The largest cam I ever used on a street 235 is in the motor I just took out of my 57 (new 261 going in although that has been a fiasco all of it's own. Look for the thread chamfering rod bearings if any one is interested. I am still not done fixing the "new" venolias yet). I built the motor in 86. the cam was the most reliable cam I ever used and was a Chet Herbert regrind 280 duration and .480 lift. Did not hit the stock pistons, I did not shave the head or block. Used dual springs I got from Clifford (I never did figure out what they were actually from) and aluminum retainers (yikes!). I used trw pushrods, they were much better than stock, used a small block chevy 1.6 exhaust valve, clearanced the pocket for the larger valve and got rid of the little bump out on the chamber wall that stalls exhaust flow for a bit. Motor had a loopy idle at about 900 rpm, and made power from about 1800-1900 rpm to about 5300-5400 rpm where the head ran out of air. That motor was in and out of my 57 four or five different times as I replaced it with other motors but when the other motors quit or puked bearings or something, that one always stayed together. I never did clay up the pistons to see exactly what clearance I had. That being said, I would think a cam in the range of 268 - 278 duration with a lift of .450 -.470 would probably be a safe bet with stock pistons. As for the dual pattern grinds, i would love to try one at some point. Clifford did sell them, and may still offer them, but the difference in expense is just too great. The exhaust ports flow lousy no matter what and my all out 235/261 racing days are long over and anymore I am just happy finding a cam grinder to make me up a cam so single pattern is ok with me these days.
