Weird interference issue with plenum installation

[Aurora40]

I've always had this issue where the plenum coolant line, PCV line, and the I/H coolant extension interfere. I never thought much of it until I put two and two together about the slowly disappearing coolant, and the fairly clean nature of the two intake runners next to the coolant passage.

Here is a picture:



I believe this keeps the plenum from really seating properly here. If you feel it, you can not move the PCV line, it is definitely pinched. The last time I removed the plenum, I hammered the PCV line slightly oval to try to fix it, but that didn't really help.

Has anyone seen this before? Any thoughts? I think the coolant nipple on the plenum should be rotated to point more vertical, but I'm not sure how they are retained. Can I just twist it up? Or will that ruin it or cause it to leak? I also thought I could grind that bit of the coolant extension down, but it seems like there should be a less destructive way to fix it.

[QB93Z]

Bob, I just checked two cars, the 1990 and the 1994. In both cases there is 1/16 inch clearance between the coolant tube and the PCV tube.

Interestingly, when I lifted up on the PCV tubing to try to make contact with the coolant tube, I could not get them to touch. The PCV tubing contacted the under side of the injector housing bolt flange preventing contact with the coolant tube.

I wonder if your plenum's mating surface has been machined in the past to make a better seal to the IH's?

I don't know how the coolant tubes are sealed into the plenum, but I have always wondered.

Some guys put a non-metalic spacer between the plenum and the IH's to reduce heat transfer. Maybe that would help your problem.

Jim

[GOLDCYLON]

Originally Posted by QB93Z

I wonder if your plenum's mating surface has been machined in the past to make a better seal to the IH's?

I don't know how the coolant tubes are sealed into the plenum, but I have always wondered.

Some guys put a non-metalic spacer between the plenum and the IH's to reduce heat transfer. Maybe that would help your problem.

Jim

All good questions. Does the Size "thickness" of the Coolant outlet pipe gasket come into play here as well?

[secondchance]

Originally Posted by QB93Z

Bob, I just checked two cars, the 1990 and the 1994. In both cases there is 1/16 inch clearance between the coolant tube and the PCV tube.

Interestingly, when I lifted up on the PCV tubing to try to make contact with the coolant tube, I could not get them to touch. The PCV tubing contacted the under side of the injector housing bolt flange preventing contact with the coolant tube.

I wonder if your plenum's mating surface has been machined in the past to make a better seal to the IH's?

I don't know how the coolant tubes are sealed into the plenum, but I have always wondered.

Some guys put a non-metalic spacer between the plenum and the IH's to reduce heat transfer. Maybe that would help your problem.

Jim

Like Jim said, phenolic spacer may be the solution.
However, you have to make sure you have clearance between the underside of the hood and top of the plenum before taking that route.
I will check mine later.

[Locobob]

Thicker plenum gaskets are available, ask Jeff about them - he had some a while back.

[tomtom72]

This makes me want to go look at mine.....which I'll do this evening. I'll take some picts also.

However now that you bring this up I want to say that I think mine is configured the same as yours is configured, with that interference between the PCV hard line and the 90* elbow from the plenum, I think.

To your Q about the attachment method. On my spare 91 plenum those pipes are a press fit with some kind of hardening dope. Or at least the fittings on the 91 plenum I bought were that way. Now I do not know if the machinist who did the porting work removed and reinstalled the fittings? It's my opinion that if you try to move those you will break the seal on the "mystery" sealant used. I say this because when I pulled that elbow out the sealant was quite hard in it's dried ( set up or cured ) state. I can tell you for sure that is not any kind of standard pipe dope like teflon pipe paste or even RecTo-Seal ( the stuff used on oil & gas lines with threaded ends ). I also doubt that it's an epoxy, or how would I be able to break that elbow loose without distorting it? It reminds me of the old #7 aircraft sealant in that it dries to a hard state, except for the color. The stuff on my elbow was white to light tan in color. Sorry I can't add anything really useful.


Tom

[John Boothby]

Just checked my 90. The PCV line is dimpled where the two cross. Looks factory. I use the thicker gaskets from Jerry and they do not touch. However, it looks like they would if not for the dimple!

[Aurora40]

Originally Posted by tomtom72

Sorry I can't add anything really useful.

Tom

Not true, now I know not to try to twist it to a different position.

I'm not a fan of using a spacer, I'd be afraid of hood interference. A thicker gasket would be ok, but I'm not sure that would buy enough space? Also it means yet another plenum pull... I'm getting a bit tired of pulling it all the time. I might go the route of pulling the coolant elbow off and grinding that area down a little.

Though that will be a pain too because the last time I tightened the bolts on them, I got the feeling it was the last time they had in them.

[Jagdpanzer]

Bob,
I have you covered if you end up needing a few coolant elbow bolts.

[tomtom72]

okay I went to look at my car & took some pictures, 4 to be exact and I'll post what I think is the best one. The rest you can use the link to look at if you like.



This the link to my photobucket page:

http://s215.photobucket.com/albums/c...omZR1/my%2090/



Tom