Trying to get some parts together for buildup. How much throttle body is needed for 400+ rwhp? I was thinking of a AS&M 54MM But a 58 is the same price and getting the intake ported will be a part of the build up. Should I go for the 58 or is in unnecassary?

later

 

ttt

 

it's been posted here many times that a stock TB can support 400 hp. 52 mm flows about 750 cfm, unless you have a really good stroker or forced induction you probably don't need to go bigger than 52.

 

Since you're going for 400+ at the wheel, I'd go for the 58.

 

I believe the 52mm throttle body is plenty big enough for your goal.

 

The 58mm has no disadvantage other then moving air slower accross itself, that's not important on a fuel injected motor.
I say go for the 58mm it's less restrictive and the mixture velocity wont change where it counts and that's on the intake runners.

 

I had a 52mm on my 383, and I was pulling up to 3" of vacuum during dyno pulls. I switched to a monoblade and it was reduced to about 0.5" of vacuum. At the time, it was putting about 408 to the wheels through a 10 bolt (~465 fly hp). I would go atleast with the twin bore 58mm since it doesn't cost any more. It definitely wont hurt you.

 

I put a 52 BBk on my car and didn't notice much change in anything but did have wrong factory 48 gasket on there . I then got a 58BBk with proper gasket and didn't port out intake right now. The tb still seems to work fine ,throttle response is fine didn't notice much if any changes. I figure can port out intake later on when add ,heads,cam /headers or get a stroker but the 52 and 58 were same price so why not get the bigger one I figure.Also smart guys like Lloyd Eliot recommend the 52 on his milder combo and 58 on his wilder combo so figure he knows his stuff and has done lots of dyno tests.

All I can say is my car is certainly not running slower with the 58 on there and may be a bit quicker. Of course its actiing like a 52 right now since the intake is already set up for 52mm.