[Tom Vaught]

14) Hate it when people say "remove the Power Valves in a "Race application."
There are so many classes in racing that a generic statement like that usually screws up the guys who Bracket Race and need to leave the line cleanly and have the proper Air/Fuel Ratio throughout the entire run.
You need to determine your specific racing situation and tune all of the circuits for best performance vs "Block both of the Power Valves" as a generic statement.
The Power Valves are only 'the switch'(s) in the carburetor.
The Power Valve Channel Restrictions control the actual fuel flow when the Power Valves are open.
The Power Valve Channel restrictions work from the time that the Power Valve first opens until there is sufficient vacuum in the engine to close the Power Valves.
Also a higher number Power Valve 'leads the Duck" before the Duck and the "Shot" from the shotgun actually get together.
You will always "miss the Duck" if you calibrate for the exact spot where you "see the duck".

The gentleman recommended a idle vacuum number divided by 2 and if on an 'even number' GO LOWER on the Power Valve number.
This way you will be even farther "behind the duck" when you need to be "in front of the Duck".
Holley Engineers used to say: Highest Vacuum Number (because the vacuum dances around with a bumpy camshaft and then divide by 2 and ADD .5 to the number. So 12" of vacuum /2 = 6 PLUS .5 so the correct valve would be a 6.5" valve not a 5.5" Power Valve.
That whole number difference is the difference in smooth performance that discourages racers so they take the valves out completely trying to fix the LEAN MISS.

So we have covered the actual Power Valve switching.

Now the Power Valve Channel Restrictions are controlling added fuel BEFORE the Main Jets really come on line.
It takes more signal to move a big glob of fuel thru a Main Jet quickly vs a smaller amount of fuel thru the Main Jet opening and then on to the Primary Metering Block Power Valve Channel Restrictions.
It should go Idle Circuit, Transition Circuit, Power Valve Channel Restrictions for moderate load, then Main Jets and Power Valve Channel Restrictions Together for WOT. The Booster is working once the main circuit comes on line but the amount of fuel thru the booster is best controlled by Both Circuits working together.

More on this in another post later

Tom V.