Some very good points Shane,
I do have a correction to make for my earlier post though, when I mentioned
that1000cfm was for engines starting at 350hp, I made a misread thier lit.
The System they had was designed for 350 ci engines UP TO 450 hp. As for the
other info, I did not just pull it out of my a**, I actually checked with
Rance Fuel Injection in PA. They recommended 1000 cfm TB's for all engines
with 300+ hp.
You have to remember that most of these aftermarket companies deal with
"gross" hp figures, not "net". If you take a stock 318, add a good set of
headers, a free flowing intake, and an aftermarket computer, you will be at
300 hp "gross". The engine still needs to breath, even with a stock cam
(which, by the way, is the same cam used on the 300+hp 360 crate motor). I
have tested stock, modified stock, 50mm polished, and 52mm polished TB's
before I swapped heads and cam on a stock 360 engine also. Everytime I
stepped up, there was a measurable difference. This leads me to believe that
my engine would respond to a 53mm TB quite well.
Which leads us to Sam's original question, would a 53mm TB work on a built
360? Of course it would, throttle response was never an issue on my truck
before my current mods. My 360 was typical of others that are doing 360
swaps to thier Dakotas.
I do agree that in cases where people do not step up the cam, a 53mm tb may
be too much, in that case the cam is a limiting factor. When we tested Sam's
truck at Milan Dragway, there was a limit he reached with his stock cam.
Once he hit 14.10's there was no more that could be done to the engine to
gain extra horsepower. We did swap in a hogged-out beer barrel, 24lbs
injectors, and a 52mm TB, but never gained any additional horsepower on his
318. However, on my stock 360, those same mods did make a difference. 42
extra cubes and better valvesprings allowed me to spin my motor 500 rpms
higher and take advantage of the extra breathing these provided. I do
suspect that if Sam swapped his valvesprings for some fresh ones (and/or a
descent cam), he might have gained an advantage with the 52mm TB above 4500
rpm.
You make a point about velocity, if you spend all your time below 3500 rpms,
then there will be better torque with a smaller TB, but at that point it is
a restiction and it will cost you horsepower above that. I guess its just
apples and oranges, I prefer oranges. And as for testing TB's with
supercharged engines, the SC is pushing air through and is less sensitive to
changes in TB size, however, pull-through SC's like the Kenne Bell would
respond differently to large bore TB's, smaller ones might limit boost.
I guess thats all I have to say on this subject, not all of us will agree on
the 53mm TB, but the diversity of our opinions is what makes this list
great. Hopefully, many can learn from the mistakes of the few, and I have
made enough myself, but I do learn from them.
Mark Kuzia
flyboy01@mediaone.net
http://people.mw.mediaone.net/flyboy01/home.html
1995 Dakota 13.79 @ 102.45 mph
360ci, 5-spd, 4.11 LS(8 3/4 coming soon), Cowl-induction
(A new E-body 8 3/4 [3.90 SG] has been built by Reider Racing)
http://www.twistedbits.net/WWWProfile/dakota/FqNiqqo2UjQOY/
> Uh.....in my opinion Mark, you and a few others are the exception rather
than
> the rule as the majority stay under 3500rpms. We are still talking about
> "street" driven trucks huh?
> Other than being an air metering device - they exhibit a few flow
> characteristics mostly recognized by their WOT flow characteristics. At
WOT -
> this is simply an orifice. Some are bigger - some are smaller. Some have
a
> venturi shape, some have a straight bore. Some attempt to change the way
the
> air flows at high rpm, some affect the low rpm more. These are where the
real
> differences are - not in the friggen size of the hole.
>
> For example, take a 4800lb truck and run it in the eighth mile. This is
pretty
> typical of whats going on w/most Daks in a street-light to street-light
type
> situation. Guess what? I'll bet on the one with the stock TB everytime
given
> everything else being equal. Why? Because the smaller bore stock TB has
much
> better flow characteristics at lower rpms. Think about air speed - not
air
> volume. The stock TBs have faster air speed than a larger bore TB.
Imagine how
> much slower the air flows in a 53mm TB vs a 48mm TB at say 1800rpms. That
> smaller orifice and especially that venturi design will cause the speed of
the
> air to be faster than the air moving thru that 53mm TB. This works just
like a
> mini-supercharger - and results in more air in the cylinder at the same
rpm.
> Light that fire and the stock TB will kick the 53mm TBs butt everytime. >
Testing TBs on a supercharged V6 (assumption) is almost completely useless
to
> this group as far as I am concerned because I can't think of but maybe one
other
> individual (ViperTruck or something like that?) that might could even use
the
> results. I would rather see a test of a bone stock (ok maybe a few
typical
> mods) trucks (Reg -vs- CC, 3.9/4.7/5.2/5.9L, auto/manual, 3.55/3.92/4.10,
etc)
> w/a stock TB, vs several other TB designs in a 1/4-mile, 1/8-mile,
1000-ft, and
> 60-ft type scenarios. These results might be more valuable to a larger
crowd.
> I think you might be surprised of the results.
> Latr,
>
> Shane
>
> --
> '96
IndyRam-HisIndy-MPI/TB/Pulleys/AccelCoil/MPComp/HookerSuperComps/CompTAs
> '96 IndyRam-HerIndy-numbered(#142)"Track Truck"
> '74 Triple-Black Dodge Challenger Rallye 360 home-brew EFI R&D vehicle
> '68 Black Corvette Convertible 427 (For Sale)
>
>
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