will J heads work on a 318? And many many more questions.

dodgetkboy78 said
Other than the valve guides hitting the retainer, how is it too big? Considering a flat tappet cam doesn't spend much time with the valve open at max, and a 302 head 318 will pull decent to 6K......

Just the owner of more than one 302 headed motor here curious about your theory.

My untouched 302-headed 1970 318 with 256/262 (adv.) Lunati Voodoo cam (.454/.475" lift) pulls to 5500 cleanly but I shift a little before that because I can feel the powerband start to go down at that point (and I start to hit valve float). Maybe if I had a bigger intake, maybe if I had headers, maybe if I shimmed up the intake springs to spec'd installed height, it would keep pulling but this engine is old and starting to show signs of wear so I'm not too worried about it. I'm just saying that with a larger cam the engine might gain a little up top but it will lose grunt on the bottom end which wouldn't be helping with 3.23 gears and a mild converter. He can go ahead and use it but he won't be getting that cam's full potential without at least porting his 302s and will be needlessly giving up torque on the bottom end.

If it's your only choice go ahead and use the Crower cam for the time being but the engine will be over-cammed unless you bump up the compression and get the heads flowing well.