318 advice

Thats pretty much the same cam as the 280H from comp. it should ahve about 14" of vacuum, check the idle mixture screw settings. Get a vacuum guage and hook it to the intake at a good vacuum source like the brake booster line, and set the mixture screws to get the highest reading and it should make a difference in the way the engine idles. If it doesnt then the valve springs or the valve job is weak.