From: hotrod@dixie.com (The Hotrod List)
Subject: Re:  gears
Date: Fri, 22 Jan 93 00:09:29 GMT
Organization: Dixie Communications Public Access.  The Mouth of the South.
To: hotrod@dixie.com
Reply-To: hotrod@dixie.com
Posted-Date: Thursday, Jan 21 19:09:26
X-Sequence: 3573
X-Gifs-To: met@sunset.cse.nau.edu
X-Gifs-From: ftp.nau.edu

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.

>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.
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...

Interesting discussion, eh?
JC.   jca@fibercom.com

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Posted by: emory!fibercom.com!jca (J.C. "J. Hoss" Akers)
Newsgroups: alt.hotrod,wiz.hotrod