I have a 75 Powerwagon that may have a cracked head (452). My only spare complete heads are 516 off a 66 383. I don't have the down time to have hardened seats installed right now, so how long can I expect this motor to last before the heads give up.

Also, going to the closed chamber heads, will I notice much of a power gain?

Vinny

As for the heads lasting, it may surprise you. In our experience the Mopar heads have lasted a long time with UL gas. A lot longer that either brand X heads.

w/o hardened seats it depends on how hard you run it before there's a problem & you drive like an old lady anyhow don't you Vinny so I think you'll be good.

Vinny you'll feel the difference if you use the 516's just from the CR increase alone especially when towing where the not as good port design of them wont affect you as much at lower rpm's.