Atten. Duke: Here's what I was able to obtain from my original 365HP gaskets: Both measured .017 in the areas that I was able to get a decent reading since the gaskets are rather dirty. In one corner, they both have a small GM on them as well as what appears to be a larger G with the letter V superimposed on top of it. No other identifying letters or numbers that I can detect under the crud. Hope this helps you in any way.
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Re: 1964 head gaskets
Thanks for the information. The thickness jibes with the Chev. Power Manual's ".018"", but I'm surprised your engine had single gaskets. I thought double gasketing continued into '64, but maybe not. The unshrouding cut added about 2 cc to the chamber with the larger valves, and the 30-30 cam reduced DCR because the inlet valve closed over 10 degrees later than the Duntov cam, so maybe GM decided that double gasketing was not necessary for SHP/FI in '64.
Can you do some more cleaning and see if you can find a part number?
The 3830711, which was apparently released circa '63 is thicker according to specs and actual measurements, and I suspect it may be a service only part number, or was not used in production until later.
Duke -
One other thing...
Can you check them with a magnet to be sure they are plain steel and not stainless?
DukeComment
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Double head gaskets?
This is the first I ever hear that GM used double head gaskets on an engine. I must say I have never observed this. I've pulled many original small blocks apart too. Is this practice specific to any particular horse power build or specific year? You are talking only about regular steel shim gaskets?Comment
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Re: One other thing...
Duke, the gaskets are plain steel. Could not find any identifying numbers. Might have to use muriatic acid on them to clean them up good. My "64 is a May 1 built car.Comment
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Re: 1964 head gaskets
uke,
Here's a pic of a brand new 340 HP 63 engine still only patially dressed. Difficult to tell for sure but I have to guess there is only one head gasket. I tried to enlarge this pic to about double size but the quality was going away so I posted the original. This particular engine was assembled some time in the 3rd quarter of 1963. Also of interest is the fact that there appears to be no stamped round hole in the ID tab. Could be that it's there and we just can't see it though. By the way, the SS 3916336 had a square hole for ID.
I wonder if it's possible to measure, with a feeler guage, the head gasket thickness while the heads are still on the engine? I seem to remember at least one area that would not have the gasket covering both surfaces. It may not be 100% accurate but this would certainly be close to a compressed gasket, or gaskets if that were the case.
Love the painted exhaust manifolds.
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Re: Double head gaskets?
A TSB discusses the practice that began as a running change in '62 due to customer detonation complaints. Only SHP/FI engines were double gasketed, and it's not clear when the practice ended. My March built '63 L-76 had double gaskets when I removed the Flint installed heads for the first time.
DukeComment
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Re: 1964 head gaskets
Yes, as a matter of fact you can, and it's quite easy. Also, I think it's quite accurate - plus or minus a thou if your technique is good and assuming the block deck and head surfaces are dead flat.
Using your photo as a reference, start at the corner where you can see the gasket. Insert an appropriate feeler gage or gage stack and then slide it up the gap along the front face of the engine, or slide in the gage(s) at several points along the gap. It's no different than checking valve clearance - find the largest gage or combination of gages that will slide in without using force. Many engine types allow head gasket thickness measurement using this technique.
I don't think you can eyeball single or double gaskets - it has to be measured. I have a double stack of stainless steel 336 gaskets and can see the square hole in the corner where it extends beyond the corner of the head.
The spec is .017" compressed, but I measure in the range of .036-.037" rather than .034". Could be that GM speced the minimum based on material thickness tolerance or there could be a thou or two of paint film in the gap.
It's a good check to do at engine assembly, but can be done at any time.
DukeComment
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Re: One other thing...
Thanks. I'm beginning to think that the double gasketing did not extend into '64. Previously I thought it continued beyond the end of '63.
Very early '64 SHP/FI engines had the "slow" '63 centrifugal curve, but with the late closing 30-30 cam inlet valve event and slightly larger chamber due to the valve unshrouding cut, it could be that double gasketing stopped at the end of '63. Could be, also, that the 711 gasket is a few thou thicker than whatever it replaced, and then GM found they could quicken the SHP/FI advance curve and this went into production early in the '64 MY.
L-79 has a greater propensity to detonate at the same CR because the valve closing point is earlier than the 30-30 cam, and this may be why they have a slower centrifugal advance curve with more total centrifugal and less recommended initial timing.
DukeComment
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Re: 1964 head gaskets
We used this method years ago, especially on engines with AL heads and comp gaskets. I think the numbers were, as you mention, within a thou.
I'm going to dig out the original photo and rescan at high res. I'm sure I can provide a much cleaner/crisper image.
I remember many of the 336 gaskets that were coming through in the late 60's, having numbers like .023", or more. One original print called for .016" but few were ever that thin. We talked to engineering and they talked to the vendor but I don't think it ever went anywhere. May have been in late 69, after the Trans-Am season ended and part spec's were no longer top priority.Comment
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Better Scan...
Hope this looks better.
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Re: 1964 head gaskets
Jack------
Your description of your gaskets are as I would expect. The "G" with the superimposed "V" denotes "Victor Gasket". Victor (now Victor-Reinz) was an original equipment supplier to GM. Other suppliers were also used and supplied these same gaskets. Among the other suppliers were Detroit Gasket, McCord and others. The "GM" indicates that the gasket, although manufactured by Victor, was supplied to GM for PRODUCTION or SERVICE.In Appreciation of John HinckleyComment
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