Oil cap

[D S.]

While rummaging through a box of parts my retiring Corvette mechanic gave me I came across an old oil cap with two ears, flat center rivet with four press marks, and outside the rivet embossed into the metal it says Engine Oil Fill AC-FC2. Anyone know what era cap this is?

Thanks,
Scott

[Louis T.]

Re: Oil cap

Hi Scott,

I am no authority on C3s, but it sounds like the steel twist-on oil cap described by Richard Prince in his Corvette Restoration Guide 1968-1982 as being used in some late 1972 base motor Corvettes. Apparently, it was similar to the 1970 base motor cap except for the wording stamped in a circle around the center rivet you describe.

Save the wave!

Louis

[Joe L.]

Re: Oil cap

While rummaging through a box of parts my retiring Corvette mechanic gave me I came across an old oil cap with two ears, flat center rivet with four press marks, and outside the rivet embossed into the metal it says Engine Oil Fill AC-FC2. Anyone know what era cap this is?

Thanks,
Scott

Scott-----


Yes, the AC FC-2 was used on Corvette small blocks from 1969-1970 and 1973-76+ for engines with stamped steel covers. It is also SERVICE for 1953-55 6 cylinder. It's even possible it was used in PRODUCTION for 53-55 6 cylinders; I'm not sure about that, though. It is a twist-on style cap. I don't know of any applications in which it was originally used for big blocks, but it will interchange with and be completely functional for any big block with twist-on style cap (i.e. all 65-70) originally using a Stant-manufactured cap.

The FC-2 was an oil filler cap of internal GM manufacture. It may have been used in PRODUCTION alternately with caps of Stant manufacture and may have been sold in SERVICE alternately with caps of Stant manufacture. The Stant caps always have a "button head" center rivet; the FC-2 has the flat center with 4 welds in a circular pattern at 90 degree spacings.

I know of no chromed version of the FC-2; all were bare steel and painted with the engine. When chrome caps were required for twist-on style applications, Stant supplied the cap.

The FC-2 was also used on MANY other GM applications in the 60's and 70's.

[D S.]

Re: Oil cap

Thanks, Joe and Louis. I had seen similar ones but without the wording around the rivet. Based on those I had seen I had assumed it was for small block applications.

[Jeff A.]

Re: Oil cap

It is a pretty common cap used from the 50's through the 70's.
Always used on a painted valve cover application.
Used in All GM the lines Cadillac - Pontiac - Olds - Buick - Chevrolet.
I have even seen them used on AMC, international, Jeep, and Checker.

Never seen one without the writing - usually covered by the paint.
It COULD be correct for any painted valve cover - although not always the original style that was installed.

[Roberto L.]

Re: Oil cap

The FC-2 was an oil filler cap of internal GM manufacture. It may have been used in PRODUCTION alternately with caps of Stant manufacture and may have been sold in SERVICE alternately with caps of Stant manufacture. .

Was it common to deliver the cars in the 69/70 period alternatively with FC-2 or STANT, or the typical cap was FC-2? At present my 70 uses a painted STANT cap, which came with the car, but could have been replaced in the previous years of my ownership...

Thanks

[Joe L.]

Re: Oil cap

Was it common to deliver the cars in the 69/70 period alternatively with FC-2 or STANT, or the typical cap was FC-2? At present my 70 uses a painted STANT cap, which came with the car, but could have been replaced in the previous years of my ownership...

Thanks

Roberto-----


I wouldn't say it was common, but it could have happened. However, every known-original 1969-70 300 hp engine that I've seen had the AC FC-2. This was a cap of GM INTERNAL manufacture. So, I'm sure its use was "highly favored".

[Joe L.]

Re: Oil cap

Was it common to deliver the cars in the 69/70 period alternatively with FC-2 or STANT, or the typical cap was FC-2? At present my 70 uses a painted STANT cap, which came with the car, but could have been replaced in the previous years of my ownership...

Thanks

Roberto------


One other thing to keep in mind: if I were looking at a 69-70 300 hp small block which appeared to have original engine paint and all portions of the engine, including the cap, appeared "homogeneous" as far as paint was concerned AND that engine had a Stant-manufactured oil cap, I would be strongly inclined to believe that cap was original to the engine.

If, on the other hand, the engine appeared to have been painted in whole or part post-Flint, touched up post-Flint, and the oil filler cap appeared to have been part of said re-paint, then I would be inclined to believe that a Stant-manufactured cap appearing on that engine was not original to it.

[Roberto L.]

Re: Oil cap

Thanks Joe, I think my car reflex the second situation. I found a partially repainted engine (paint over paint...) suggesting a rebuild or perhaps a quick "cleaning" before selling the car. So, I removed the paint, cleaned and repainted it a few years ago. I kept the S cap but I have in my mind's list of parts the other cap.

Usually If I suspect the paint is original I try to keep it, even with some small scratches as in my firewall paint, but in this case it was too late...

A mix between restoration and preservation.

Saludos

[D S.]

Re: Oil cap

Jeff, that one you show in the photo is in better shape than the one I found. I had to clean off surface rust and paint to even see the words. Some discoloration and pits on mine but the underside is in great shape.

[Joe L.]

Re: Oil cap

Jeff, that one you show in the photo is in better shape than the one I found. I had to clean off surface rust and paint to even see the words. Some discoloration and pits on mine but the underside is in great shape.

Scott-----


These caps are not too hard to find. I once walked through a "self-service" wrecking yard and picked up about 10 that were in superb condition. In fact, I walked away from more than that because they weren't perfect. One has to be careful, though because there are AC caps out there which appear identical to the FC-2 but they're stamped with other "FC" numbers.

[D S.]

Re: Oil cap

I assumed the cap wouldn't be rare. I have never seen one before. The 350/300 1970 I once owned had a Stant/SM cap on it. It went away and now I have a '70 big block and having the devil of a time trying to find a correct cap for it. I know it is supposed to have an S on the rounded rivet, no SM stamp and have a square rivet with a deep indent in the center on the underside. And it's not supposed to say 'Made In Mexico'. I think I do have a correct one for '60s big blocks. Like the '70 LS-5s but has an SM stamp near the rivet head.