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'68 4 bearing head?

2941 Views 5 Replies 4 Participants Last post by  Jim Branham
There is this gt I want to buy, the fellow is telling me he had a 68 4 bearing head rebuilt with 1.74 & 1.5 valves with hardened seats installed, he used the 4 bearing head because it would turn higher rpm's ( more stable, ok) and was a higher compression head (I thought all the comb. chambers were the same cc's throughout the years). He is telling me this as a response to my question about the year the head is. My concern being the 4 bearing, 12 bolt head notorious for cracking on the late 72 & 73 heads. Has anyone heard of a 68 4 cam bearing head that gives higher compression? I would see for myself if it was the 12 bolt head but it is too far away. If it were a 3 cam bearing head, is it impossible to make it a 4 cam bearing head?
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The only head I can think of , especially for '68, is the 1.5 head. I don't remember how many bearings it had, but, I do know it had smaller combustion chambers. A guy here in Conyers races Opels on the local tracks and this is a trick he uses, as it raises the compression ratio the easiest way. Plus, it's a dead ringer for a 1.9 head on the outside (visual thing).
The '68 engine was a 1.5 litre (actually really only seen in Kadett) & had smaller combustion chambers, 3-bearing cam. All pre '71 heads are 3-bearing cam, 10 bolts, NOT hardened seats, but hardened inserts can easily be installed. No way to turn a 3 bearing cam head into a 4-bearing cam head. I have heard of installing a 3-bearing cam in a 4-bearing head by installing the unused bearing shell upside down to block the oil hole, but this seems like a bad idea. I don't know if a 4-bearing cam will work in a 3-bearing head. The 3 bearing cam is just fine for everything less than a race engine.

'71 and '72 heads are 4-bearing and 10 bolt (best choice), and although the factory claimed that they were suitable for unleaded, hardened inserts are worth the money at rebuild time (but NOT before!).

'73 head has 4-bearing cam, with flame hardened valve seats (for unleaded) which tend to crack, and the extra two bolts (to the timing chain case) which also tends to crack. Worse choice.

Thanks guys. This guy is sure it is a 68 head with 4 cam bearings and 10 head bolts,he got the compression higher by milling the head. The casting number is 3456716. Does this number help identify the year of the head at all?:confused:
What Keith has told you is absolutely correct. There is no such thing as a '68 4 bearing head. What has probably happened is he has stuffed a 4 bearing cam into a 3 bearing head. There is actually nothing wrong with this. The 4th bearing just "floats" in the air. While it is not optimum, I have built "weekend warrior" and race engines like this.

To verify what head is on the engine, have the person tell you what numbers are stamped into the head. The place to look is on the drivers side just in front of the rectangular plate that is held in with 3 screws. There is a flat "boss" that will have something stamped in it. Those numbers will tell you for sure what the head is.
head casting numbers

He told me these numbers: 3456716. Does anybody know how to decipher them or have an idea what site or thread I can look to find out for myself?
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