What gains would I get by replacing my 48mm stock throtle body with a 58mm? And which brands would you guys reconmend?

 

Any other mods to your car? With a 58mm you have to bore the intake openings to match the TB gasket. All depends on the other mods on what youlll gain from it.
Id go with bbk if you end up doing it.

 

what gains do u think id get?? 5 hp or so?

 

With your mods, I would say AT LEAST 8-10 RWHP

That stock throttle body has gotta be chocking you, especially with already ported intake, heads,etc..

 

That's probably close. I had a similar setup in mine and saw a proven 10 RWHP on the dyno going from a 48 to 52. There was a loss of 1 ft. lb. of torque. I'm not sure if the extra air from the 58 would help you, and it may hurt low end slightly. BBK by the way on tb choice.

 

I did'nt do a before an after dyno, but once I installed the 52mm BBK throttle body, I could tell that it had alot more throttle response to it.

 

If you have a bolt-on or stock motor, you will see very little gains with a bigger throttle body. If you do decide to do it, having your stock throttle body ported is the cheaper alternative. Otherwise, you could buy an aftermarket one from Holley, BBK, ASM, and even Summit makes one.

 

UI got the 58 mm tb and port mtched intake. I love it. Noticible power increase and that sucking sound that the intake makes is awsome. Sounds superchaged a little. IMO... get the tb and intake instead of just one. You wont regret it

 

my intake was ported but not the TB holes I was thinking just do a 52MM since the holes are already that size would I have to get it retuned or is it not that much of a diff the computer should adjust?

 

I think you can't go overboard even at 58mm because the new 'stangs are little bitty 281 cube motors and they have 55mm as stock. The hot rodders are increasing them to 62mm as far as I know. Are their cams and heads that superior that they need so much more volume than our Z28's? I don't think so.

 

ya well i dont want to put a 58 due to not being ported for it so its gonna get resistance then... thats the only reason i guess it would make some shelf and hurt it more then u know help it but 48 > 52 should be a good increase i think a good 4-8 maybe 10 hp?