Why in the world are you guys reaming the upper? Aren't you just making the wall thinner? That'* just asking for trouble IMHO, even with a sleeve. Especially since it is not necessary unless I missed something in this thread. I did my upper last summer and as I recall I made the pipe with a .500 I.D. / .050 wall thickness / .050 air gap and I think that left about .025 for sleeve wall thickness or there abouts. I did not stick the pipe into the intake air stream but I like that idea. Now why didn't I think of that.

To Bill, and Ranger: Yes, a person could probably "get by" without reaming and sleeving the UIM, as long as you are using a smaller EGR tube with a decent air gap. The key words being, "get by."

BUT, as for me, in my old mechanical mind, sleeving the upper is "BONUS POINTS." As I think I have already stated in one of these threads (-may not have been this one?) my 2002, which has the "somewhat smaller tube" (.625) from the factory, and still uses the .750 hole through the plastic, the plastic did not show any signs of deteriorization (softening, or crystalizing) at 44k miles. So, does this mean that I could have simply left things alone ?? -and "got by" ? -Yup, probably. But I can tell you for sure I feel much better on my 2002 by having installed the sleeve anyway. And on the '99 (which had a totally toasted UIM) when I used Ken Sprag'* kit with the .500 tube, and the sleeve in the plastic. -fact is, I'd guess that I'd bet anything that the '99 WILL NEVER FAIL again. (-as related to the EGR, that is. ) I'm thinging that maybe the lower gaskets will fail again, maybe some 100k miles further down the road. -but that is a different topic.

At this stage, we are probably trying to speculate on some pretty "fine lines" as just what is necessary to "get by." I guess one way you can look at it is, Apparently GM has gambled on "getting by" by using their new .625 tube, and just leaving the plastic hole. -it gives them a .125" air gap, and that tells me that they feel this is adequate.

I can tell you for sure, that in my opinion, those people who are taking the extra time to give themselves even better insurance, are doing a good thing, and should have much greater peace of mind as well. Bob should be given a lot of credit for going the extra mile, and creating a much longer lasting, more reliable product in the end.

And as far as penetrating into a coolant passage, and epoxying in the sleeve, I see ABSOLUTELY no risk there at all. In fact, due to the sleeve alone, it should outlast the plastic by a huge ratio.

Thinking about "getting by," I'd bet that a person could simply ream out the UIM to at least 7/8", (maybe all the way up an even 1 inch) and leave the stock .750 tube in the LIM.

But would I do it myself,,,,, hmmmm,, I don't know. I sure do like the combination of sleeved upper, and smaller EGR tube.

Thanks for weighing in, Ranger, we appreciate your input. This discussion is a little difficult to follow because it is taking place simultaneously in two threads (not the best way to keep things clear). The discussion originated here: http://www.bonnevilleclub.com/forum/...653&highlight=

To answer your question, the upper is reamed only when the material removed will be replaced with material that is far more resistant to heat and pressure than the original plastic. There is no question that stainless steel is better than plastic for these applications. We are, however, presuming that the JB weld to the sleeve will be as strong and heat-resistant as the original plastic. JB weld is rated to 600 degrees F, I believe.

I reamed my upper to remove the plastic which had deteriorated to mostly carbon as a result of exposure to heat, and to provide a centered, accurate bore for the insertion of a sleeve. By the way, unless you look VERY CAREFULLY, at just the right angle with a bright light, you may not detect this deterioration. It is really insidious. If you take a penknife and attempt to gently scrape the carbon layer from the I.D. of the plastic in a manifold that has seen 100,00 miles of service, you will see what I mean.

Another important reason for reaming is to insure that you get a good bond between the JB weld, undamaged plastic and the sleeve. Reaming accurately cuts away the damage or carbon buildup, and exposes clean plastic to provide the strongest possible bond.

As we share ideas on the best approach to this problem, I am concerned about significantly changing dimensions from what GM does. In our discussions here, we have yet to hear from someone who clearly understands the relative importance of heat transfer by radiation, conduction, and convection in this trouble-prone area - not to mention the effect of changing the EGR flow rate and velocity. But you can bet that GM has done these analyses. For that reason, I am hesitant about reducing the pipe much beyond GM'* revised OD of .625 Likewise, I am concerned about increasing the final ID of the upper because of potential problems with centering and how the gasket seal might be adversely affected. I don't know if it is more important to remove heat from the sleeve or from the pipe. This would dictate which protrudes farther into the air stream. I'm not saying your approach isn't better here, Bob, but I would probably be more conservative and leave the reduced diameter pipe at 1.420 and keep the top of the sleeve somewhere less than that.

The EGR bore in my OEM plenum probably started out at .750. I reamed it to .829 (which still left a little damaged plastic) and JB welded in a stainless sleeve with a .035 wall. This resulted in a final ID of .760, only ten thousandths bigger than original, or .005 on each side. But my gasket seal was probably offset by at least .005, and probably more, because if is not likely that my hand reaming was perfectly concentric to the original bore. So, the wider you go, the more likely you are to run into problems with sealing. It won't do us much good to strengthen one area against leaking coolant if, at the same time, we are weakening another.

[edit: I agree with you, Ranger, that it would be best to keep the plastic thick if possible. The problem comes in trying to find readily available sleeve material. (That'* why Bob went to 7/8".) If 13/16" OD .025 wall were readily available, that would be perfect. The bore wouldn't change much; we wouldn't need to go too close to the water, and we would still get a decent air gap. You get all that with a KenCo kit. What we have been trying to do is to find a cheaper way than KenCo, that works as well. For most of us without a lathe, it turns out that it is not that easy. Notwithstanding GM'* recent revisions, until someone can demonstrate a better fix, I agree with Harry and Ken Spragg that the combination of a sleeve and reduced diameter tube is the best approach. But I still hold out some hope (like Bob) that we can find a cheaper way.]

Now, the neat part about all this is, by my count, we have at least 5 test vehicles, each with slightly different repair methods, to evaluate any potential benefits and problems. It is extremely helpful to have several different heads working to solve the same problem. All we have to do is keep in touch and report any problems we run into.

My goal is to find the cheapest, easiest, way for the average Joe to do this fix so he won't have to worry about it any more. Please note, I am not ignoring the importance of the LIM gaskets, just focusing on the upper for now.

Sometimes, pictures are better than words. And in my case, a lot better than my memory. I had thought that we just left a little deteriorated plastic after cutting away .040 material with the ream. Here is what the bore looked like after reaming



Here at 10:00 O'Clock you can see how the heat penetrated in waves




Here at 12:00 O'Clock you see more alteration of the plastic



And, here at 2:00 O'Clock you see the deepest damage not removed by reaming

Upon initial inspection, the bore in this upper looked good. It appeared to have only a light layer of carbon on an undamaged surface. I would not be surprised if the degraded plastic runs all the way through to the coolant bore. Sure makes me glad it has a sleeve.

Hey Bill, EXCELLENT thoughts and photos !! -and like you, I'm a little nervous about departing too far from the factory dimensions.

I've always kind of wondered about the 1/2" tube in the Ken-Co kit. I guess all that I can say about that is, so far it has performed flawlessly in our '99

I'm ordering parts today to do my Brother'* '98 LaSabre. -so we will "sort of" have a sixth test vehicle. -but, more like another one using Ken'* kit. Also, I've heard some folks say that they have never heard of this failure on a Buick 3800 series II. I've always been a little curious about that. I sure wonder what I'll find there. -the car is approaching 100k miles.

Anyway, it will probably be more like 2 weeks before I tear into this one, what with the Easter weekend coming up next. You can be that I'll report in on what I find.

Hey, Everybody Have a Great Day, in spite of ourselves,,,,
Harry

I'm surprised that people claim they've never seen this happen in a "Buick L36". Afterall, the 3800 is a Buick engine...

GM was using the Delphi until the series III came out.
Don't think there is any associasion with dorman.
I understood the change from Rochester to Delphi took place around 01 but I am not sure. I saved my original Rochester as it is a good candidate for the sleeve.
Although by now the Junk yards should be loaded with Delphi UIM'*.
Some of the guys have 99'* with Delphi'* and the only way to tell if they were replacements is by the date code on top of the UIM.

My car had a Delphi UIM stamped 99 and also had a revised lower intake with the smaller diameter EGR tube. Makes me wonder if late production 1999 models had the improvements made then. My lower intake gaskets were junk however with 85,000 miles. I wonder what production date my car has? I will have to check this afternoon.

Just ordered another Ken-Co kit.

DANG IT That $80 sure bites, doesn't it !!!

Whomever among you wishes to sell "their kits" PLEASE LET US ALL KNOW.

You should have plenty of customers

My Brother is a very nervous person by his nature, so he opted for the "ready-made" kit, whatever the price. Otherwise, I'd be for just doing the reaming and sleeving of the upper unit.

Oh Well

Hey Harry, I'm curious about the kind of air gap that you get when you install a KenCo kit. Have I understood correctly that the OD of the pipe is .500? I have ordered some stainless tubing today to try out my idea for fabricating a low-cost reduced diameter pipe by shrinking a 3/4" OD onto a 5/8" OD. If it works OK it will give a .063 gap with no sleeve (same as GM) and a .076 gap when used with a 7/8" sleeve like Bob used. [edit: anyway, if it works, the material cost for the pipe would be about $4.50. And, does anyone know if the '99 -up LIM is bored to 5/8" for a smaller pipe, or if the new pipe has a 3/'4" shoulder?]