Holley Power Valve Experimentation

I ran a 2.5 PV to start We used a digital vacuum pump and a moroso tester. As soon as it moves record the vacuum , That is what you would read. Vacuum at idle divided by two or less is the size PV you want to start with. After its installed you can fine tune the number using your EGT gauge . Better to start lean then rich. Most street holley's come with a 6.5 PV commonly used for 13-15 in hg