Someone told me on this board that I measure what power valve I need by checking my vacuum at idle in gear, which for me is about 650rpm, minus 1inhg(Ithink that is what vacuum is measured in :confused: ). to get my valve opening time. When I checked this my vacuum is at 12inhg which means I need an 11 power valve right?

I've always heard the pv will be 1/2 what the vacuum is in gear. I.E....if your engine is drawing 13 inches of vacuum at idle then you need a 6.5 pv. I'm sure someone else will chime in soon and correct me should I be wrong.

maybe I was thinking of some other rule of thumb?????????????????

Dawg's got ya covered....
In MOST cases, the stock 6.5 power valve will work just fine.
When you get below 10 - 12" of vacuum, that's when you need to consider changing it.
It depends on who you ask..some say 2" below the manifold reading, some say 1/2. If you check the Holley web site, they recomend 2" below manifold vacuum, BUT if you E-mail their tech department, they'll recomend 1/2 the manifold reading.
(I actually did that once.) Personally, I recomend (and have always had good results) going with 1/2 of the manifold vacuum reading at idle.

in your case its not so important to worry about your power valve being 2" below your reading at idle in drive......poeple with very low vacuum readings of 7 or so below in gear at idle really need to make sure its not open while in gear at idle........

you for the most part have plenty of vacuum and your only worry should be that its not low enough(like a power valve that is rated say at 5") that it causes a dead spot while lightly pushing on the gas during cruise......the best thing to do in your case is to put the vacuum gauge on and go drive the car and see where your cruise reading is.......just to say..say if its 12" at cruise and you put a 11" powervalve in then all you are doing is using more fuel when you dont need it........because everytime you just lightly move the gas pedel it will open the power valve and dump fuel down the carb which you dont need....wastes gas..... you want the power valve to open as late as possable but before it goes to lean to creat a stumble......

so if you have 14" at cruise rpm going down the road and you have a 6.5" power valve in the carb and you just lightly dip into the throttle and feel a hesitation then your power valve is to low because the vacuum dont drop enough under light throttle to open the 6.5 powervalve.......so this is where the gauge comes in handy......if under light throttle your vacuum gauge drops to 8" the a 8.5" power valve will work just fine......because its just below the 8.5" opening rate.....as long as there is no stumble or hessitation that should be it....but if you still feel a slight stumble then go up to a 9.5" to open alittle more sooner......

the 2" below idle in gear is for the folks that have really big cams and low vacuum......with around 7" of hg or lower at idle.....

you just need to set yours for cruising and part throttle acceleration

I've been wondering because My car kinda hesitates when I'm cruising unless drop a gear with the kickdown. I'll test the vacuum when I'm cruising and tell you what I've done.