I didn't see any examples of this here, so I'm wondering if anybody has done something similar. I was grinding down the walls just inside the plenum entrance, just like everybody does. Then I started looking at the casting and realized that the big trenches just inside the openings aren't helping flow at all. So I smoothed it all in from the throttle body holes to the little walls with JB Weld. Here's a picture of it almost completed:

 

I think it's been done once or twice, along with the runners:

 

Cool. But what do you fill on the runners?

 

What exactly did you 'fill in' on the plenum? Typically you knock down the walls and then smooth everything out. I've never 'filled' anything on any of the plenums I've done. Well except for un-neede holes for odd year part swaps etc.

And watch out for that old guy, He's going to try and slip you some anti-seize before you know it!

 

Check out my website for pics on how I do them.

Corvetteplenum.com

 

dude you have more cutting to do

use a carbite bit and wd-40 anything else is a waste of time.

 

OK, right behind the intake holes the plenum drops away. The side walls come in behind this. Even if you grind the side walls back, I don't think you can ever get them all the way out of the way without grinding clear through the casting. So instead of taking the EGR walls all the way down to the floor, I brought them down to the shape of the intake holes. Then I filled in the gap that goes about 180 degrees around each intake hole (just on the back side of the front face). This is the gap between the front face and what's left of the EGR walls and between the front face and where the side walls come in. This way the intake hole shape extends back into the plenum like 1.5" and then everything opens up.

The darker color of the JB Weld is obvious in my picture

I don't think I need to bother siamesing anything since I have a stock throttle body and stock runners.

 

Dude, Did you check my website? You can blend the floor and sides perfectly without danger of going through the side. Just take your time and go slow.-Mike

 

Those plenums look great. I will do some more cutting. I still think that along the sides it could benefit from some filling for a smooth transition.

Why are the EGR holes shrouded anyway?

 

Who needs EGR?

 

Excellent question. The EGR is not functional at larger throttle openings. At lower throttle openings there seems to be plenty of vacuum to get the EGR gasses to the runners instead of reversing (I'm not sure what Rochester's philosophy was on this). I just left my EGR openings in the floor, unshrouded. No known problems in about 7 years.

 

Holy crap, that's all filler? Yea, you need to cut more. I didn't realize that. As Mike andVader said, you can cut the walls all the way down and make all the transitions nice. I've done dozens and dozens that way and never had issues.