[fbodyfreak]

I am trying to choose the correct power valve for my engine, and I have a small idea of how to do it, and I know it has something to do with the vacuum that the engine produces at idle. I am getting 6" of vacuum at idle, because of the camshaft that I have, and I know the power valve that I installed when I built the carb is probably for an engine producing 15" of vacuum or more. Does anybody have any ideas or know the correct way to figure after you measure engine vacuum
thanks

sbc 400
RPM Range: 3,500-7,000
Intake Duration at 050 inch Lift: 244
Exhaust Duration at 050 inch Lift: 254
Duration at 050 inch Lift: 244 int./254 exh.
Advertised Intake Duration: 302
Advertised Exhaust Duration: 312
Advertised Duration: 302 int./312 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.510 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.533 in.

Lobe Separation (degrees): 114

Sportsman II heads 2.1 intake 1.8 exaust (I think)
trw 2477 pistons .145 dome
Approximate 11.65 static comp.

[ernkazern]

Does your car have an automatic or a standard trans? If it's an automatic check the idle vacuum in gear. What brand of carb is it? Holley recommends taking the idle vacuum and dividing it by 2. That will give you your power valve number. I know they make a number 35 which means it opens at 3.5 inches Hg. I don't know if they make smaller ones or not.

[fbodyfreak]

It is an automatic trans, and thank you for the information

[Joshua Lee]

Get a buddy.... Put the car/truck in 1st gear and check the vac. divide by 2 and you have the powervalve you need..They make a 2.5" thats what I have...Suposedly they make a 1" but I havent ever seen one..