Ok I've done a bout an hour of searching and haven't really found my answer..

Basically I'll be running a stockish 318ci engine (gapped moly rings, 228@50 .480 hyd cam) 75mm turbo around 12psi, chasing 500rwhp

I've decided to go efi and ended up scoring a cast edelbrock throttle elbow (part#39493) ridiculously cheap.. But it's to suit a 95mm throttle. I've done some mucking around to it and I'm able to fit a 90mm pretty easily.

Will this have an effect on drive ability or tuning? I know it's on the large side but I like making do with parts I have.

I'm planning on an alloy headed 400+ci motor in the future so not having to change them would be a bonus

Thoughts?.... Or should I make up my own elbow and go a 75mm

 

As it's a part of the plenum, a smaller than intended throttle body shouldn't be a big issue as long as the throttle body itself is large enough (and 90 mm sounds like plenty for what you're doing). A too-big throttle body is a bigger problem; if the intake necks down, you don't get the flow the larger throttle body allows.

 

If you have a 90mm and you are planning on building a 400+ ci engine later, go with the 90mm. Tuning should be reasonable. My 331 with a 90mm is just as streetable as my 351 with a 75mm TB.

 

Thanks guys.. Just wasn't sure if the 90mm was going to be "too much" for the 318 to be easily tuned and drivable in the bottom end.

I have one on the way

 

Sorry to hijack but my FAST 102 split and we are putting a 78 MM stock LS1 intake on it. The inlet pipe from the IC is only 2.5 inches. I am assuming I shouldn't really see a problem dropping from the 105mm to the 78 mm since the inlet pipe is even smaller yet. Engine is 408 Ci, any thoughts?

 

That elbow accepts standard LS1 or ford pattern throttle bodies. I'm sure you could find a stock LS1,LM7,LQ4, or 5.0L throttle body for next to nothing. I tried using my fuel injection setup on my 305 one time the built motor was broke and it didn't really work. I'm not sure if it was because of the 105mm throttle body or more because of the 95lb injectors. A plus with boosted setups is that the throttle body only needs to be big enough for the power the engine makes without boost.