652 Oliver Street 

Williamsport, PA 17701 U S A. 

717/323-6181 

MANDATORY I 1 

DATE: November 26, 1976 Service Bulletin No. 393C 

(Supersedes Service Bulletin NO. 393B) 

Engineering Aspects are 

FAA (DEER) Approved 

SUBJECT: 

MODELS AFFECTED: 

Exhaust Slip Joint Modification 

TIGO-541-E series engines with serial numbers 101-62 thru 698-62. 

Remanufactured engines shipped before September 15, 1976. 

NOTE 

Engines that were inspected and modified in accordance with any previous 

edition of this bulletin NO. 393 require only the cable change as 

described in step 6. 

TIME OF COMPLIANCE: At next 100 hour engine inspection except engines modified in 

accordance with Service Bulletin No. 378 in which case change is 

required in next 25 hours. 

Three previous methods have bee" used to 

prevent separation of the exhaust pipe slip 

joints at the rear of the left and right 

exhaust manifolds. Briefly, Service Bulletin 

No. 368 describes a spring tensioned rod and 

clamp device while in Service Bulletin No. 

378 a U-bolt clamp assembly and slitted 

adapter pipe was used. Earlier editions of 

this bulletin provided for a single then a 

double cable assembly to replace the spring 

tensioned rods and U-bolts. Since then, severa1 instances of stretched cables have occurred indicating that the previous l/16 inch 

single and double cable assemblies used were 

insufficient to secure the manifold; consequently, this edition provides a larger single cable (l/8 inch) at each location. Proceed with the following instructions insofar 

as they are applicable to the engine being 

modified. 

3. Reassemble exhaust adapter pipes to 

transition assembly using new 78083 

kets. Check coupling part "umber. MVT69183- ?=,- 83- 

200 Avco Lycoming P/N LW-12093-5 is the 

number of the correct coupling to be used. 

Inspect the 3 v-band sections of each 

coupling with a depth micrometer as show" 

in figure 2. Any dimension obtained under 

.230 inch renders the coupling unfit for 

further service. 

1. Remove spring tensioned rod and clamps 

or u-bolt clamps as may be the case. These 

parts are not reused. 

2. Inspect exhaust adapter pipes for cracks 

around flange fillet and slits. (Pipes with 

or without slits may be reused.) Pay particular attention to condition of slip joint, 

noting any damage which may prevent free 

movement of the joint. I" addition, check 

the end of the adapter pipe inside the 

flange mouth; it must be .090 inch below 

the surface of the flange face. Use a hand 

grinder if necessary to obtain this clearance. (See figure 1. ) 

LW- 13027 or LW-IO798 REAR EXHAUST ADAPTER 

Figure 1. Exhaust Adapter Pipe Showing 

Areas Requiring Inspection 

Page l of 3 
Service Bulletin No. 393C

4. Before installing the couplings around

the adapter pipes, make sure the entire

exhaust assembly is in alignment; that is,

mating flanges must match each other. Support the exhaust system in this position

and proceed to install couplings around

flange and engage latch. Tighten coupling

nut to 50 inch pounds initial torque. Tap

outer periphery of coupling with mallet to

distribute band tension.

5. Check torque and continue tightening to a final torque of 70/80 inch pounds, tapping coupling until torque reading stabilizes.

NOTE

Do not exceed tightening torque specified for couplings, or open them far

enough to damage the coupling wrapper. Over torqueing spreads the v- band section of the coupling and

impairs its retaining qualities.

INSIDE DEPTH OF

CLAMPING AREA

MUST NOT BE LESS

THAN .230 IN.

Figure 2. Exhaust Manifold Coupling

Inspection Requirement

NOTE

The exhaust adapter pipes attached to

nos. 5 and 6 cylinders, along with

the segments attached to the transition assembly, are especially subject

to cracks in the area of weldments

and attaching flanges. Replace any

that indicate such defects.

6. Assemble clamps LW-14504 on adapter

pipes approximately 2 inches from slip

joint and LW-14525 clamps on left and right

exhaust pipes. Connect cable assemblies LW15437 to clamps with attaching parts STD2177 bolt, STD-2178 washer and STD-2044

nuts. Note that 4 of these new LW-15437

cable assemblies, which are now 1/8 inch

diameter, replace 8 of the previously used

LW-14572 cable assemblies that were 1/16

inch diameter. The indicated quantities are for 2 engines. Attach these cables, leaving

enough slack to provide 1/4 inch deflection

of the cables after assembly. (See figure

3.) Tighten nuts to 60 + 10 inch/lbs.

NOTE

The following kit to perform this modification is supplied through Avco

Lycoming Distributors. Parts must be ordered before February 1, 1977.

Allowance for labor and full part credit, F. O. B. Williamsport, Pa. will be

provided in accordance with the following schedule. Furnish engine serial

numbers to your Avco Lycoming Distributor for ordering parts and submission

of a Warranty Application.

1. Engines in compliance with Service Bulletin No. 378 . . . .3 hours labor

2. Engines in compliance with Service Bulletin No. 368 . . .. 1 hour labor

No allowance for labor is provided for engines that are in compliance with

Service Bulletin No. 393 or 393A; however, 4 cable assemblies, LW-15437 will

be furnished at no charge directly from Avco Lycoming Service Department.

Include engine serial numbers with your request for the cables.

Page 2 of 3
Service Bulletin No. 393C

NOTE: CABLES ARE ATTACHED OUTSIDE

OF THE CLAMP.

STD 2177 NOTE

RIG CABLES (LW-14572) TO PROVIDE

1/4 INCH DEFLECTION WHEN MEASURED

MIDWAY BETWEEN CLAMPS-BOTH SIDES.

CABLES ARE ASSEMBLED ON THE OUTSIDE SURFACE OF THE CLAMPS AS

SHOWN IN THE INSERT.

STD-2044

LW-14525

Figure 3. Area of Transition Assembly Showing Cable Assembly

PARTS DATA:

Kit No. LW-14608 Exhaust Manifold Retainer (for 2 engines) consists of:

Qty. Part No. Description

4 LW-14504 Clamp, exhaust pipe, 2.10 in. I. D.*

4 LW-14525 Clamp, exhaust pipe, 2.00 in. I. D.*

4 LW-15437 Cable Assy.

8 STD-2177 Bolt, 1/4-20 x 15/16

8 STD-2178 Washer

8 STD-2044 Nut, self-locking

4 78083 Gasket, v-band coupling

* - Inside diameter of clamp is measured with .20 gap at opening.

NOTE: Revision "C" changes cable assembly and quantity required.

19025, 19025-A, 19434, 19591 - These numbers for Avco Lycoming reference only.

Page 3 of 3