1971 Radiator Cap?

[Greg F.]

I need a new radiator cap for my 71 small block, 4 speed, with Air Conditioning. The radiator is the original brass harrison. Which cap is correct? I'm confused by the RC 15 / 26. Some vendors place them together for the same price. Is one for an expansion tank equipped vettes(my car does not have an expansion tank)? Can someone give me the exact cap I should order?

Thanks you for the help!

[Patrick H.]

RC-15 *NM*

[Joe L.]

Re: 1971 Radiator Cap?

Greg-----

As Patrick mentions, the RC-15 is definitely the correct cap. The RC-26 was designed for use with aluminum radiators or aluminum supply tanks. Some confusion is generated because the RC-15 was GM-discontinued some time ago and is REPLACED by the RC-26. The RC-26 could always have been used in place of the RC-15, but the RC-15 was never a good choice for applications requiring the RC-26. So, I presume that GM figured if they were going to discontinue one or the other, the RC-15 was the best one to get rid of.

[Terry M.]

Re: 1971 Radiator Cap?

You should read the story in The Corvette Restorer a couple of years ago written by none other than Patrick Hulst. Then you will know what to look for to identify a real cap from a poor imitation, and how to tell a SERVICE replacement. Of course if function is more important than judging, you don't need to read Patrick's story.