I have searched around and found nothing that has been posted that i saw.

My delima is that i was planning on doing a 355 and now have steped to a 383 and already have a brand new 52mm TB wait for install, Would there be a significant power increase to step up to a 58mm. With my set up i should go around 400-420 rwhp with an auto and dont plan on spinning more that 6600rpm. My issue right now is im about out of money and buying another tb wasnt in my plans but i think i can sale it now being brand new better than used and maybe only loose $100. But if it would be about the same i would go ahead and use the 52mm. Any help would be appriciated.

 

probably 5-7 horse.

If I were you I would sell your 52 on the classifieds and use that $ either for a new BBK $310 shipped, or any other used 58mm TB.

 

I would do the same thing also.....

 

I'm not sure there would be a huge horsepower gain but I had to decide the same thing when I bought mine. I have a lot of head work done so I wanted to get as much air flowing in as possible. I went with the 58 mm but I then had to open up the holes on the intake to match the size of the TB blades. Otherwise it would kind of defeat the purpose of getting the bigger TB. I'm not sure what size the intake holes are exactly so you might be able to use a 52 mm without bothering with the intake. Good luck with your decision.

 

they are 52 mm so you can upgrade to the 52 mm with no problems. although if you have a dremel you can put a slight chamfer on the TB ports to smooth the air flow, and you'll need to find a matched air foil or grind a 48 mm one down if you go with one.

 

I bought a 52mm used tbody also before I decided to make the eng. a 383. I think there would be a slight diff. , but prolly nothing you'll really feel. I would try to sell it, but I def. wouldnt take a $100 hit. you should be able to sell it for closer to $50 off new w/o a problem. but if your pressed for time, as in your eng. is done and ready to go, maybe you should just sell it for whatever.

 

Do 58mm TB make a difference on a stock motor??? I WILL be getting h/c in about a year though....

If I got a 58mm TB what should I upgrade as well? Do I need a tune?

 

58s dont do anything really for a stock engine. You might even find the car bogging at WOT until a tune. I would do a 52 in a stock application, and the 58 on a stoker. The stroker will be looking for more air on each stroke of the engine.

 

Yea the intake has been opened for a 58mm. I think i will go that route. If it is 5-7 horse i will do it.

Thanks guys

cal

 

then what would u guys reccomend for a 396 with h/c? a monoblade? how much u think those go for used?
thanks

 

FWIW I have a 52mm on my 383, and it pulls up to 3" of vacuum at WOT. I am currently in the process of swapping it out for a monoblade, and I will post the results when I get them. I would likely be fine with a 58mm, but decided to go with the monoblade since I didn't want to spend $450+ on a throttle body twice. If you can't afford the monoblade right now, still port the intake for it if the intake is still off of the car. It is much easier to keep clean and you dont have to worry about getting metal shavings into the combustion chamber. The larger holes behind the t/b won't hurt much if at all with respect to velocity, so it will just make it easier for the future if you decide to upgrade.