John Cailey said

Just never heard of .520 as being the accepted max lift before having to cut down the guide bosses? Could be. Variables I was referring to are spring retainers used, keepers used, suggested ( by the cam Mfg.) spring installed height, new guide installation height. At any rate, I didn't have a clearance problem with my set up.

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mechanicmark said

For what it's worth, i got a 72 Demon this summer. It has a mild built 318 consisting of stock bottom end and cylinder heads. It has headers, duel exhaust, and edelbrock performer package. This is the performer manifold (not rpm air gap) 600 cfm. carb. jetted of economy (1406) and their small performer cam, like 204* duration and .420 ish. lift. Car ran best of 15.4 seconds at Earlville this summer with 904 trans. and 2.76 open diff. a very nice running streeter. 17-18 mpg. But boy is that going to change!!

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