I just rebuilt the engine in my '68 and went with a larger cam. specs are 224-234 duration@.050", .465"-.488" lift, 114 deg. separation. I didn't think this was a very radical cam, but I'm only getting 10" of vac. I don't run a PCV, just breathers. Would a PCV help? What else effects vacume? Compression? It's 9.96:1. Too high? I'm taking it for state insp. and getting timing and carb adjusted right tommorrow. This is a 355 SB.

I believe 68' should have a pcv. This helps pull the bad air out of the crankcase and helps the rings seal which if they are not sealed your vacuum would not be as high. Won't hurt to try one.