roy69

I have a 69 with 427 390HP - no AC. When I got the car, the expansion tank (aluminum) had a pin hole leak in it. I purchased a replacement tank and ordered a new radiator cap as well. The new radiator cap is an RC26. The cap that was on the car when I purchased it was am RC15. Other than the stamping on the cap they look identical and are both marked as 15# caps. I have 3 manuals and I havent found any info on the cap other than it needs to be 15#.
Information in some previous threads indicate the two caps are made for different radiator materials, and some threads indicate the RC26 simply superceded the RC15 as a part.
Can anybody tell me which one I should have on the car?

Mike Ward

You need an RC26. The RC15 is for brass radiators.

Alan 71

Hi Mike,
I believe the radiators were COPPER and the overflow tanks were BRASS, when a RC-15 was used.
You know that but your fingers didn't!
Regards,
Alan

bashcraft

My '69 has a copper radiator and aluminum expansion tank with a RC-15 cap.

Mike Ward

Yes, you're right. It's the metal the cap touches that's important. Aluminum uses RC26, copper/brass RC15.

roy69

Thanks