Cylinder Head Question
Thread Starter
Instructor
Joined: Jul 2006
Posts: 141
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From: Fort Kent Me
Cylinder Head Question
Just picked up my 91 C4 from the repair shop. It initially went in to repair an intake manifold leak that developed while I was 200miles from home. So I had no choice but to have it worked on at a AAA shop. Problem is while they were pulling the no 8 spark plug for replacement antifreeze came pouring out. All other plugs where dry. They sent the head to a machine shop for inspection and it cam back with a passing mark. The shop mentioned they thought it was a problem due to a bad aftermarket gasket. They also left me a note on my bill that my heads have "enlarged" coolant ports and they said to keep an eye on it. Has anyone ever heard of this? The gentleman I bought the car from says he has not had the heads off but the gaskets are definitly aftermarket. How can I tell if the heads are stock and could it be that this mechanic doesn't know what he is talking about? I have the old gasket and you can see where the no 8 coolant imprint was bordering on the fire ring. Any input would be greatly appreaciated. Car drove fine on the way home, but I had an argument with the shop because they told me that the radiator fans were not coming on when they should and I think that I am dealing with a shop that has very little experience with these engines.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Even though your heads should have the "113" stamped on them, the '91 is different from the earlier 113's in that the front and rear intake mounting holes are counterbored for intake gasket retainers. Those retainers are built into the intake gaskets which are difficult to come by - Dealer only as they are exclusive to the '91 Vette. You can get away with gaskets that don't use them, but it's difficult to maintain alignment as those counterbores make the bolt hole considerably larger. You want GM part # 12525814 and it includes the runner gaskets. The '91 F Body and the ZZ4 crate motor use a similar design, but they don't include the restrictors on the rear coolant passageways.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
How would a misalgined intake gasket cause this? The coolant port is not even close to the intake opening. Seems it'd leak into the lifter valley first.
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Thread Starter
Instructor
Joined: Jul 2006
Posts: 141
Likes: 0
From: Fort Kent Me
Actually it was the headgasket that seemed misaligned. The coolant jacket opening on the No. 8 cylinder was on the edge of the fire ring due to the skew of either manufacturing or installation. I'll upload an image of the old head gasket over the weekend.
I was able to determine that my heads are the stock 113 heads.