AC FC2 Oil Cap - Common on Buick Olds Pontiac, but Chevrolet?

[Tom D.]

A quick search here did not find "AC FC2". It's stamped with that code, and words that indicate it's an oil filler cap. Ebay offerings mention 1968-1974 Olds, 1968-1979 Pontiacs such as Firebird and GTO. GMC found also.

I just wonder if it has "usage" on Corvette or Chevrolet engines? A photo can be posted.

[David L.]

Re: AC FC2 Oil Cap - Common on Buick Olds Pontiac, but Chevrolet?

Tom,
My 1970 Camaro SS350 that I owned until 1977 had a "AC FC2" oil cap on one of the valve covers with a Made in Tonawanda sticker. The L48 engine was made in Tonawanda, NY. My 1970 Chevrolet Parts Catalog (exc. Corvette) lists the oil cap part number as 3835665. I have 2 used "AC FC2" caps in my collection that came with 69-70 Chevrolet valve covers with the Tonawanda sticker.
My Pontiac Parts Catalog (Sept. 1970) lists GM # 850843 for 68-70 All V8 and is described as "Type FC-2".
Apparently I have a NOS "AC-FC2" oil cap as well according to my photos that is slightly different as compared to the 1969-1970 type.
Dave

[Owen L.]

Re: AC FC2 Oil Cap - Common on Buick Olds Pontiac, but Chevrolet?

If it's part #3835665 then it was used for Corvette, according to the GMPartsWiki:

oil cap.png

The change over of part numbers appears to have happened in Dec. 1981.
#850843 it's listed for Corvettes with same applications as the part # above:
oil cap 2.png

[Joe L.]

Re: AC FC2 Oil Cap - Common on Buick Olds Pontiac, but Chevrolet?

Tom,
My 1970 Camaro SS350 that I owned until 1977 had a "AC FC2" oil cap on one of the valve covers with a Made in Tonawanda sticker. The L48 engine was made in Tonawanda, NY. My 1970 Chevrolet Parts Catalog (exc. Corvette) lists the oil cap part number as 3835665. I have 2 used "AC FC2" caps in my collection that came with 69-70 Chevrolet valve covers with the Tonawanda sticker.
My Pontiac Parts Catalog (Sept. 1970) lists GM # 850843 for 68-70 All V8 and is described as "Type FC-2".
Apparently I have a NOS "AC-FC2" oil cap as well according to my photos that is slightly different as compared to the 1969-1970 type.
Dave

Dave------


The FC-2 cap was used on 1969-70 Corvette small blocks with steel valve covers and, I believe, most other small blocks of the period. They were also used on Corvette small blocks with steel valve covers after the foolish "rubber plug" experiment ended. In addition, I believe they may have been used on 50's and 60's 6 cylinder applications

The FC-2 cap was also used on many other GM cars of the period. I once went through a self-service wrecking yard and got a whole bagful of these things painted in the different engine colors of the GM car lines. I still have that bagful around here somewhere. I do recall that a few of the caps had a different FC- number but they appeared very similar or identical to the FC-2's.

I believe the FC-2 cap was a cap actually manufactured by the AC Division of GM.

The 3835665 cap was not an FC-2. It was the GM SERVICE equivalent of the FC-2 although it may have also been used in PRODUCTION for some applications. I believe it was a Stant-manufactured cap.

The GM part number for the FC-2 cap was GM #850843. However, while this is a very old part number dating back to the 40's or 50's, it was first cataloged for Corvettes in 1976. The 3835665 was discontinued from SERVICE in May, 1976 and replaced by the GM #850843 which, as I just mentioned, was actually a pre-existing part number. The 850843 was finally discontinued in March, 1982 and replaced by GM #6410893. The latter was discontinued in October, 1983 and replaced by GM #6410961, aka FC-91. After that:

6410961>December, 1988>12334506

12334506>January, 1991>10110855

10110855> discontinued without supersession August, 2000.

[Joe L.]

Re: AC FC2 Oil Cap - Common on Buick Olds Pontiac, but Chevrolet?

One more thing: the FC-2 cap could have been used on big blocks; it has equivalent functionality to caps that were used. However, I've never seen a known original big block, Corvette or otherwise, with an FC-2 cap.