Radiator cap pressure


I have a stock Superformance MKII that uses the Roush 427 SR engine. I use the car on the street---no track work. I am wondering what radiator (head tank) pressure cap pressure people are using.

Thanks for your help,

/s/ Chris Kennedy

Howard Jones

Here: I use a 16 PSI cap. It seems to work fine. There is no reason that you can't keep the coolant temp under 260F in an engine that is working properly. That would be the boiling point of coolant (2/3 water 1/3 antifreeze). If it's over that then it can only be uncontrolled airflow, the pump isn't running efficiently or it is underfilled with coolant.

Note: The oil cooler and its related system are a big part of the total engine cooling capacity

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I think I have a radiator cap from one of the last AU III falcons in Australia for mine, and that only runs a pressure spring in the region of 13 or 14psi if I remember correctly.

IE this was all the ford Australia deemed necessary on the V8 falcons.

The rating of the thermostat is probably more critical in terms of when it opens and how hot it lets the engine run. If you just using it as a street car, I would assume that keeping it cool and not stressing it is more important than out and out performance, so not chasing the last few HP that may be gained from a hotter engine, increased clearances, or hotter combustion cycle?
Where do you live Chris. If you don't live in a very hot area and it's easy to keep your cool a 13-15 lb cap is fine.
Thanks---I live in San Diego, and am closing in on about a 15lb cap. The car does NOT overheat or run warm---I'm pleasantly surprised at that! I have run out to the desert in it to the east of here as well!

/s/ Chris Kennedy