i got the h.o. manifold for my 97 2.4 and was wondering what size is best for performance? ive seen alot of post saying 56mm and 62 mm and so forth. was wondering how much diff is there between the two and which one is better for for stock swap, or turbo etc.
ive heard alot of different opinions but one idea is seeing that you have the HO mani. and the 2.3 t.b. is 56mm compared to the 52mm stocker you could go with the 2.3 t.b but ive also heard guys goin with a 62mm and goin right back to stock, some would say bigger isnt always better.

15.2@89mph 2.171 60ft. 9.830 1/8 R.I.P. "LULU"
I'd say to go with the 56 (check classifides, where I just saw one) for now and when you do your turbo you can upgrade to the 62mm.
I love my 56mm on my HO swap, but I can't compare because I have never used the 62mm which infact is actually at 61mm messured by so many of us j-tuners. My 56mm has a really nice sound to it and you can tell it pick up a bit in the topend. So my opinion is go with the 56mm. If it was not a good TB GM would have not of put it on their 2.3HO setup would they?
In the planning stage for an all American TRD Cavalier.
i took off the mani with the t.b. on it. what size is the one that is orignally on it.?
a 56mm comes with the HO mani, and a 52 with the Stock 2.4 manifold (plastic one). 56mm is probably the best N/A bet. while the 60ish + could see more potential on a boosted application.
My Cav
I give up...
i'm buying a VW those people love trees, so they should love eachother too... "Andy"
Bigger isnt always better, this is true because there are high horsepower cars still on stock throttlebodies (some Grand Prix turbo cars for example)
The 56mm is probably youre best bet until you go boosted or build the snot out of your engine. Anything bigger and you start losing power... If you want proof or at least some theory to back it up search for posts by madjack about Volumetric Effeciency (VE).
I would also say a 56-57mm is the best size for a LD9 NA car. I'm running a 57mm TB.
FU Tuning
whats the best for a turbo'ed ecotec?
You take a women and X her by PSI devide the legs and you can then juice the car......LOL
The bigger the throttle body the better (within reason) for boosted applications. Since you are FORCING air through you dont have to worry about a lot of the same issues you do when the car isnt boosted. So, if i were stuck between the two i would go with the 62mm. You could probably go bigger than that though...