hey i was wondering which throttle body size would be better for a ported edelbrock/slp tpi (ported and welded by dr j performance) slp cold air intake gm hot cam and afr 195 on a fresh 355 block.. this combo should produce around 350 to the wheels and would 24lb injectors and a afpr be enough injector for 350 wheel power.... thanks in advance..

 

go with a 58mm throttle body and 24s should be good enough. btw what fuel pressure you running your car at.

 

A bigger TB on even a modded 350 TPI isn't necessary as a TPI, by design, is not for revs. A stock 48 w/a foil flows over 700 CFM which is plenty for a 5500 RPM engine. Now, an engine with a HSR, Mini Ram, etc. is a different animal. TPIS claims they can make 450 HP with 22 lb injectors, at an elevated pressure, so 24's should be plenty. Spend the $300 from the TB on a razor sharp tune. That'll make the biggest difference.

 

well in my own personal expereince i had best results with a 58

 

58mm tb is way over kill. Run a 52 mm tb at most. I run a 52 with great results

 

well my throttle body is over 20 years old and im sure it needs to be serviced..... how do i serivce it to make it like new again....... but i really want a new 52mm throttle body...

 

go to autozone or pepboys and they sell a rebuild kit. its simple just a few gaskets and orings. make sure you also get a bottle of carb cleaner. i like brake cleaner best even though it aparently breaks down rubber it cleans parts so much better

 

Check the throttle shaft to throttle body bushings for wear and slop. excessive wear will be an vacuum leak past the bushing and will make the butterflies stick in the holes.

There are guys that can repair this area but the cost is about that of the upgrade.

on the auction site:

extreme-fi sells remanufactured TPI TB bored to 52 mm for $150.00 or 54 mm for $180.00.

CNC motor sports has some billet TPI TB 52/56 mm for $175.00

I have no experience with these.

 

Just a note, I had inconsistent idle with my 25yr old 48mm TB, so I put a new BBK 52mm on and the idle is smooth and steady now. I just bolted it on and set the TPS to .54 volts. It was well worth the $309 from Summit. Its been years since the Z28 had a good idle. I always thought it was something else and replaced a bunch of other parts. The old TB was flat-*ss worn out all this time...LOL