After a quick search, I didn't find anything definitive. At this point I'm thinking that throttle body choice might be just a huge grey area for these cars, but I'm going to throw this out there anyway.

Money is an issue here, if a 52 mm throttle body will suffice for what I need, then I'll have the stock one bored and save some money. However, if the 52 is not big enough, I'll have to spend the extra money on a 58- which I don't mind doing because after coming this far I don't want to skimp now.

Here's some info on my combo-
11.3:1 compression, heads flowed in the mid 240/180(no pipe) range before valve job and backcut, intake manifold is port matched, cam is a custom comp 236/248 .608/.578 111 LSA, 38 lb/hr injectors Hooker long tubes/Y-pipe. That's all the air delivery stuff I can think of now to list, if I've forgotten anything just remind me and I'll post it.

I don't really want to "just get by" if I can with a 52 mm, if I need a 58 that's no problem. I'll rev the motor until it starts hurting acceleration, or until the stock PCM cuts me off, whichever happens first

 

My opinion is,get the 52.Unless you are going to spray,then a 58 might help.

 

I didn't list it because I didn't think nitrous would affect TB choice, but I am planning on spraying later. I didn't forge this motor for nothing

 

Buy a 58 they cost the same. Bolt it on without ported the intake for now and then port it out to 58 later if you want. I don't think it makes a huge difference in et or mph to not port the intake right away with a 58. I am running it on my car currently. Seems to work just fine. Thought the blades would stick but apparently not .I get full throttle and all seems well. I figured why not get the bigger one and just do it this way.
The argument is pretty loud on both sides some saying the engine can't use it and some arguements showing dyno improvements ,I have seen some in the mag tests showing the bigger tbs did add hp even on pretty stock combos.

Its maybe like buying bigger injectors for later on ,as long as you have tuning you can run the bigger injectors. Well bigger injectors cost more money but tbs are the same for 52 and 58 or at least very close to the same price.

 

He said if he goes 52mm he will have a stocker rebored which cost HALF what a new one cost. Putting a 58mm on a 54mm intake is foolish even the most basic understanding of airflow will allow you to see that.
Since staying 350/355 I think a 52mm will suffice though I think there is someone who managhes to get 54mm out of select stock cores. Small diameter changes can equal large flow changes.

 

Does anyone have flow numbers on the different sizes of throttle bodies? Flow numbers for stock, other stock applications(like LS6) and aftermarkets MAF sensors would also be helpful just for comparison.

 

Alright, I kind of answered one of my own questions from reply above me^. From another thread in the advanced tech section-

I have the screen out of my MAF, and I'm thinking almost 1000 cfm will be sufficient for my combo (not 100% sure, if I'm wrong let me know), still wanting to know what kind of flow the 52mm and 58mm TB's are capable of.

 

Port you stocker yourself. I remeber someone on ls1tech doing it maybe you can find something over there. I think they just gasket matched it. Couldnt' be any harder than porting your own heads and i know you've done that before.

Then save up for the 58 later on.

 

I believe the AS&M 58mm Tb flows approx. 1050CFM, the stockers is supposed to be around 750 CFM, and the 52-54mm should be somewhere in between around 850-950CFM.

 

If I remember correctly, the 52mm flows about 750cfm.

 

Anybody know a formula, or even better a website where I can punch in the needed information and get the airflow requirements for my combo?

 

www.slowgt.com has a racer's math section...i think it should have what your looking for.

 

Get a 58MM and open the intake up to match it.
The 58 may not help but it WON'T hurt your hp.
I have run 2-1060CFM 4 hole air valves on a 408 Ford and it just kept getting faster. I have also done a 1050 Dominator on a 355 SBC,with NO problem.
Your stock mass air will work. The way it is,is if the air is not available for the engine to use it won't make max power. Your engine may not max the 58 but the air is available. A 52 will probably max out and limit your HP.

Your engine will probably need 900CFM@7000RPM's (if it's a 383) and a 58 flows 1000CFM.

A LS6 MAF flows 11-1200CFM (85MM) and can be made to work with your computer,but it will need a dyno tune.

 

The engine is a 355, and I plan on twisting it up pretty high, but still will have to work around the stock PCM rev limitations (7200).

 

By my calculations, a 52mm throttle body will see ~290 feet/sec at 7200 rpm. By the same token a 58mm will lower that velocity to ~240 feet/sec.

Anything beyond ~240 feet/sec and you are going to see a power loss proportional to inlet velocity. For your build I'm putting the 58mm on there.

-Mindgame