would running too "numerically small" of a power valve cause a very rich condition? I run a very large camshaft, Howard 302/310, 268/278@.050 on a 108 installed straight up, in my 350. Im running a 750 mighty demon with the idle ease adjusted all the way open and a 2.5 power valve. It idles great but it is way too rich and it seems too rich throughout the power band but if i hammer on it with too small of jets it seems to not pull as hard on top end leading me to believe it would be a lean condition. Demon wont even talk to me about it cause they say "you need the race demon" but i dont need replaceable emulsion circuits or boosters 'cause i dont have a dyno and without a dyno none of that is really useful. SOOOOOO isnt the proper way to "size" your power valve to
1. Take manifold vacum reading
2. Divide it in half and go for the closest one???
I shouldnt have much manifold vacum with the cam thats why i just went with a 2.5 in the first place. What do you all think, could it be the power valve? Or am i way off base?

I have tuned on a Speed Demon some,if all 4 of your idle screws are open more than 1 1/2 turns or so its rich on the bottom.I try and run a power valve about 2" under idle vacuum when in gear.

a cam with that much overlap will be rich (have a strong exhaust smell) no matter what.

All spot on! Answer to the first question is clearly no. Yes take the reading and you can use a PV at that number even, as long as your idle curcuits are all adjusted. And with 4 corner, that's no sweat. ( I run a 105 and idle at 10 or less. no prob. 6 corner idle )

another question...how come the new power valves are not stamped on the side like they used to in the old days? The only numbers I see on the newer powervalve are on the face of it,how do you read them now?