From: hotrod@dixie.com (The Hotrod List)
Subject: RPM's and Gears
Date: Fri, 22 Jan 93 14:43:38 GMT
Organization: Dixie Communications Public Access.  The Mouth of the South.
To: hotrod@dixie.com
Reply-To: hotrod@dixie.com
Posted-Date: Friday, Jan 22 09:43:25
X-Sequence: 3579
X-Gifs-To: met@sunset.cse.nau.edu
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Dennis responds
> JCA wrote
> > Dennis writes:
> >.JCA (me) wrote:
> >> My best friend runs 5.30s in his [street legal] pro-stock Plymouth...
> >> but it is a strictly 1/8th mile car...  man I thought _we_ were radical!
> >
> >Mopar are more torque engines than small block Chevey engines.  Some of the
> >modern small block race engines are turning 8,000 plus rpm's.  Most mopars
> >loose there bottom end a little over 6,000 rpm's, unless radically built up.  
> 
> Although I am a firm Chevy man for drag racing, I hesitate to categorize 
> any particular manufacurer's engines as weak or strong...
> The mopar engines I have known (I haven't owned any personally)
> have been stronger than Hell!  A friend has run a 340 in his Barracuda drag 
> car for several years that he _launches_ at 9,000 RPM and shifts at 
> 11,800 RPM!!!!  He also has a B1 Wedge motor that he runs to 10,000 RPM.  
> Of course my best friend used to shift his LS-6 crate 454 at 7500 RPM 
> without any problems.  Another friend shifts his 327 Chevy II wagon 
> (street car) at 8,500 RPM.

Now may I ask if these are stock engines.  I have seen quit a few  stock 426
wedges and 440's that dropped there bottom ends.  I also know of a couple
Hemi's that had complete bottomends put in and are shifted at 10,000 rpm's.
 with
> 
> >The big thing is why waist your dollars putting in a cam that gives you 
> >the ability to crank 6,500 or 7,000 rpm's if you never will crank more
> >than 4,500 rpms on an engine.  
> 
> I agree with you here...  on the "street" the most durable power solution
> is a high-displacement engine that is very mild, making it's power below
> 6,500 RPM.  
> 
> >My friend now is using 5.5 gears on his Chevelle with a 454 that is heaviely
> >reworked.  He is not having any problems turning  130+ miles per hour and
> >keeping his ET's under 10 sec.  However he does not use this machine daily
> >on the street.
> 
> I guess where my basic disagreement comes in is that lower gears is not always
> the correct solution to a performance problem.  Many years ago my '68 396 
> Chevelle was set up with 3.30 gears with a basic "torque" engine configuration.
> (made all of it's power below 6,000 RPM)
> Because my street tires were so short (245 60 R 14s  - had ~24.5" diameter)
> The car actually got slower in the quarter when I switched to 4.11 gears.

Sounds to me like too much torque and not enough bite into the pavement.

> Then I changed the engine configuration to a power setup with larger cam,
> tunnel ram, two 660 Holleys, etc.  The engine (I don't own it anymore :-(
> now easily turns 7,500 RPM.  For a "real" street car, who wants to drive
> the speed limit at 4,000 RPM?  I guess one of the things that should be
> in the equation here is the tire diameter...  it has an _incredible_ 
> effect...  Let's see, the equation goes something like:
> 
> (MPH * Final Gear Ratio) / (.002974993 * tire diameter) = Engine RPM
> 
> With this equation, assuming your friend has 29" slicks (typical)
> he would be turning 8287.5 RPM at 130 mph.  (no this does not take
> into account the slicks "growing" or losses in the torque converter, etc)
> That number is not unreasonable for a BBC...

Actually there 30 inchers but thanks for the support.  It seems like 45
souls out there cannot believe that anything over a 4.11 is a performance
axle.  Guess there more interested in the salt flats than minimizing there
ET's.
 > 

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Posted by: emory!picard.med.ge.com!bednarek (Dennis Bednarek Mfg 4-6971 ~BHOSVWZ#097)
Newsgroups: alt.hotrod,wiz.hotrod