Thread: Intake manifold options

bellmouths inside? whats the length and diameter of your runners?any more photo's?

No bellmouths, and runners measured just under 7 inches.....I'll post more pics later

Love to see how this perform. What size plenum?

I've read through the majority of this and wanted to touch on a few points. In my opinion the xcessive runs out of breath just a little too early on the VE. Usually around 7800 rpms and you may as well shift because you're wasting time. You may as well go back to DET. I know for a fact that on the VE runners if you add between 1"-2.5" you can fine tune your powerband to exactly where you want it. Center fed manifolds seem to keep egt's much closer on every cylinder from what I've experienced although feeding the TB can cause issues. I Run an oval TB with dual plates on it with the reasoning that not only does it feed the cylinders more evenly, I have a monster ass 4.5" diameter 90* bend before it and it narrows it in the direction of the airflow (if that makes sense). The inside and outside of the bend match up to the long sides of the oval.

V stacks seem to work really well, although I haven't compared them side by side with one that doesn't have them.









Extremely important that the inside is prettier than the outside.



These runners put you at around 7900 right with the excessive.



And these replace excessives. This was a duplicate, I would have liked to have seen him go just a little shorter.



These runners were good to 8250 rpms.

I hope this helps some of you clear up some questions you may have.

I'm guessing your referring to the short xcessive plenum on the standard runners,not the n1 type,although I see the n1spacer in there? A few pr guys might disagree with your findings,porting being accounted for?

Yes I'm referring to the non n1 runners. That center fed plenum made power to 8200. Non-tuned vs. tuned with N1 cams. Runners were around 6.5" iirc.



A similar side fed with 7" runners made power to 7800. Chart overlaid on factory intake.



These are all hand port jobs on the runners. Basically just making the center ports match the outside ports in size and matching the plenum to the runners. No crazy porting, and both on factory port heads. Here's an example of the porting before it's smoothed out. Keeping the stacks round on this one instead of ovaling them out.



Proof is in the pudding. I don't mind sharing what I find, just hard to find the time to do so these days.

what headers did those dynoed charts use? Stock intake manifold still peak out just after 8k on a good header and n1 cammed motor.

The center fed was on an ASP. The side fed was on a JMR with shortened primaries and reduced choke.

So 8" runners should yield around a 8500 RPM peak? I am planning on having a set of lower runners made and am debating on using the aluminum velocity stacks or just the plastic kits from excessive. I will also need to have some pie cuts added to the tubes to keep if off the firewall some so i can retain the heater core. I will be bringing my car home at the end of February and will start mocking things up. I was debating on just leaving them on the stock lowers but i might as well go for the new runners now since i need to re-tune anyway.

Shorter runner should = higher peak power.