Understanding the mid year expansion tank cap #307

[Larry M.]

I'd appreciate hearing from an expert (like Joe Luccia) to get me more knowledgeable on this topic. A couple of questions:

1. In a post over a year ago (different question) I received a response that led me to believe these small block caps were stainless steel. The one I have appears to be correctly configured and certainly vintage but is magnetic (which I "think" means not stainless). Were they stainless?

2. I'm seeing that AC made several 13# caps. The RC-9 for example is I think stainless and is for ford and chrysler products. But comparing it to my cap (only from pictures without dimensions) it looks like it would work just fine. Would it work or are there differences not so easy to see (like stem height) that would make it non functional on a 64 corvette?

3. If not stainless then I found this place called Corvette Pacifica on the web (link below) which offers repro caps which look very close to the originals but are zinc plated. Comparing their E1810 product to the cap I have the script for "TURN TIGHT" and "REMOVE SLOWLY" is a little big but otherwise it looks like a great repro. What I see at other major parts houses are totally incorrect. Does anyone have any experience with Corvette Pacifica products?

http://www.corvettepacifica.com/categories/70/cooling-system/0/48/

I would appreciate any help I could get on this topic.

[Peter L.]

Re: Understanding the mid year expansion tank cap #307

Larry -

1. The original AC 307 13# radiator pressure caps used from 1962 to 1965 were zinc plated steel. I don't think the AC stainless steel radiator pressure caps came in until the later 70s or so. I'm sure someone can provide a more accurate date. The 66 & 67 Corvette Owner's Guide/Manual under RADIATOR CAP state " The Corvette cooling is equipped with a 15 lb. zinc plated steel pressure cap." Unfortunately, I do not have a 1965 Corvette Owner's Guide to see what it says but hopefully someone will check & see if it says anything about the construction of the 1965 Corvette 307 radiator pressure cap; but I would doubt that earlier radiator would have had stainless steel covers & then AC went to zinc plated steel; but stranger things have been observed.

2. I have no experience with the RC-9 radiator pressure cap.

3. I also have no experience with the Corvette Pacifica radiator pressure caps but in general the reproduction radiator pressure caps have the STANT type under cover components not the AC components.

Pete

[Wayne M.]

Re: Understanding the mid year expansion tank cap #307

Larry -

1. The original AC 307 13# radiator pressure caps used from 1962 to 1965 were zinc plated steel. I don't think the AC stainless steel radiator pressure caps came in until the later 70s or so. I'm sure someone can provide a more accurate date. The 66 & 67 Corvette Owner's Guide/Manual under RADIATOR CAP state " The Corvette cooling is equipped with a 15 lb. zinc plated steel pressure cap." Unfortunately, I do not have a 1965 Corvette Owner's Guide to see what it says but hopefully someone will check & see if it says anything about the construction of the 1965 Corvette 307 radiator pressure cap; .......

Larry, Pete - the '65 Owners Guide (also) says "... equipped with a 13 lb zinc plated steel pressure cap"

[Peter L.]

Re: Understanding the mid year expansion tank cap #307

Wayne - Thanks. Pete