Coolant overflow bottle cap pressure...

petex19

petex19

True Classic
Well my new to me stainless steel coolant overflow bottle is at the local "perma buff" getting pollished to a mirror finish as we speak so I wanted to pick all the experts brains out there about the cap pressure.

I honestly never knew that X's had a spec pressure for the cap but I read on a different thread that it is 12 lbs. My old cap which wasn't original but it came with the car was only 7 lbs. and the one I just purchased over the winter while my coolant bottle was being chromed :sigh: (hopefully my pollished stainless bottle will bring me as much excitement) is 13 lbs. with a pressure release flip thing on the top of it which I'm not sure exactly what that is for but it looks racy so I bought that one.

I guess my question is "Is my 13 lbs. cap okay or should I go and buy a new one that is 12 lbs. or less? "

'PeteX1/9
 
Steel tanks have a deeper neck too

The steel and stainless steel tanks from the early Xs have a deeper neck than the late model plastic tanks. I am not sure how important it is, but the proper cap for the steel tanks is a bit longer to account for the additional depth.
 
just go to any autoparts store

Ask for a 78 GM locking cap rated at 13 lbs. Only nine bucksand works perfect: -)
 
Just a generic rad cap from local auto parts store...

My old cap came with my car but I see them all the time at the local auto parts store. Rad caps come in various pressure ratings from 7 lbs. up to over 13 lbs.

The one I just purchased is a "Prestone" 13 lb. rad cap but they did have 11 lb. for the same price but not knowing any better I thought that more was better.:hrmph:

'PeteX1/9
 
Peter... yur fine with 13 lbs...

My experience and documents said originally 12.8 lbs and I believe the '74s, or SOME of the '74s were 7 pounds.

Anyway... your system will easily support 13 pounds and that will up the boiling point about 39 degree so that at about 260 indicated... your coolant will still be in a liquid form. Not recommended... but that is the idea.

I have used a 13 pound Stant cap for about 100 years and it works just fine...

Now go chrome something and put this subject to bed.

OH... one thing Jim said... NOT all SS tanks have a deep neck... but indeed, make sure that the cap seal is compressing aginst the inner lip. I think the two depths are 1 inch and 1 1/4 inch.
 
Pete you like bling...

I think I'm going to try one of these just for the hell of it and lose the Stant.

This should go with your Red theme bling :)

http://www.jegs.com/i/Mr-Gasket/720/2470R/10002/-1?parentProductId=874786
http://www.jegs.com/p/Mr-Gasket/Mr-Gasket-ThermoCap-Radiator-Caps/874786/10002/-1

radcap.jpg
 
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