Custom Upper Plenum idea


Active Member
Feb 4, 2004

Well the Rivera is short on hood clearance with the stock intake setup and I'm looking for ways to reduce the height. After going back and reading Bruce's Plenum Volume experiments I'm considering doing something to try to smooth out the air and increase the plenum volume in addition to lowering the height of the upper plenum.

Bare with my MS Paint drawings.

Basically its a 4in tall box with a 3.5in pipe cut open in the back to form a deflector baffle. The front is an LT1 throttlebody to keep the GM compatable sensor stuff and for it's lower profile.

I've also thought of another idea but not drawn it up. Still using an LT1 TB it has 2 funnels running off of the back of the throttle bores that are notched down the outsides. The outside plenum is another 4x7x7 box with rounded outer walls to direct air evenly into the hole of the stock or a Champion lower intake.

So while rocking the baby to sleep lastnight I realized that making the flange a -10deg would only cause problems so design revision 1, the flange is now flat and the forward face of the plenum now has the 10deg tilt to bring it parallel to the hood line. Looking at the way the throttle cable mounts I've also revised the overall width so it's now the same width as the TB which will lessen the thickness of the mounting plate for the TB. This however will length the plenum (shooting for 200cid) so with the coilpack behind it I'll have to push the whole assembly forward, not a bad thing though.

I also toyed around with order of operations to bend this up without getting in the way and think I've got that part down