[Formulabruce]

Originally Posted by shakerz

Any input as to the statement that 13's are not RAIII heads though they are passed off as such sometimes and could be found stock on Catalinas and other non RA cars?


thanx guys.

13's showed up on the high horsepower GP's, auto, and other 400 auto cars.
I know GM replaced 12's with 13's under warranty, They are so close in specs.
The 13's were in good supply. A friend ordered a pair of #12'S in 75, and got 13's
The reason they are often called RA heads is because they are, for the most part, identical to the #12 head.
I have only seen 13 heads on 4 BBL engines
my 2 cents