52mm vs 58mm Throttle body.

[Greg08]

i was about to say the same thing

A 52mm wouldnt work for a 355??

It may be a tiny bottle neck on that setup i guess.

[RamAir95TA]

A 52mm wouldnt work for a 355??

The term "355" in this case means nothing. That's just the displacement, 5 cubes more than stock. The impact on the engine's ability to breathe more air and fuel is practically immeasurable with those extra 5 cubes over stock. The heads/cam (in this case, a 355) dictate how much airflow is required - NOT so much the displacement.

Now when you move into the larger CIDs like 383+ then it becomes a consideration but for all intents and purposes a 355 might as well be considered a stock bottom end.

[Puck]

When the cubes are staying the same then RPM most importantly followed by VE will be the deciding factors on how much TB you need. Basically, a stock shortblock LT1 that's limited by the stock computer's RPM range will rarely if ever need larger then a 52mm...and even that is with a very stout H/C combo that can produce over 90% VE. Now, if your 355 is a nasty solid roller build spinning 8k then by all means go for the 58mm, it will make more power.

RPM is the most important factor for throttle body size. A high strung 7500+ RPM 355 will need a lot more TB then a street 383 spinning under 7k.

[Noah's95z28]

Good info guys, thanks a lot!

[1fstss]

if you run a 58 remember your intake opening is only 54mm... i run a holley 58mm on my SS (383 boosted) and i run a 54MM AS&M on the 355 in my Z28

[Casey96SS]

Just bringing an old thread up after doing some searching. Do you guys thinks a ported 52mm stock throttle body would be enough for my setup when it's done? (See sig)

I feel like I should make a step up over the stock TB since I will be running the LE ported intake.

After reading about the split blm and IAC problems with the 58mm TB's it kinds of sounds like something I don't really feel like fixing to make the car run right. Opinions?

[Fastbird]

More than enough. 48/52's have been proven up to near 500 RWHP.

[Casey96SS]

Cool thanks for the reply. I figure it's worth stepping up to a larger size with the 52mm. I'm trying to maintain as much reliability and drivability when I build my car as I can so the bored stocker is appealing to me. It's amazing how many threads are on all the different boards about TB's. It all seems to come down to some guy maybe making a few extra HP with a 58mm over a 52mm.

[SSlowBoat]

yes, dont buy into the 58mm witchcraft. we are still paying the price for putting the 58mm tpis throttle body on our stock bottom end LE2 build. after all the headaches it wasnt worth it.

[MI6TA]

I've seen some instances where the aftermarkets just don't measure up to a stocker bored out. There was a thread on this forum comparing the IAC's and that really convinced me that I'd stick with a stock TB.

IMHO if you're not a 383 don't even consider the 58mm. 52mm will feed you just fine up to 500hp which without power-adders is hard to come by. Go on Ebay and you'll find some remanufactured 52mm stock TB's for a decent price.