81 radiator cap

[John H.]

We just judged a 1981 corvette today. Chapter judging clinic.
The radiator cap was questioned.
Judging manual reads "Owners manual states correct cap is a RC-27, however
every 1981 car that has been judged has a RC-33 cap."
Question--what is the correct cap for NCRS judging points?

Thanks Big John

[Tom R.]

Re: 81 radiator cap

I'm reading a Third Edition dated March 99 which still seems dated so there may be a current version. But my copy reads as follows under the section titled Radiator Cap:

"While owner's manuals may specify an AC Type RC-27, original cars have only been observed with an AC Type RC-33."

So your observations are consistent with surveys originally used to establish the judging guide. Either cap will earn points but in terms of what was delivered to the dealer and from what I read...correct cap is the RC-33 and the RC-27 is replacement.

I believe the manual is providing instruction that underscores the incongruity identified between owner's manual and observations of low-mileage, original cars used when writing the manual. Sounds like your observations are the same...congratulations!

[Page C.]

Re: 81 radiator cap

Hi Guys,
Our 81 #s401010 has a RC#33 cap. It's a 40,000 mile car that we have owned since 1985.
Hope this helps,
Page Campbell