Hello everyone, I am posting this for a friend. He has contact with someone who has a set of open chamber 842 heads with Jan 67 date codes. It is thought that most 842 heads were closed chamber, does anyone know about these? Could them be a gm anomoly? Any help appreciated.... YOu are the best... tony D
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Re: 67 3919842 open chamber heads, Real?
if you were careful you can hand port closed chamber heads to open chamber. some will and some will not. i have a set of early pre production cast OC heads i got from chevy back in the 60s but i will have to see what casting # is on them.
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Factory 842's were closed chamber.....
and when the 69 L-88 open chamber came out, speed shops were quick to open the compustion chamber. They could not match the chamber of the real mccoy, but, close, hence the head porters referred to the modified heads as semi-open chamber.Comment
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Re: 67 3919842 open chamber heads, Real?
Tony -- From what I see in "How to HotRod Big Block Chevs" '71 edition, they show a photo of a sectioned (sliced) closed chamber head with a sketch of the maximum amount of metal that can be removed without entering the water jacket, and it's about HALF the distance to duplicate exactly the open chamber shape. Therefore I have to agree with George that it could only be a half-open chamber modification.
Do these heads (Jan '67) have the first digit of the part # ground off and re-stamped with a "3" ? This is how my August '67 "842" head appears, and that's the earliest I had ever seen.Comment
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Re: 67 3919842 open chamber heads, Real?
Tony-----
GM sometimes produces more than one finished cylinder head PART NUMBER from the same CASTING number. However, the differences are ALWAYS within the machining parameters established by the basic casting. I think that I can say with absolute certainty that GM would NEVER have produced an open chamber, finished, big block cylinder head from a casting designed for a closed chamber head. Such a piece would have been WAY OUT of the machining parameters established by the basic casting. In fact, I doubt that GM would have done such a thing even on an experimental, non-production-intended cylinder head. It falls almost in the category of machining a small block crankshaft from a big block crankshaft casting.In Appreciation of John HinckleyComment
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Re: 67 3919842 open chamber heads, Real?
I have two sets, obviously closed chamber, of mid February 842s but I have never seen any Januarys. Maybe that white L-88 wasn't too early... (just kidding)
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