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Going from 7 PSI to 16 PSI radiator cap. Problem?

Posted By: MidPenMopar

Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 05:22 AM

I just got a new radiator cap that has a built in temp guage and i noticed it is 16 PSI rated cap. The one i have now is the stock 7 PSI cap. Any worries over this much change, or does it not matter?


Thanks
Stu
Posted By: SCATPK

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 05:33 AM

Stu, the factory correct cap is 16lbs. Are you using a stock radiator or something fancy? I have an aluminum unit and use a 16lb not sure what a 7lb cap would be used for?
Posted By: DirectSubjection

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 05:40 AM

Quote:

I have an aluminum unit and use a 16lb not sure what a 7lb cap would be used for?



Wouldn't that be used if you have a recovery system like new cars?
Posted By: MidPenMopar

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 05:45 AM

Quote:

Quote:

I have an aluminum unit and use a 16lb not sure what a 7lb cap would be used for?



Wouldn't that be used if you have a recovery system like new cars?



Yes i set up a recovery system. I got the radiator cap from the shop that recored my existing radiator. He said that 7 PSI cap was correct for this appication. Guess he was wrong?
Posted By: DirectSubjection

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 05:52 AM

But if you have added a modern recovery system, the type that sucks it back in from the bottom of the recovery tank rather than just being a catch can - wouldn't the 7 be the right one?
Posted By: 1_WILD_RT

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 06:04 AM

Pure water boils at 212 deg F at sea level..

Pure water pressurised to 7 psi boils at around 235-240

Pressurised to 16 psi iy boils at 260ish...

I think use of 7 psi caps ended around 1960..Turns out 64 was the last year...

I know your car should have a 16 psi cap..
Posted By: OzHemi

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 06:09 AM

You sure it's not a 710 cap Stu?




Posted By: 1_WILD_RT

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 06:12 AM

The famous 710 cap...
Posted By: RapidRobert

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 06:12 AM

All the recovery(& non recovery) caps that I have seen(& used) are 15-16 lbs. I have never seen a 7 lb one.
Posted By: DirectSubjection

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 06:14 AM

Quote:

The famous 710 cap...







OK - since your car was 16 originally it seems 16 is correct.


here's a quote from a Ford truck board I just found. They were roiginally 7lb caps.

"I've been through the radiator cap thing too. Seems everyone is correct in their answers. Here's what I learned: the 7 lb. cap is correct and neccessary if you are using your original factory as issued 50's or 60's radiator as stated by cdherman. The facts about cap {system} PSI allowing higher boiling points as stated by 44dwarf are true also. What we don't know is whether your radiator is original or a replacement model made in the last 20 years or so. The way I had it explained to me by a long time friend in the radiator biz was that any radiator made nowadays has a much stronger core and tanks and can stand the 13-16 psi caps that are used now which will benefit the overall performance of your trucks cooling system. I have had a 16 lb cap on my '66 since 1982 when I replaced the original radiator with no problems at all. I am assuming you don't have the original radiator in your truck so the higher psi cap should be fine with all else in proper working on your trucks cooling system."
Posted By: OzHemi

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 06:19 AM



Attached picture 4929338-4734394-STUSCREAM.gif
Posted By: aarcuda

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 12:51 PM

im another guy that never heard of using a 7lb cap.... 16 lbs sounds like the right one to me.
Posted By: MidPenMopar

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 01:21 PM

I now remember that the shop that recored my radiator gave me a 7 PSI as they said they felt an original 40 year old unit was safer using a less pressured system. I.E. not going to leak or fail as easy. Maybe just covering their butts on this issue?

Posted By: lewtot184

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 01:56 PM

i use a 7lb cap on my 65 coronet 440 6-pak moder. works fine with a recovery system. mopar had some 70's and 80's cars that used a 7lb cap. if your cooling system is marginal and the engine runs hot use a 13lb or 16lb cap. if your system stays cool then don't be afraid of a 7lb system. a higher altitude would probably want a 13lb or 16lb system.
Posted By: I go fast

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 01:56 PM

The problem with a 7 lb cap is engine temp when you shut it off.You know (or should) that the engine temp rises after shut off.If the cooling system is filled to the point it has little or no room for expansion,you know where it goes,out the overflow.A 7 lb cap won't hold the pressure.
Posted By: MidPenMopar

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 02:58 PM

Thanks for the advice guys i am switching to the 16 PSI cap and will see if anything changes for better or worse?
Posted By: John_Kunkel

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/07/09 08:24 PM

Quote:

I now remember that the shop that recored my radiator gave me a 7 PSI as they said they felt an original 40 year old unit was safer using a less pressured system. I.E. not going to leak or fail as easy. Maybe just covering their butts on this issue?



I've had a couple of radiator shops recommend the 7 psi cap when repairing "iffy" cores/tanks.
Posted By: MidPenMopar

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/08/09 12:09 AM

Here's the cap. Now why can't they make it so it sits straight on??

Attached picture 4930846-Magnumforsale011.jpg
Posted By: DirectSubjection

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/08/09 03:44 AM



Posted By: MidPenMopar

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/08/09 03:54 AM

Quote:







Yeah yeah, i know....
Posted By: MoparforLife

Re: Going from 7 PSI to 16 PSI radiator cap. Problem? - 01/08/09 12:32 PM

The use of a 16 lb cap will not interfere or has nothing to do with a recovery system efficiency. The caps used on a recovery system have different design tha non recovery caps. The have in addition to the outer sealing seal a center floating type pressure sealing disc that as the coolant cools and creates a vacume in the radiator/cooling system and it opens allowing to coolant to return to the radiator tank. That is why the hose or tube to the recovery tank must reach nearly to the bottom of the tank.
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