So I'm going to EFI, will be running 540cid F1c Procharger and a 370ish intake cfm heads, boost will be low 6 to no more than 10lbs. I'm driving myself crazy over the intake I've decided to use the SPX as I have it already, it's a 4150 flange, but with the larger Blowers and big cid 4500 flange desired, no real big deal as I can open the plenum exposing the runner walls which would then be knifedged etc . Or would leaving it somewhat 4150 size maybe open it 1/4in around and do the same to the 4500/4150 adapter and put a "neck" in the plenum with the larger 4500 opening on top blending down into a slightly larger 4150 opening of the intake? Would that promote velocity? In my mind it would, or would it be a restriction?
Keep in mind if was ran 4150 side up, the shelf would be gone because the plenum would machined open,
I assume your running an elbow and forward facing TB? Or is this a blow thru? I am building the 4500 flange SPX/Wilson Elbow/105MM TB right now, and it's a whole bunch of machining and handwork. This 555 will run 15-20 psi, and has nearly 400 cfm cylinder heads on it. JW
Knife edging can be bad for runner distribution/airflow reasons. It can force the air to sheer and change direction with the pulses and direction changes in a manifold, whereas a bullnosed front doesn't fall victim to the 'vena contracta' effect. I think people with the right equipment, etc. may still do that due to trying to carve out more CSA than practical in the casting.
Set it up to be a Venturi shaped as best you can. a tad smaller in overall volume can more than be over come with a mere 1.5 psi more in boost! The Venturi will give much better fuel distribution! The radius leading ino the top of each runner should be as close as you can get it to the radius of the top of a runner left to right wise, or even softer.
Ethan, With a Tomahawk build like yours I am surprised you don't just sell your 4150 SPX and get a new 4500 manifold. In the grand scheme of an EFI S/C Tomahawk build the difference is not worth worring about. Just food for thought. Good luck with your build!!! Jim
I guess I'm more after distribution quality , HP will be there in abundance, no matter how i go about it, just want to keep all the holes burning good, Its one of those things you won't know till you try I guess,...just don't want it to be a very expensive lesson ha
Might be tough to do on the bench before any testing. I'm thinking you'll want to spend some time with your head and intake on a flow bench, maybe shoot some ink down the manifold. Creep up on your tune on the dyno, using a temp gun aimed at the exhaust port or temp probes. I know, obvious...
