Oil Fill Cap - 71 Small Block

[John Moore]

I am trying to put my 71 small block base engine as close to original condition as I can. I ordered a rubber oil fill cap from ZIP for my steel valve cover and it won't fit. Can anyone tell me if the oil fill holes in the stamped steel valve covers from 68 - 72 are different sizes? I thought mine were original to the car but now I don't know. Any ideas?

John

[Joe L.]

Re: Oil Fill Cap - 71 Small Block

John------

A bit of history of oil caps: for 1968, Corvettes still used the oil fill tube in the intake manifold and used a special twist lock oil fill cap on the tube. 1969-70 Corvettes also used a twist lock cap, but of a different style. Base engines with painted valve covers used an AC type FC-2 cap. All other engines used a chrome twist lock cap of Stant manufacture.

For 1971, Chevrolet VERY UNWISELY converted to the rubber, push-in type oil fill cap. This same style plug was used for small blocks through 1972 and for big blocks through 1974. In 1973, Chevrolet VERY WISELY went back to the twist lock cap for small blocks.

All of the rubber oil fill caps used for 71-74 were of the same functional size. Over the years there have been several different part numbers, but these varied only with respect to the configuration of the top of the cap and the lettering. The original push-in type cap used for your car was GM #3980273 and had the word "OIL" debossed on the top of the rubber cap. These letters were not hi-lited with any white paint or otherwise---just plain, black rubber letters that said "OIL" within a raised, black rubber circle around the perimeter of the cap.

This cap is the one generally available in reproduction and, I would think, should be the one that Zip provided you with. But, who knows? Keep in mind that you must lubricate the rubber beveled pilot edge of the cap with engine oil if it is to easily install in the cover oil fill orifice. Plus, you must change the cap about every year, or so, since the rubber hardens with engine heat making its removal and re-installation very difficult.

If you're not concerned about "correctness" of the top of the cap, you can use the current GM SERVICE replacement cap of GM #10110859. This cap fits all 71-74 Corvettes with the push-in rubber oil fill cap.

[Patrick H.]

Re: Oil Fill Cap - 71 Small Block

John,

Joe is right. You will need to oil the edge of the cap before inserting it. In addition, you'll likely notice that the font/lettering of the cap you received is slightly different than your original, assuming what your car had was still its original cap.

If you need any info on little details on your 71 base motor, let me know.

Patrick