Hey guys just pulled the motor and noticed that the stock TB holes and the holes on the plenum are the same size. If I go with thee bigger TB will I have to enlarge those holes. If not I dont see the purpose. Dunno I'm kinda buzzin but I had to ask.

thanks

 

The stock intake is good up to 52mm. Anything larger, the intake manifold will have to be ported.

 

Do I need a 58mm for a 383?????

 

ttt

 

I'd say up to about 500HP, a 52mm should be fine. I have extensive engine dyno testing on a 381 with a 58mm TB, and at about 500HP the TB was flowing all the air the engine could handle at only 77% open. That corresponds to about the open area of a 52mm TB. GM includes a 48mm TB on the 502ci/502HP RamJet big block crate engine. A 58mm isn't going to hurt though, at least not on a 383 making decent power.