I've just ordered a Griffin aluminum 31x19 radiator, PN/55272, dual 1.25" rows. This is going in a 1978 Malibu with a 454, aluminum GMPP heads, 12.4:1 compression motor. What pressure rating to I want on that radiator cap? More pounds=more pressure=cooler running, correct? Let me know what you suggest. Also, this is the first aluminum radiator I've ever bought, and was wondering if I have to purchase some sort of a special cap for it? Thanks.

more pressure = higher boiling point.
so, instead of boiling at 212 degrees without a cap, it might boil at 240 with a 15# cap.
or something like that.
and boiling water in an engine is bad. if you have all good hoses and all seals are good, i'd run the highest pressure cap you can find. i think newer cars and trucks have 25# or so caps.

Each pound of pressure raises the boiling point 3 degrees.
I run a standard 15 lb cap on the same size aluminum radiator...it works fine...never over 180*. :thumbsup:

I believe NHRA is mandating 20# caps starting in 06.
Can`t remember if contigent on ET or not.

I've got a Stant 16 psi cap on mine.