66 L72 Valve Cover Cap
Did the valve cover cap change from black to silver in the 66 car year? If so, does anyone know when it happened?
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Re: 66 L72 Valve Cover Cap
Chrome BB valve covers in 66 used in Chevelles and full size cars used a chrome oil fill cap.Comment
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Re: 66 L72 Valve Cover Cap
Jim------
No big block Corvette ever used a "silver" cap.
1965-67 were black, except 1967 L-89 which was chrome.
1968-70 which used chrome valve covers had chrome filler caps
1971-74 used rubber "push-in" filler caps
All the 1965-72 big block filler caps were of Stant manufacture.In Appreciation of John HinckleyComment
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Re: 66 L72 Valve Cover Cap
Jim,
Do you have a silver cap you could post photos of?
GaryComment
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Re: 66 L72 Valve Cover Cap
Jim- I have an unrestored ,very original L72,and it has a "silvery" oil filler cap. Maybe it was black originally,and the black paint has worn off over the years, but I really do not see any remnents of that, and it looks to be about the same age as most every thing else on the car.
Interesting question,and I wish I could post a photo ,but I recently got a new phone, and have not figured out how to post pictures.
E.J.Comment
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Re: 66 L72 Valve Cover Cap
E.J. and Jim------
One possible reason for what you've found: there are lots of reasons that an oil filler cap could need to be replaced. For instance, in the "old days" folks would take their cars, including those considered iconic today, to the corner gas station for an "oil change and lube" (in fact, my only work experience in the automotive industry was as a very part-time "gas jockey" and mechanics helper at a Chevron station during my junior and senior years in high school). Oil filler caps could be "lost" but the station had plenty of replacements in stock. In addition gaskets could break or otherwise deteriorate and were not easily replaceable so a new cap would be installed.
The GM SERVICE cap, GM #3835665, was a "natural" finish and no black-finished cap was ever available from GM. As far as I know, save for the much more recent reproduction parts industry, no black painted cap was available in the aftermarket.
So, if a cap was replaced it would be replaced with a "natural" finish GM cap or an aftermarket zinc finished cap. Both were very likely to be Stant caps with an "S" embossed on the center rivet.In Appreciation of John HinckleyComment
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Re: 66 L72 Valve Cover Cap
Hello Guys - the original oil filler cap for these cars was Black Oxide & oil that over time tends toward a slight greenish hue.
Its not paint in any way shape nor form, black oxide (I have re-done oil caps) comes from taking very hot object and immersing into NaOH. OK, it eats the paper gasket and turns the inside black too.
No paint is going to get close...especially if you are intending to have the car judged.Comment
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Re: 66 L72 Valve Cover Cap
The information I provided above is basically applicable to the GM #3835665 oil cap from about 1965 and later, not earlier.
A little more information on this issue:
The GM #3835665 oil filler cap is a VERY old part number. While it might appear to some that the number sequence implies about a 1963-64 released part, it's not. This series of part numbers in the 383xxxx range were used out-of-sequence and date back to at least the early 50's. They were used almost exclusively, if not exclusively, for engine-related parts.
The configuration of this cap varied over the years and I have seen many of the variations. For the earlier versions, those from the 50's to early 60's, I have seen several different configurations and finishes. Some are zinc plated, some are natural steel, and some are painted black. Most of these have an INTERNAL rivet head with the peened end on the external surface. The internal rivet head has the Stant "S" on every one I have seen.
Some later versions are natural or zinc finish with the internal rivet head but with no "S" on the rivet head. Instead, the later style Stant logo is embossed on the outer surface of the cap.
I believe the version of the cap used for 1965-67 big block had the internal rivet head. I do not know if it ad the Stant "S" or if the external surface was embossed with the later style Stant logo. However, I strongly suspect that it had no external embossment.
I have NEVER seen a cap, SERVICE or PRODUCTION, that I believe was black-oxide finish. Among other reasons is that I have noted, as have others, that the 65-67 big block oil caps seem to "degrade" to a very slightly greenish hue. This would not occur with black oxide.
The GM #3835665 was finally discontinued from SERVICE in May, 1976 and replaced by a succession of several different part numbers. The first 3 replacements were the AC manufactured caps as used for 1969-70 small blocks and the last two were later style plastic/metal caps. The last one, GM #10110855, was discontinued without supercession in August, 2000.In Appreciation of John HinckleyComment
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Re: 66 L72 Valve Cover Cap
Im certain you’re incorrect
I had the print in hand and searched out a local conversion coating company to do a batch of these caps in conjunction with Paragons founder.
i was also involved at GM in all these plated and a painted technologies while these parts were still active in the GM system!
in the 70’s no one was chasing greenish hue
they would be worried about that thirty years on
and it all is explained in the chemistryComment
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Re: 66 L72 Valve Cover Cap
Ronald------
I said that I had never seen an example of this cap that I knew to be black oxide finished; I did not say that absolutely none existed. Perhaps they existed but I never saw one. All of the ones that I have seen, including NOS originals, that were black had "chips" off the black and/or the black finish appeared "thick". Characteristics that could only be accounted for by paint and not black oxide. So, I know, for certain, that the caps were made with black painted, zinc plated, and plain steel finishes. Were they made black-oxide finish, too? I don't know as I've never seen one that appeared to be black-oxide. Could some have been made that had a black phosphate finish? I don't know as I've never seen one of those, either. However, I would more expect the possibility of black phosphate than black oxide.
By the way, no one I know of, and certainly not myself, is "chasing" the "greenish hue" oil filler caps. For one thing, the "greenish hue" is something that develops over time and not the original condition.
I did a little further checking on this. It turns out that there was another part number for the 1965-67 big block oil filler cap, GM #3856959. This was a 1965 released part number and it was a PRODUCTION-only part number, never available in SERVICE. For SERVICE, only the GM #3835665 was available from day-one. It also turns out that a section of the GM blueprint for that part is included in Noland Adams' 63-67 Restoration Guide book. That section is included below.
You say that you have a blueprint of the cap in question showing the specification of a black oxide finish. Let's see it.
GM#3856959 Oil Cap.pdfIn Appreciation of John HinckleyComment
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Re: 66 L72 Valve Cover Cap
Too bad those that know more of this aren’t chiming in
the greenish brown hue comes from FeO interaction with heat and perhaps oil.
Joe reread what I said about the print.Comment
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Re: 66 L72 Valve Cover Cap
Just to add to the mystery...
This zoomed in and rotated GM image (dated November 1965), can be seen in itz entirety via Noland's book.
You can see the 'early' square font style of the 'S' on the rivet, as well as the faint circular 'SMC' logo.
I'll let our members decide if they feel the oil cap is painted or plated... perhaps a tough decision.
And remember, since the 'S' changed over time, so too could have been the black 'coloring'.
Oil Cap (11-65).jpgComment
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Re: 66 L72 Valve Cover Cap
Really great you posted this picture
one little point of reference
I did all this engineering work plated and painted at GM, back when these parts were active, if there is anyone on the forum that has done the same, step forward!
And I am still active in the field should you see my air cleaner bases offered with OEM paint as a reference
sooooo
It’s not painted
paint would have filled in the fine Stant details
Also the print for this was in the hands of the resident Tonawanda expert
One would need to be looking at the Mark IV engine “as shipped” prints
I will stand firm as I have for many years, since I restored a 66 bb while Ncrs was in its infancy, from the prints.
get the original print for any part to know exactly how the supplier made it
when I get a moment I’ll post pics of the resto work I did as mentioned so those doubters can see greenish black fresh from the black oxide bathComment
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