alignment features located on cylinder head  802  to ensure proper alignment. The inclusion or integration of such an alignment feature into a stud fastener is novel and included in the present invention. 
         [0216]    The aforementioned eight modified tapped holes  204 ,  206 ,  208 ,  212 ,  214 ,  216 ,  218 ,  220  are designed to accept stud fastener  300  of  FIG. 3 , whose function is to provide a reliable means for fastening cylinder head  802  to modified engine block  200 . Fastening cylinder head  802  to modified engine block  200  final affixing via cylinder head washers  704  and cylinder head nuts  706  can commence once alignment has been achieved via installed stud-alignment fasteners  400  possessing cylinder head-alignment feature  406   b . The aforementioned components, arranged in proper spatial alignment, are best depicted in  FIG. 8 . 
         [0217]      FIG. 2   a  illustrates modified tapped-alignment hole sectional view  230 , more specifically, the details pertaining to tapped-alignment holes  202 ,  210 . Modified tapped-alignment hole  230  possesses a functional depth  238  wherein a portion is threaded as depicted by thread length  238   a . Tapped-alignment hole  230  possess a modified tapped hole size  240 , wherein the modified internal thread  236  has been upgraded from the original Northstar M11×1.5 type thread to a larger, more beneficial, ⅝×11 UNC thread type that possesses a larger diameter and coarser thread, that is, fewer threads per unit length coinciding with a larger or deeper thread depth. Increases in diameter, thread depth, or any combination thereof, are aforementioned features providing life extension benefits. 
         [0218]    Referring to  FIG. 2   b , depicted is a sectional view of modified tapped hole  250 ; this figure is similar to the aforementioned modified tapped-alignment hole  230  without the alignment feature provided by unthreaded internal area  232 . This Figure provides details pertaining to each of the eight tapped holes  204 ,  206 ,  208 ,  212 ,  214 ,  216 ,  218 ,  220 , depicted on visible face or side of the engine block  200 . Modified tapped hole  250  possess a modified tapped hole size  260 , wherein the present embodiment is a ⅝×11 UNC thread type, converted from the original Northstar engine&#39;s M11×1.5 type thread. Sectional view of modified tapped hole  250  depicts functional depth of modified hole  258  where substantially the entire hole depth is threaded with modified internal thread  256 . 
         [0219]      FIG. 3  depicts a perspective view of stud fastener  300 . The fastener in preferred embodiments is constructed, or machined from a single piece of metallic material having a generally rod like geometry. The finished stud fastener  300  possesses a first end, or cylinder head end  302  having a first diameter  318   a , a second end, or engine block end  306  possessing a second diameter  314   a.    
         [0220]    Additionally, stud fastener  300  contains a midsection  304 , having a midsection diameter  316 . Midsection  304  connects first end  302  to second end  306 . 
         [0221]    Referring to  FIG. 3   a , depicted is a front view of stud fastener  300  having overall length  322 . First end  302  has a first threaded feature  320  having a threaded feature length  318 , and a second end  306  having a second threaded feature  312  having threaded feature length  314 . Exemplary dimensions configured for use with a General Motors Northstar engine include: second threaded feature  312 , having a preferred thread type of ⅝×11 UNC; second threaded feature length  314 , having a preferred dimension of 2.0 inches; second diameter  314   a , having a preferred dimension of ⅝ inches; midsection diameter  316  having a preferred dimension of 0.43 inches; first threaded feature length  318 , having a preferred dimension of 1.50 inches; first diameter  318   a , having a preferred dimension of 7/16 inches; first threaded feature  320 , having a preferred thread type of 7/16×20 UNF; overall length  322 , having a preferred dimension of 6.13 inches. 
         [0222]      FIG. 3   b  depicts a front view of stud fastener with tool interface  330  having a non-continuous threaded section  334  located at the extreme end or distal portion of first end  332 . The non-continuous threaded section  334  is comprised of a first flat feature  332   a  having a length  336 . Preferably in a parallel plane, a distance  338  from first flat feature  332   a , resides opposing second flat feature  332   b  having a length  336 . Exemplary dimensions configured for use with a General Motors Northstar engine include: first and second flat feature length, having a preferred dimension of 0.38 inches; second threaded feature length  314 , having a preferred dimension of 2.0 inches; distance from first to second flat feature  338 , having a preferred dimension of 0.25 inches. 
         [0223]    Embodiments possessing a non-continuous threaded section  334 , or like features, enables the use of common tools, such as a wrench, to aid in the screw-in installation of stud fastener  330  into modified engine block  200 . Installation tools function by simultaneously engaging first flat feature  332   a  and opposing second flat feature  332   b  thereby capturing non-continuous threaded section  334  of stud fastener  330 . Flat features  332   a ,  332   b  are disposed at the extreme or distal end of first end  332  so to not compromise the strength of the installed stud. Non-continuous threaded section  334  is disposed on a portion of the fastening device that does not experience the fastening, or torque-down stresses associated with securing cylinder head  802  to modified engine block  200 . In preferred embodiments, final seating of the cylinder head nuts  706  avoids the potentially strength compromised non-continuous threaded section  334 ; This results in the cylinder head nuts  706  residing completely on continuously threaded section in the final state of installation. 
         [0224]    The various portions of stud  300  as shown in  FIGS. 3 ,  3   a ,  3   b , can be fabricated using a range of dimension values that will adequately function in the General Motors Northstar engine application as well as other like engine types. The following table (Table 1) delineates approximate dimension ranges (in inches) that enable the design and construction of several functional embodiments of stud  300 . 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Midsection  
                 First Threaded 
                 Second Threaded 
               
               
                 Overall Length 
                 Diameter 
                 Feature Length 
                 Feature Length 
               
               
                 (Feature 322) 
                 (Feature 316) 
                 (Feature 318) 
                 (Feature 314) 
               
               
                   
               
             
             
               
                 4.0 to 11.0 
                 0.38 to 0.60 
                 0.5 to 10.4 
                 0.5 to 3.8 
               
               
                   
               
             
          
         
       
     
         [0225]    Stud  300  approximate functional dimension ranges, wherein all values are in inches. 
         [0226]      FIG. 4 , depicts a perspective view of stud-alignment fastener  400 . The fastener in preferred embodiments is constructed, or machined from a single piece of metallic material. The stud-alignment fastener  400  possesses a first end, or cylinder head end  402  possessing a first diameter  418   a , a second end, or engine block end  406  having a length  414  possessing a threaded portion  406   a  having a threaded second diameter  412   a  and a non-threaded portion  406   b  having a non-threaded diameter  406   c . Additionally, stud-alignment fastener  400  has a midsection  404 , possessing a midsection diameter  416 . Midsection  404  connects first end  402  to second end  406 . 
         [0227]      FIG. 4   a , depicted is a front view of stud-alignment fastener  400  having overall length  422 . First end  402  has a first threaded feature  420  having a length  418 , and a second end  406  having a threaded portion  406   a  with threaded portion length  414   a  and non-threaded portion  406   b  with a non-threaded portion length  414   b.    
         [0228]    Exemplary dimensions configured for use with a General Motors Northstar engine include: non-threaded second diameter  406   c , having a preferred dimension of 0.62 inches; second threaded feature  412 , having a preferred thread type of ⅝×11 UNC; second end length  414 , having a preferred dimension of 2.38 inches; threaded portion length (second end)  414   a , having a preferred dimension of 1.56 inches; threaded second diameter  412   a , having a preferred dimension of ⅝ inches; midsection diameter  416 , having a preferred dimension of 0.43 inches; first threaded feature length  418 , having a preferred dimension of 1.50 inches; first diameter  418   a , having a preferred dimension of 7/16 inches; first threaded feature  420 , having a preferred thread type of 7/16×20 UNF; stud-alignment fastener overall length  422 , having a preferred dimension of 6.13 inches. 
         [0229]      FIG. 4   b  illustrates a front view of stud fastener with tool interface  430 , depicting a first end  432  possessing a first flat feature  432   a  at one end, and an opposing second flat feature  432   b  thereby forming a non-continuous threaded section  434 . This embodiment enables the use of common tools, for example a wrench, or the like, to engage with first flat feature  432   a  and opposing second flat feature  432   b  thereby assisting a user in the installation of stud fastener with tool interface  430  into tapped-alignment holes  202  and  210  of modified engine block  200 . Flat features  432   a ,  432   b  are disposed at the extreme or distal end of first end  432  so to not create an area of compromised strength once the device is fully installed. Non-continuous threaded section  434 , in a preferred installation embodiment, is located outside the portion of stud  130  that experiences the fastening stresses associated with securing cylinder head  802  to modified engine block  200 . The potentially strength compromised non-continuous threaded section  434  is bypassed, or avoided by cylinder head nuts  706  in the final state of installation. Exemplary dimensions configured for use with a General Motors Northstar engine include: first and second flat feature length  436 , having a preferred dimension of 0.38 inches; distance from first to second flat feature  438 , having a preferred dimension of 0.25 inches. 
         [0230]    The immediate section is directed to the topic of material selection discussion regarding stud fastener  300  and stud-alignment fastener  400 . Both stud fastener  300  and stud-alignment fastener  400  are preferably fabricated from a metal or metal alloy that is capable of withstanding the stresses associated with the specified predetermined fastener torque for a given engine application given the range of engine operating temperatures. Examples of metallic materials include selections from the family of stainless steel, chrome-moly, Inconel, titanium, their alloys, and the like. Focusing on steel, fabrication from grade 8 steel has produced structurally sound fasteners, whereas fasteners fabricated from grade 5 steel resulted thread stripping, and therefore should be avoided. Preferred embodiments include the use of high tensile or high strength steel or alloys thereof, capable of withstanding normal engine temperatures (195 to 276 deg.). 
         [0231]    The various portions of stud-alignment fastener  400  as shown in  FIGS. 4 ,  4   a ,  4   b , can be fabricated using a range of dimension values that will adequately function in the General Motors Northstar engine application as well as other like engine types. The following table (Table 2) delineates approximate dimension ranges (in inches) that enable the design and construction of several functional embodiments of stud-alignment fastener  400 . 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Overall  
                   
                 First  
                 Second  
                 Second  
               
               
                 Length 
                 Midsection 
                 Threaded 
                 Threaded  
                 Threaded 
               
               
                 (Feature  
                 Diameter 
                 Feature Length 
                 Feature Length  
                 portion length 
               
               
                 422) 
                 (Feature 416) 
                 (Feature 418) 
                 (Feature 414) 
                 (Feature 414a) 
               
               
                   
               
             
             
               
                 4.0 to 11.0 
                 0.38 to 0.60 
                 0.5 to 10.4 
                 0.5 to 3.8 
                 0.5 to 3.3 
               
               
                   
               
             
          
         
       
     
         [0232]    Stud-alignment fastener  400  approximate functional dimension ranges, wherein all values are in inches. 
         [0233]    Referring to  FIG. 5 , depicted is a sectional view of a detail of a threaded fastening/fastener interface  500 . The depiction assists in the understanding of threaded interfaces and provides a geometrical reference to defining nomenclature. Fastening/fastener interface  500  is comprised of bolt  501   b  coupled with tapped hole  501   a . Other depicted features include: major diameter (Dmaj)  502 , effective pitch diameter (Dp)  504 , minor diameter (Dmin)  506 , thread height (H)  508 , dimensional length 5 H/8 represented by feature  510 , dimensional length H/4 represented by feature  512 , dimensional length H/8 represented by feature  514 , dimensional length 3 H/8 represented by feature  516 . The dimensional length 5 H/8 represented by feature  510  is also referred to as the actual thread depth; the actual thread depth corresponds to the actual geometrical engagement between tapped hole  501   a  and bolt  501   b.    
         [0234]    Referring to  FIG. 6 , depicted is a front view  616  of combination aligning plate or combo plate  600 , having a feature corresponding back face  618  (not shown). Combo plate  600  is comprised of two mounting holes  602   a  and  602   b , one drill bit alignment hole  604 , and one tap alignment hole  606 . 
         [0235]      FIG. 6   a  depicts mounting holes  602   a  and  602   b  wherein the dual hole set is capable of accepting any combination of modified tapped hole bolts  608   a ,  608   b , or unmodified tapped hole bolt  610   a ,  610   b , such that combo plate  600  is capable of being securely fastened to any set of four engine block tapped holes  622   a  through  622   j  (shown in  FIG. 6   b ). Note that holes  622   a  through  622   j  will sequence through various combinations of original tapped and modified tapped holes as a user sequentially progresses in the retrofitting process. Additionally, combo plate  600  functions to provide a drilling and tapping guide so that corresponding processes receive substantially perpendicular support with respect to engine block face  620 . The drilling process is accomplished using drill bit assembly  612 , which is comprised of drill bit  612   a , and drill bit collar  612   b , wherein the function of drill bit collar  612   b  is to limit drilling depth. The tapping process is accomplished using tap  614 , which engages with tap alignment hole  606  possessing a corresponding thread contained therein. 
         [0236]      FIG. 6   b  depicts various combo plate  600  orientations and associated drill bit assembly  612 , tap  614 ; and modified tapped hole bolts  608   a ,  608   b , unmodified tapped hole bolt  610   a ,  610   b  fastener, combinations to mount onto the various engine block face  620  locations to enable the drill and tap process of engine block holes  622   a  through  622   j . The basic process is comprised of an initial drilling step accomplished using drill bit assembly  612 , followed by the tapping process utilizing tap  614 . 
         [0237]      FIG. 6   c  depicts exemplary dimensional aspects of combination aligning plate  600 , front face  616 , configured for use with a General Motors Northstar engine, commonly used in their Cadillac line. Exemplary dimensions include: combination aligning plate width  630 , having a preferred dimension of 6.0 inches; combination aligning plate height  632 , also having a preferred dimension of 6.0 inches; distance between mounting hole  602   b  and tap alignment hole  606 —feature number  634 , having a preferred dimension of 4.3 inches; distance between mounting hole  602   a  and tap alignment hole  606 —feature number  636 , having a preferred dimension of 4.0 inches; distance between mounting hole  602   b  center and right plate edge feature number  638 , having a preferred dimension of 1.0 inches. 
         [0238]      FIG. 6   d  depicts exemplary dimensional aspects of combination aligning plate  600 , side view, configured for use with a General Motors Northstar engine, commonly used in their Cadillac line. Exemplary dimensions include: combination aligning plate thickness  640 , having a preferred dimension of 0.38 inches; height of mounting hole  602   b —feature number  642 , having a preferred dimension of 0.43 inches; tap alignment hole  606  feature diameter  644 , having a preferred dimension of 1.0 inches; tap alignment hole  606  feature end to end height  646 , having a preferred dimension of 1.25 inches. 
         [0239]    Referring to  FIG. 7 , depicted are various components that comprise a cylinder head to engine block fastener installation or retrofit kit. Included as part of the installation kit of  FIG. 7 , is combination aligning plate assemblage  708 . The cylinder head to engine block fastener retrofit kit can be comprised from any combination of useful items associated with the installation or retrofit process, including:
       kit instructions or directions  702 , which is comprised from written directions, CD based directions, flash drive containing directions, dedicated website or webpage, or any combination thereof.   cylinder head washers  704 , washers are placed between the cylinder head nuts  706  and cylinder head  802 . An example of acceptable washers is case hardened steel 7/16 flat washer with black oxide finish available from the Fastenal Company, part number 302705-130481.   cylinder head nuts  706 , these nuts are used in conjunction with fastener  300 ,  400  or embodiments thereof, and fastened over cylinder head washers  704 . A typical nut or nuts are fabricated from grade 8 steel. Exemplary nuts are available from the Fastenal Company, part number 37889.   stud fastener  300 , and/or  330     stud-alignment fastener  400 , and/or  430     drill bit assembly  612 , comprised of drill bit  612   a  and drill bit collar  612   b ; an example of acceptable drill bit is the Silver &amp; Deming 17/32 bit, available through the Fastenal Company, part number 0316236. Drill bit stop collars are commonly available and function to limit hole drilling to a predetermined depth.   Tap bit; an example of acceptable tapping bit is the ⅝×11, available from the Fastenal Company, part number 0326680.   combination aligning plate assemblage  708 , the assemblage, or kit is comprised of combination aligning plate, combo jig, or combo plate  600 , including modified tapped hole bolts  608   a ,  608   b , and unmodified tapped hole bolts  610   a ,  610   b . Modified tapped hole bolts  608   a ,  608   b  are ⅝×11 type bolts, whose length are 2.5 inches, and available through the Fastenal Company, part number 110120419. The unmodified tapped hole bolts  610   a ,  610   b  are available via custom machining; specifications include M11×1.5 thread type with a length of about 3.350 inches, and hexagonal head is a minimum of about 2.4 cm from flat to flat.   Thread locking fluid  710 , an example of acceptable thread locking product includes Vibra-tite threadlocker  13150 , available through ND Industries of 1893 Barrett Dr, Troy Mich. 48084, or LOCTITE 262 threadlocker available through Henkel Industries of 32100 Stephenson Highway, Madison Heights, Mich. 48071.       
 
         [0249]      FIG. 8  illustrates a perspective exploded view of retrofitted engine  800  showing cylinder head, or engine cover  802 . Additionally illustrated are improved studs and associated fastening components in spatial alignment. 
         [0250]      FIG. 8   a  illustrates a sectional front view of stud fastener  300  mounted in an engine block modified tapped hole  250 . Height of stud  300  above surface of engine block  200  is depicted by feature number  804 . 
         [0251]      FIG. 8   b  illustrates a sectional front view of stud-alignment fastener  400  mounted in an engine block modified tapped-alignment hole  230 . Height of stud  400  above surface of engine block  200  is depicted by feature number  806 . Stud  400  alignment feature height above engine block  200  surface is depicted by feature number  812 . 
         [0252]      FIG. 8   c  illustrates a sectional front view of stud fastener with tool interface  330  mounted in an engine block modified tapped hole  250 . Height of stud  330  above surface of engine block  200  is depicted by feature number  808 . 
         [0253]      FIG. 8   d  illustrates a sectional front view of stud-alignment fastener with tool interface  430  mounted in an engine block modified tapped-alignment hole  230 . Height of stud  430  above surface of engine block  200  is depicted by feature number  810 . Stud  430  alignment feature height above engine block  200  surface is depicted by feature number  814 . 
       ADDITIONAL ADVANTAGES AND SUMMARY OF THE INVENTION 
       [0254]    One aspect of the invention is to repair a condition in the Cadillac Northstar engine where the threads in the cylinder head bolt holes corrode away over time, and strip. These cylinder head bolt holes are in the aluminum engine block. The original threads are too fine and it does not take much corrosion before the bolt will let go and lose its torque on the cylinder heads, thus causing head gasket failure, which these engines are very prone for due to this condition. 
         [0255]    The repair method used by Cadillac technicians and others is to drill out the holes in the engine block using a guide plate, re-thread the block and install an insert sleeve that is threaded both internally and externally, and then to re-use the original style head bolts. This repair is also very prone to failure communications with a sample of Cadillac technicians reveal that 4 out of 5 of engines repaired in this manner will fail again in a short period of time. There are many other aluminum block engines that exhibit this problem and the same repair method is used on those engines as well. The only other option known is to replace the engine block. 
         [0256]    One aspect of the present invention developed consists of drilling out the cylinder head bolt holes in the engine block to an even greater size inside diameter, specifically 17/32 of an inch, the entire depth of the hole. The hole is rethreaded with ⅝-11 UNC threads for the depth of 2.25 inches in each of the 20 holes. 
         [0257]    A custom machined, dual-diameter cylinder head stud is used as the repair. The large end of this custom stud is threaded into the newly re-threaded cylinder head bolt holes until the first diameter is recessed below the block deck surface approximately 1/16th of an inch. Left exposed and standing up 4⅛ inches above the block deck surface (different lengths on year model 2000 and up Northstar engines), is the smaller diameter of the stud, having a 7/16 inch diameter. The stud now acts as the original cylinder head bolts. The cylinder head gasket is slid over the studs, followed by the cylinder head, and then it is fastened down and torqued following the factory sequence guidelines to 75 ft. Lbs., using hardened flat washers and 7/16 inch inside diameter fine thread nuts that are taller than average, with an internal thread count of 20 threads per inch. Summary advantages of the present invention include: 
         [0258]    1. The threads in the block are much larger and much coarser than the original, which will ensure it will take more time before the dissimilar metals will cause enough corrosion to allow the stud to break free or “let go”. 
         [0259]    2. The cylinder heads can now be sequentially torqued from on top using the nuts, which helps to ensure torque accuracy as well as providing a gentle interaction with the engine block. In an engine system where studs are not used, the original bolts must rotate or twist under torque into the aluminum engine block, thereby risking damage to the soft aluminum block engine threads. When using the improved studs of the present invention, the threaded studs are fully engaged into the aluminum engine block before torquing or the fastening process starts, furthermore, stud threads located in the aluminum engine block do not rotate, thereby minimizing the risk of engine block thread damage. 
         [0260]    3. Due to their length and one piece design, the improved studs are easier and less time consuming to install than the commonly used threaded sleeve type insert systems, this enables some individuals to install the improved studs into the engine block by hand. 
         [0261]    4. The repair is a one-piece repair rather than a sleeve and the original style bolt. The stud will not exhibit any type of diameter expansion when torque is applied as the threaded sleeves often do, thus preventing the engine block from cracking or stripping the threads inside the threaded sleeve.

Technology Classification (CPC): 5