Well lets start for the start. I have 3 motors (2 complete, and a short block) all are 302's. 1 complete is a roller (came from a 1989 grand marquis, converted to carb. ) and the short block is a roller. the other is a 1971 stock motor. I also have 2 sets of heads one is from a 351 and the other is a 302. now that you know the backround here is the big deal. 1) what motor would be best with what set of heads? 2) can I put a regular head on a roller block? 3) would a 351 head on a 302 block give me more hp? thanks for all yall's help Alex O.
I would use the Roller block with the 351 heads,,,,,,, Unleaded fuel engines are design to take more heat,, leaded gasoline like the 71 ran cooler,, and with unleaded gasoline,, it tends to get the old engines a tadd bit hotter,, The other good thing is the one piece rear main seal,, if you want to get a little better HP,,, use a cam from a 351 windsor,,, your firering order will be that of the 351,, but that is pretty much what a 5.0 HO engine set up is.
Head selection should take into consideration the pistons. You could wind up with a very low compression engine or a very high compression engine if mismatched. I am only going by what I have learned from others, valve size and combustion chamber CC size, are key factors on a cylinder head. Cast aluminum or iron makes a difference, aluminum you can supposedly run more compression without detonation. Newer cylinder heads use roller rocker tips and or provisions for roller cams. I think that there is a small block Ford engine forum that is probably searchable?
Which 351 heads do you have if they are pre 72 use em, if not probably small valve smog heads (yuck) the older block will have more meat in bores/main webs but the roller ones are good too.Depends on the power level you want to be at.You can use the older heads on roller blocks but you will have to step up to screw in rocker studs/push rod guide plates(dont use rail type rockers with a roller cam)or pressed rocker studs(bad gree gree there)Yes good 351 heads will make power on a 302 if its the short deck block.
Some casting numbers from the heads would help in the decision-making here... the large numbers next to the deck surface. If the 351s are D0O ... Those are good ... used 1970-74 ... if they are the ones after that (D5O ... ??) ... not so good ... Big variety in 302 heads, too. Long and short of it though is that most aftermarket heads will be better than any factory head if you can afford it. I have four pairs of better factory heads here that I may sell off to do just that ...
I'd say use your best roller block with 351 heads as well. Like mentioned though... we await casting numbers on the 351 heads. Not all 351 heads are an improvement...
Ramp speeds/valve speeds with roller cams and rail guided rockers so you dont need pushrod guide plates??? Dude... thats just asking for valve train failure at an inoppertune moment.If you are running a hydraulic non roller cam...in a mild application thats fine.Better to be safe than sorry.
