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Intake question: Ken do you know?



I did a search here on 52 mm throttle
body and found a passage Ken quoted from.
It's from www.c4vettes.com under performance.

Anyway, it says that the 52 mm throttle body
is not a help for the L98 because the input
runners are too restrictive.

My question is, what about the LT-1?
TPis says that the stock 48 mm TB flows
668 cfm, with the air foil 710 cfm. The 52 mm
TB w/airfoil (the sell it this way) is
supposed to flow 835 cfm.

So can my LT-1 with stock cam and heads
gain anything from 835 cfm as opposed to
stock? Can it even benefit from 710 cfm
as opposed to stock? Will it benefit from
835 cfm as opposed to 710 cfm? It all depends
on the intake system...

I'm trying to decide if I should get the TB or
the airfoil or just for get it and go for ignition
mods like the MSD-6A. (Yes, I will do some exhaust mods but waiting to hear it at Carslile)



Gone but not forgotten
Jan 30, 2001
Hermosa Beach, CA
1987 Z51 Silver Coupe
A 52mm throttle body will help your LT-1 breathe easier, and it certainly wouldn't hurt, but anything larger is overkill for your application. If you get into a stroker motor, or change intake/exhaust systems, then a bigger throttle body would be called for.

I hope I answered your question.

_ken :w


Thanks for the comparison. So you
do mean that anything larger than
the stock 48mm TB will be more than

Also, from your knowledge of TPI systems,
would you say that my hypertech chip
(must be close to stock) would be
able to keep the mixture from becoming
too lean at wide open throttle?

--I would be a little worried about knock,
as with the hypertech chip my knock sensor
is already active. I have no knock at all,
but only because the sensor is saving me.


I forgot to mention that
I do have an SLP claw for
induction (3 K/N airfilters,
no airbox), so I should be
slurping more air than stock.

That was why I wanted to maybe
try the 52mm TB.

I appreciate your help,
Thanks a million!


Well-known member
Apr 17, 2001
Loxahatchee, FL, Palm Beach co
."DO I NEED A 58mm THROTTLE BODY on my TPI 350 to get better performance"

I get this question about once a week in my E-MAIl

ok time for a math lesson, please try to follow along,the stock throttle body flows about 670cfm,
your 350 in the vette has a stock cam that has about 210 dur and lets be even more generous and say the heads flow 210cfm and your TPI intake also flows 210 cfm (to keep things simple, trust me, your stock heads, intake and cam don,t flow that well combined) now that means that at a steady flow rate with all the ports open at max cam lift for 360 degress of engine rotation that possiable durring the intake stroke your flowing 210cfm per intake port, correct (again being very generous) now in a standard stock engine theres 360 degees available in an intake cycle if the valve never closes (bad for the compression stroke) so about the most those ports can flow if the valves open instantly and stay open the full 210 degs at max lift is 210cfm/360 degs x 210degs the cams open or about 122.5 cfm x 8 cylinders=980cfm but since those valves open and shut durring the cycle your only able tp flow at about 65% of the max for a flow rate of about 637cfmthat well under the stock throttle bodys flow,
lets look at it from a second angle, your TPI 350 spinning at about 5500rpm (where it starts to run out of airflow big time) if the cylinders fill completely on every intake stroke(which remember is every 2nd stroke)is 350cid x 5500/2=962500 cubic inches or divided by 1728 to get cfm=557 cfm
now even if we add a 30% better flow due to exhaust scavageing, and ram tuning the intake pressure waves and a more realistic 35% reduction in intake flow due to the valve needing to open and close ,(not being instantly fully open the whole time)thats still an average of (557+637=1194cfm+10%=1313/2=656cfm,is about max the engine can use and in the real world its slightly less in a stock engine, and thats not counting for airflow volume losses due to heat expansion or restrictive losses due to the screens on your M.A.F if you still have them and are not running a speed density TPI or the air filter restrictions or the catalitic converters partly screwing up the exhaust scavageing.
now for the good news, unlike a carb system that relies on air flow to carry the fuel air mix, EFI can and does run better with a max possiable intake pressure behind that intake valve, adding a 52mm or 58mm throttle body will effectively add slightly to your potential air flow and reduce the systems airflow restrictions and unlike a carbed system its extremely difficult to add a throttle body thats so large that it screws things up,so if you want to add a larger throttle body ,go right ahead, it may not help (on a stock engine) but its almost never going to hurt either, but after much testing Ive got to say, if your talking about a stock engine spend your money on a 383 stroker kit, better heads,a better flowing intake manifold, headers, and a larger cam in the 220-230 durration range before worrying about a throttle body restricting your hp!


I assume that by a TPI 350 you are including
my LT1, I have read some people who write
"TPI 350" and mean an L98 only.

So I take it the 210 cfm for the heads, cam,
and intake manifold are LT1 numbers?

At the end there you do mention that I could
"reduce the system's airflow restrictions"
with the 52 mm TB. Now, I have an SLP induction
system (3 K/N filters naked over the shroud,
no airbox, air is picked up and flowed directly
to the TB), so would the TPIS airfoil then,
which is supposed to up the air flow capacity
from 670 to 710 cfm, would that do some good?
Would that have the same result as the 52mm
TB because I have all the air the engine can

Thanks!!! so much, for saving me from doing a
wasteful mod. Seems like there's a lot of
them out there.


Well-known member
Nov 12, 2001
San Diego, CA
1992 Convt w/hard top; 2004 Z06 Z16; 1962 327/300
Just for a twist on this.....
What e/h? (Extrude Hone -sp) Has anyone had this done to the stock intake?? That is supposed to increase flow a fair amount.

It can be done the the heads and exhaust also.



Well-known member
Apr 17, 2001
Loxahatchee, FL, Palm Beach co
no, TPI means just what it says L98 not LT1, a relatively stock LT1 cannot use a big throttle body either but once you stroke a LT1 or l98 to 383 or larger and port the heads OR GET BETTER FLOWING HEADS and add headers and a cam you get to the point WHERE YOU MAY NEED THE BIGGER THROTTLE BODY , figure that if your not over 425 flywheel hp your highly unlikely to need a larger throttle body.


Well-known member
May 23, 2001
1985 Bright Red Rocket
I agree with Grumpy. I talked to a Holley Rep at the last car show and he (Along with a guy from Campbell Engines) explained to me in less detail about the exact thing

NOT TO MENTION Holley is OUTRAGEOUS on the 58mm Throttle Body even the Rep thought it was high..

In the upcoming years Ive decided to go with a 383 Stroker with Lunati guts.. (Not sure on specifics yet..) a Comp Cam (Again no specifics Im still learning) , TPiS Headers (Coated), TPiS Mini Ram, Custom PROM, and when Im rich and famous again LOL a richmond gear box..

Ive done alot of studing with this site among others with the opinons of race mechanics and the setup that seems to be ultimate is not unlike Ken's or 69MyWay's setup.

Eventually I'll be able to afford these mod's and thats the setup Im shooting for..So anyway after all that then I'll look at the 58mm throttle body.

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