if i get a 52 or 58 mm throttle body, is it ok to put it in without porting the plenum right away, or will it run like **** untill the plenum is ported?

 

You won't ever need a bigger throttle body on a 305 TPI, all you'll do is cost yourself throttle response. Spend the money and time porting and siamesing the plenum, porting the base, and install a bigger cam (around 440 to 480 lift and keep it over 220 duration and 112 lsa). You can get this done for the price of a larger TB and it will help you tremendously.

 

no i mean for when i convert to a 350 or 383.

 

even still the 52mm tb is all you need. but as for your question. yes it will help a very small amount, but port the penilum as soon as you can. this site as a tech article on porting it yourself.

 

Yeah, 52mm is good enough. Many people think going to a bigger 58mm throttle body on a 350 or 383 will help more but it will only rob the engine. 58mm throttle bodies are for bigger engines with much more horsepower.

 

oh ok, so 52mm is probably the max on a 383 then?

 

onless you build a stupidly bad azz 383. then yes a 52mmtb is all you will need,and like said before on a lesser setup the 58 will actualy hurt you.