Im looking for a new trottlebody. Should i get the 52mm or 58mm. The only mods on my car is hedders and 3 inch exhaust and no cat.

 

If those are your only mods, on a 305 even. THen I would not bother putting either on your car until you get the complete internals to breath and work with such a mod. Try a search on this topic and see what you come up with. Alot of people ask this same question and get the same results...don't bother! But to each ther own, but I think it would be a waste of money for you at this time. You need to open up the intake itself. the heads, some bigger injectors, higher fuel pressure. I would cahse after some of these mods before atttempting to up the size of the throttle body. HTH

 

i second that

i've seen test where they put a 58mm TB on a stock 350 and they lost about .3 in the 1/4

 

GM has a 502 cui ram jet engine 500hp 500 torque and has 48 mm TB........................58 mm is def. going to be a overkill! Do a seach and you will find alot of info.........

/N.

 

This is a heated topic just like Speed Density -vs- MAF that some people will die for

It seems though, that the general concensus is, that unless you are running a stout 383 or more, a 52mm is more then enough.

And if it makes a difference, I ran a 13.5@ 103 on stock runners and stock TB.

 

Thanks guys. Well i think im going to start whit a bigger fuel preasure regulator and these new runners.

 

That will all work much better, and cost close to the same. Also I would look into have a chip made up or get into makeing your own even.

 

i went with the 52mm on my almost stock engine (the old one's shaft was loose giving me a high idle 1,500RPM) so I just got a performance part as a replacement and 58mm is definitly overkill, have a buddy who put that on ported plenum and all and the thing would bog like it lacked adequate fuel.

 

i say, if ur gunna build up a engine, and keep the TPI set up... get the 52

 

GM ships the 500hp Ram Jet 502 with a 48mm throttlebody. Food for thought.

 

I'm not trying to argue, so don't take this the wrong way, but what your saying is overkill. Like mentioned the 502 crate engines only come with a 48mm TB. Unless he is trying to build a engine with over 600 hp right now he would be wasting not only his money, but his fuel economy too. It isn't going to help him any right now, if anything it will slow the car down some. Just my 2 cents, but it worth it.