Radiator cap - RC15 or RC26

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Mar 17, 2010 | 07:11 PM

roy69

Thread Starter

Drifting

Joined: Feb 2010

Posts: 1,551

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From: Kulpmont PA

Radiator cap - RC15 or RC26

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threads indicate the two caps are made for different radiator materials, and some threads indicate the RC26 simply superceded the RC15 as a part.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?

Mar 17, 2010 | 09:17 PM

Mike Ward

Race Director

Joined: Jul 2001

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

Mar 18, 2010 | 10:15 AM

Alan 71

Team Owner

Joined: Sep 2006

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From: Westminster Maryland

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

Mar 18, 2010 | 11:25 AM

bashcraft

Le Mans Master

Joined: Jan 2006

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From: Butler Pa

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

Mar 18, 2010 | 02:54 PM

Mike Ward

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Joined: Jul 2001

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Quote:

Originally Posted by 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

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