Kubs

I am thinking of having the plenum on my '90 ported by CorvettePlenum but I dont want any downtime. If i find a plenum from an earlier model or even a camaro, how hard is it to make it work with my SD setup? I notice there is something that bolts to the pass side rear of the plenum on mine, and no hole for its mount on earlier ones, what do I have to do in the way of sensors?

GREGGPENN

You'd have to drill/tap any missing holes/mounts/nipples or you could just find a plenum for your year.

FWIW, I actually have a speed density plenum that's already ported Corvette Plenum style (matches the one I've posted for my motor). I ported it. It's not polished but it actually has an extra hole (drilled/tapped) for extra vacuum accessory or FI equipment. (I know 2 or 3 sources for the nipples is you needed one.)

I can send a pic if you're interested. You'd have to get another screw in nipple and/or plug the extra hole with a plug from the hardware store.

redrose

that 'something' IS the maP sensor...to use an earlier maF plenum, use a plastic tee in either of the vacuum hoses leaving the pass side rear of the maF plenum and a piece of vacuum hose to the inlet nipple on the underside of your existing maP sensor...locate the 'hosed' maP sensor anywhere, but 'just hangin' where the hose carries the weight ain't good, inside the cockpit is best for sensor response (more stable air reference indoors) and longevity (lower temp) if you wanna use a couple extra feet of hose and extend wires for the maP sensor.

stiff nylon tubing with a couple inches of rubber hose at each end is good to avoid hose collapse under high vac conditions or other stuff pressing on the hose.

Kubs

How much? You can send pics to Kubs_63 at yahoo.com Im asctually just looking for a cheap replacement while Mike has my plenum. I ported mine by hand too but he is going to clean it up for me and port my SLP runners to match. I was just going to throw a stock setup on to keep it running in the meantime.

So your saying the MAP sensor is the only difference that can be solved with a tee and extra vacuum line? That sounds easy enough.

redrose

b-b-b-b that's all folks....BTDT...even a cave woman could do it.

GREGGPENN

Seems to me there's another difference. One guy (with a black Chrysler as his avatar) found this out. I'm thinking the CSI caused a leak because the holes didn't line up. He pulled it and sold in C4Parts.

Edit: Look at page 5 of this PDF document. Notice the difference in the chambers cast in the underside of the A plenum vs the B/C plenums. I wonder if there is a 5th (smaller) hole on both sides of the plenum. One of which wouldn't seal if you got an earlier plenum. (Plus theres the issue of the hole between the TB ports on the early vs late plenums.)

I thought you were just getting a plenum ported and could use (buy) mine directly w/o having downtime (since it's already ported). Misunderstood you. Haven't thought about price yet, though it will be more than the elcheapo replacement you're looking for. (Can't let the porting go for free!) Sounds like we should skip it.

qws

I would assume that the tune would have to change as well?
MAF to MAP?

My ebl supports multiport only if its a speed density setup. It doesn't support MAF so I'm just making the assumption that that would have to change as well.

GREGGPENN

I think he has a "line" on a cheap 87 plenum and wants to know if he can temporarily use it while his 90 plenum is being ported. No change to programming is taking place (that I know of, e.g., from SD to MAF).

CooterCatchinVette

Not trying to hijack. Random question. Can runners from an 89 vette be used in place of my stock 90 runners?

Kubs

Correct, everything will still stay MAP just need a temp. replacement.

I would get your nice plenum if I could send you my runners to match the ports.... In your engine thread your runners looked very well done!

GREGGPENN

Yes

GREGGPENN

Thanks for the compliment. I'm not sure I'd want to port a set of SLPs like that again. I'd have to think about that. (OTOH, just doing the top -- like CP looks to do might not be so bad.)

Kubs

I just got the chance to look at the PDF. It looks like the '90 and up does only have one passage under the plenum. I think that could be solved with a pipe plug, or some type of cap in the one that is exposed, that would not interfere with the tube mounting.

GREGGPENN

Agreed. Just don't do anything (plug-wise) that could get sucked into the motor!

The only other issue is the IAC thing....hole between the plenum's TB ports. I can't remember if I've read how air flows thru each of those configs.

May not be an issue though.

Kubs

Since it is blocked on the newer plenums, and a different throttle body is used (according to the PDF) perhaps the IAC does not depend on if there is that opening or not? Something to look into..