I'm pretty much done building a 355 and was wondering if I really need to get a bigger throttle body. Everyone seems to jump the gun and get a 58mm with simple bolt ons. I've been reading that the 502 came with the 48mm and ran just fine.
This build of mine has Le2 heads, 232/240 cam, ported intake and all the bolts ons.
I mean really, can the 48s be choking it? I don't wanna cheap out this late in the build but I've been debating this for awhile. Thanks.

 

Unless you dyno in the 500 hp range, no.

 

I'm running a bone stock 48mm TB with a bone stock intake. 414RWHP.

LE2 heads, 355CID, 230/238 Lunati cam, my build is slightly less than yours.

The larger TB will increase throttle response and maybe even add a couple more horsepower, but the money can be put else where, like in gears and suspension, or a C5 brake conversion.

I'd say, if everything else is done and you are still looking for that couple extra here and there, then go for it. But personally, I'm sticking with my stocker until my rear, gears, chassis, brakes, interior, and paint and body is all done first.

 

That's what I've been thinking

 

On another note, I have a BBK 58MM TB for sale that I bought this February. Used it on my AI Heads Cam LT for about 2 months before I parted it. Less than 2k miles on it. Let me know if you want one we can work something out since they are extremely expensive brand new

 

I actually found a 58mm hidden in my garage today but I'm still debating to install it or get rid of it

 

My 355 build is similar to yours. 355 le2s with a 231/239 cam. Lloyd said that since I already have one of his ported intakes that I should run a 58mm tb. I already have a 58 and a 52 bbk in the garage ready to go on. I guess I'll see which one the motor runs better with.

 

I bet it runs great with the 48 but the most you would need would be a 52mm. I would think the 58 would be overkill. I'm jealous I want LE heads and cam!

 

ale76...

if you had your intake machined out to use a 58 than you could install yours since you have it. your PCM will need to be tuned for it, especially if you have a A4 car. Typically aftermarket TB's require some "adjustments" to get them to idle right, especially with cams. This is done by drilling a hole for the IAC passage but don't do that blindly, use a scan tool first to see WTF your IAC counts are.

IMHO a stock 48 bored to 52 is more "plug & play SHOULD your build require a larger TB...and is cheaper than buying a aftermarket one

 

Thanks for the advice