Need input from big cam users.

spinman1949 said
Rick and Snake,

Thx for taking the time. Nothing like dealing with lost mechanics. LOL I did a little fiddling with some air hose fittings and my compression tester so I can do a listen for leakdown test this weekend. Oh and there is one other equation that I did not think of. The power valve. My guess is the one in the holly is stock. 6.5 which works fine with a motor running 13 inches of vacuum at idle, but this sucker is pulling less than 6 inches which makes me wonder if I am not bleeding some extra fuel from the power valve. Holly tech says take idle vacuum and divide in half and that is your power valve selection. So my guess is I should install a 3.5.

Me and some others have gone back and forth on the PV issue. This is a issue i do have have personal experience with and Holley's recommendation is fine on moderate to high vacuum engines. When you get into the 12"ish range or less at idle you need to be just a few numbers under the idle vacuum. Problem is as a example a 8" idle number can become a 13-15" number at cruise rpm and if you used a 4.5" PV you need so much throttle movement to get there that you develop a flat spot under moderate acceleration. Idle to wide open is ok under there senario, but street cruising requires a different setup.

With that said, your vacuum readings are too low in my opinion and until you get the possible valvetrain and maybe timing issues squared away i would wait on messing with the power valve. 6" of vacuum is way to low for anything other than a full race cam or a retarded moderate street cam. You need to work on that first in my opinion.