[Wichita-SCCA] Topeka racing invite

[Greg Laws]

Hi Dave,

I thank you for the invitation but the Phrog is torn down for a carburetor 
transplant and won't be back together in time.  It will be a most unusual 
swap -- perhaps unprecedented in all of automotive racing history.  I know 
this because there are no adapters available, no technical assistance 
printed, no nothing nowhere.  I'm entirely on my own ... again.  What is it 
with me and going down the path of total resistance?  Don't answer that!

Don'tcha just love it!   <grin>

Anyway, I've come to the conclusion that the Holley 350-cfm two barrel isn't 
doing what I need it to do.  The overall cfm size isn't too bad but because 
it opens both throats at the same time it gets too large too quickly.  In 
other words, it does great with top-end WOT situations but it isn't 
sensitive enough to deal correctly with low and mid-range situations.  The 
power curve is soggy until it gets wound up and I'm getting killed by the 
competition in terms of grunt coming off of corners.  I desperately need 
more mid-range torque!

In searching around for a solution I came across a most unusual carburetor 
to replace it with.  It is the Rochester Varajet 2.  You say that you've 
never heard of it?  I'm not surprised.  In the early years of the 1980s 
Rochester took their successful Quadrajet 4-bbl series technology (the carb 
that Jim Harrison runs on his 'Vette) and made a 2-bbl version, except that 
it wasn't just a Quadrajet sliced lengthways.  Nope, they took the basic 
Quadrajet idea of a small primary combined with a very large secondary and 
made it better.  It went on numerous small GM engines of the time, 
especially the small V/6 engines.  The carb that I'm working with came from 
a 1983 S-10 with the 2.8L V/6.

The engineers were struggling to make old technology engines meet new 
technology demands for emissions and fuel economy.  General Motors hadn't 
made the switch to fuel injection yet but it would be coming soon.  The 
Varajet 2 was the last gasp of sophisticated, complex carburetion technology 
in the face of the oncoming rush towards fuel injection.  The design of the 
small primary and accelerator pump was straight off of the Quadrajet only 
sized down for the smaller engines.  What was cool about the Varajet 2 was 
the design of the large secondary.  The engineers developed the secondary 
with a variable venturi combined with a variable jet, all operating 
automatically based upon air flow demands.  In other words, the driver could 
pop open the secondary with the throttle but it would never, ever bog.  The 
system mimics fuel injection in that the power is smooth and torquey across 
the entire rpm band.  It gives the engine exactly what it needs, when it 
needs it, and never more than that.  This was carburetion engineering at its 
peak.

The differences are stunning when one places a Holley side-by-side with the 
Rochester.  There the Holley sits -- simple, functional, completely 
understandable, and attractive.  The Rochester is probably the ugliest 
carburetor in the world.  It is complex and unfathomable.  It has little 
linkage rods going everywhere to vacuum pull-offs and choke shafts.  It has 
a strange, narrow & long footprint for mounting to an intake manifold and an 
equally strange top opening shape for an air cleaner to mount to.  Forget 
about ready-made adapters for either top or bottom -- you're on your own. 
The good news is that it flows 350 cfm just like the Holley.  The even 
better news is that it should fatten up the torque curve dramatically.  Or 
at least that's the theory.

I'll throw some photos of the thing onto my personal website if anyone's 
interested.  http://www.greglaws.info

Wish me luck!

Greg Laws


----- Original Message ----- 
From: ""-(©¿©)-Dave G"" <dgird at cox.net>
To: "Wichita Region SCCA." <Wichita-SCCA at wichitascca.org>
Sent: Friday, July 06, 2007 12:06 AM
Subject: [Wichita-SCCA] Topeka racing invite


> Anybody going to the PDX/SOLO at Topeka this weekend?
> If so, You can paddock with the Wichita  Reg  guys. Just look for the
> Yellow #99 Pos  ITB Pinto,or the awesome autocross/drag/PDX instructor's
> Grey CHEVROLET tow truck with the SINISTER BROTHERS RACING in the back
> window. Spectators, let me know before 3PM Friday so I can list You as
> crew, You'll get in free.
> Dave,still looking for a finish or two,,,still,Gird
>
> _______________________________________________
> Wichita-SCCA mailing list
> Wichita-SCCA at wichitascca.org
> http://wichitascca.org/mailman/listinfo/wichita-scca_wichitascca.org
>