Precisely. 57ChevyThunder turned me on to the Ken-Co sleeve, too. It simply would not fit...and it was a good 1/8" too big. There was no way that the sleeve was going to fit in my new UIM. It'* been almost a year since I did the work so I no longer have my index card with the dimensions that I took. The interesting part about all of it is the the Ken-Co dealer that I bought the sleeve from didn't think it was odd that it didn't fit (I think the name of the dealer was Gallions, up in Maine). They gave me a refund, no questions asked. I got the impression that it was almost protocol for it to not fit in some UIM. :?

it'* 6061 t6.

as for dimensions, they've been changed a little bit since they were first brought out.

something I never noticed before, but just did -

the center of the pipe is actually .3mm smaller than the ends (OD). this little beastie has more engineering behind it than what it appears to... but keep in mind that the tolerances on the print allow for +/- .3mm for those dimensions. wonder if the supplier just made them a constant diameter, instead of reducing it in the center?

anyone that has their old EGR stovepipe out and available, put it on a completely flat surface, and see if the middle touches the surface.

and whether or not it does, if you have access to calipers, measure the OD and ID at the ends, and the OD in the middle.

if what i'm thinkin is right, this might be a nasty case of lazy supplier (but don't quote me on that, it'* a suspicion, not fact)...

I'll look for my old one today to measure it. My old one was not perfectly round - it was squashed a little along its length, which made for a nice tight fit in the LIM. I do not recall any thinning in the middle, but I will check when I locate the little bugger.

and Vital, was your sleeve 1/8" too big in diameter?

From what I recall, it was about 1/8" too big.

And as for my old stovepipe, I had to really mangle it to get it out. In retrospect, I wish I hadn't mangled it so badly because it caused a lot of extra work to restore the shape of it so that we could reuse it. It was definitely not a slip-in fit. Does that help support your case, Matt?

i don't really know. they've never released (and don't plan on releasing) the print for the composite upper, so I don't know what type of a fit it'* supposed to have. From looking at what I do have available, the egr stovepipe should get very slightly (Again, we're talking less than half a milimeter) smaller in the middle than at the tops.

OK, now I'm confused.

After reading the dimensions, etc. posted above, a question springs to mind.

Why bother with machining at all? Any metals broker has .750 stainless tubing available. It'* used in the food preparation industry.

If the port in the block is .750, and the passage in the UIM is .755, as mine is, why screw around with machining? All that would be needed is a length of stainless turbing of the appropriate length.

Somebody help me out here? :?

Well, the reason you want to machine it, is to create some distance between the hot EGR stovepipe and the ID of the plastic plenum to eliminate deterioration of the plastic from exposure to the hot pipe. The idea is that the air space and the sleeve keep the temperature of the plastic from getting high enough to deteriorate. Whether or not it works in the long run....who knows? GM justs puts in new manifolds and figures you are good for another 80-100,000, but you have to admit, that is a pretty shabby approach to addressing the problem. This is why we want an aluminum upper. I may pursue a different approach to get an aluminum upper by buying an L67!

OK, now I'm thoroughly confused yet again.

If the factory part uses the plastic of the UIM to transport exhaust gas to the plenum, it just makes sense that epoxying in a stainless sleeve is going to be more long-lived.

Could somebody please post a pic of the stock EGR part, or in the alternative, give me the part number so I can order one and visualize what we're talking about here.

Bill, you pic above has three pieces in it, and I thought the Kenco part was 2 piece. Whcih one doesn't belong? Thanx.

I'm sorry I didn't explain better earlier. The piece on the left is the stock EGR pipe, basically just a 3/4" O.D. piece of stainless steel tubing in my case. It is 1.420 inches long and has a wall thickness of about .035. It press fits down a quarter of an inch against the shoulder shown into the LIM. When the gasket and UIM are installed, you can see the top of the stock EGR pipe stick up about a 1/4" or so into the air stream.

I can't find my stock EGR pipe to check to see if it is a little narrower in the middle. It may be, but I don't remember that when I was working with it.

The parts on the right in the picture above are the new pipe and sleeve my buddy made. I'll see if I have more pix.

This is my reduced diameter pipe shown in place with the sleeve installed in the plenum. You can see the .086" gap on one side all the way down to the shoulder of the pipe. The new pipe is centered although it doesn't appear to be in the picture. The height into the air stream is the same on the new pipe as the original. My sleeve did not quite make it to the top of the plastic plenum. I should have made my sleeve so that at least a part of it stuck up into the air stream too. I think that would have helped a lot to remove heat from the plastic. Heck, maybe I'll just take it apart and make a new sleeve for a new plenum and be good for 200,000 miles! My plenum was warped where the TB seals anyway.