[Tigers] Stub Stack and the other flow device

[Ronak, T.P. (Timothy)]

Jere,
I am still lurking here ... miss my car :(

I do have a bunch of real world experience and will try to refresh some on
what we did a while ago at CAT Dyno days as well as some stuff back when we
ran GT-1 with Theo in Calgary.

The real issue with the Tiger as you get beyond the 275HP range is that the
airflow starts to become a limiting factor due to the proximity of the choke
housing to the lid of a stock Tiger. As I recall at the closest point it was
only less than a quarter of an inch from the lid and as you increase the power
output you increase the air demands placed on the inlet of the carb. While a
stock Tiger might not see any gain from improving airflow at a 165 HP output
level as you get to 300HP+ you need to start exploring ways to improve this. I
did notice a small gain in how well the car ran with a K&N in the stock trim
with the mild cam my car had and the assumed 225HP level. The filter was still
way too small. I wound up with a custom built base for the air cleaner
integrated into a ram air box sealed to the LAT hood scoop and a 2.25 inch
tall 14 inch diameter filter that used the stock Tiger air cleaner. It is also
important to note that my Motor mounts were through bolted to minimize engine
rotation and the subsequent tapping of the oval air cleaner on the hood. The
air cleaner filter element could maybe have been another .25 inches and still
cleared the LAT and factor hood. The steel hood I believe actually allows for
more air cleaner clearance as it is overall a thinner material and does not
protrude down as far into the engine bay but that is guessing right now.

Jere mentioned a Holley Stub Stack although that was not the device we tested
... it was called an Air-Horn and it mounted with a conical shape under the
air cleaner lid on the air cleaner stud with the narrowest part of the device
pointing into the carb. We tried this when I had the basic Holley 750 on my
stroker motor. Jere recalls correctly that it did not create any measurable
gain. The Actual Stub Stack was something we ran on our Race Car and in fact
in created about an 8 HP gain for us on a 350 ci Chevy making 620 HP but this
was in the days of NO POLISHED CARBS WITH THE CHOKE HORNS MILLED OFF> now a
days I would opt for a chokeless carb if you are looking for power and this
eliminated all of the issues of airflow for me as it dramatically improved the
distance from the air inlet to the underside of the upper air cleaner lid. We
did try a Holley stub stack on a relatively stock engine and found no gains as
the air demands were relatively meager and the marginal gain was less than
what could be statistically measured on the dyno device we were using.

Rather than smoothing airflow .... in my opinion .... the search for free
power rests in the fact that for every 10 degrees you reduce air inlet
temperature in any given environment to the carb you typically gain 1 HP due
to the denser charge of oxygen as most Ram Air proponents suggest .... A
sealed ram air device is the cheapest and most cost efficient approach to HP I
know of for an already built system. This effect is of course coupled with the
pressure increase from a air intake system and the 'RAM' effect of an air
scoop that may provide some additional HP benefit.  If you consider that the
average engine bay operates in the range of 190 to 220 degrees (or higher) if
you are seeking real free power simply ensuring ambient are temperature from
the Atmosphere reaches the carb then on a 90 degree day you can create a
'found' 10-13 HP through the cooler and more dense intake charge available
with a sealed ram air type system drawing air from outside of the engine bay.
Best Regards,
Tim Ronak
Senior Services Consultant
AkzoNobel Automotive and Aerospace Coatings NA
23961 Via El Rocio
Mission Viejo,  CA  92691
Ph: (949) 289-3357
Fx: (425) 955-6268
EM: timothy.ronak at akzonobel.com<mailto:timothy.ronak at akzonobel.com>
Personal EM: timronak at cox.net<mailto:timronak at cox.net>

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