Jim85IROC

iTrader: (2)

I heard good and bad about this piece. I heard that the throttle blades open too far, and that the TPS doesn't fit right.

I bought one. I haven't gotten the car running yet, but here's my opinion of the piece as it sits

My blades open exactly 90 degrees, as they should. The throttle linkage hits the body of the TB as a throttle stop. Works great.

I did have to file the tab on the TPS. It took me about 30 seconds, so I'm not complaining about that either.

One complaint that I have, although minor, is a stupid oversight that should get some moron fired. Instead of using the same thread pitch as stock, Holley decided to use a different thread size for their TPS bolts. Ok, an inconvenience, but at least it came with new bolts... too bad they were 1/2" too short The bolts they supplied were too short to even go through the TPS. Way to go Holley. Did anybody actually try installing one of these things on a car?

My other complaint, although extremely minor, is that you can't use the stock "TUNED PORT INJECTION" plate on the holley unit without grinding the back of it flat. I suppose holley wants you to have their name showing, but it would still be nice if I could have used my stock piece to keep the stock look.

Overall it gets an A- so far. Once the car is running I'll post more opinions.

Hecubus

Thanks Jim

I am looking into one of their TB's , but I was going to wait untill I heard some good news..

Keep us updated please

and pic's would be cool

Thanks

grumpyvette

DO I NEED A 58mm OR 52MM 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,(yes Im well aware some of you know even more than I do, but this is for the new guys)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 about637cfmthat 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 useand 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!

Jim85IROC

iTrader: (2)

I never proclaimed that I needed one.

My stock one looks sh!tty, especially now that everything else is polished. After breaking off one of the bolts that holds the IAC housing to the bottom of the TB, and not being able to get it out, I decided rather than hog the hole out and put in a helicoil, I'd just buy a nice shiny new one.

You're preaching to the choir about TBs being a wasted mod. If a 48mm TB is good enough for GM's 500hp 502 EFI big block, it's good enough for my (hopefully) 13 second car.

But... it is nice to see a voice of reason, especially when actually supported with math. So many people think this will help their performance, and it's a shame to see them waste the money when it could have gone toward something useful.

I remember a while back when GMHTP tested a 58mm TB on Tom Keliher's somewhat stock L98, they lost a couple tenths in the 1/4 by going to the bigger TB.

Hecubus

FWI

I'm building a 383 stroker/w AFR 's custom ground large cam, all fully ported and polished intake and ATI Disc procharger bla bla all the goodies

I've heard this story time and time again ..I think you are right on stock applications!

But the Track #'s dont lie
Friend of mine is running a P1SC Procahrger on a mildly buillt 350, ported intake, he finally got around to putting on a 52 mm TB and gained .2 Solid and constant.

I do agree with you on most stock applications .. But I too think you're preaching to the chior

I'm strictly going off of several others results and all have been good who actually need it

Jim85IROC

iTrader: (2)

nobody is saying that there's never any use for them. Obviously with forced induction pushing high horsepower levels, you're going to have a completely different situation.