Power Valve Selection: The Definitive Answer

No road test yet, weekend rain and Momma's day, but did get it running in garage, warmed up good and just doing some quick checks with the a/f and vacuum gauge. With the 10.5" PV the idle readings didn't change, but when just doing some quick rev's (on primaries only, but includes the accelerator pump shot) it is now into low 11's on the a/f gauge vs. in the mid 12's I saw previously doing the same quick checks. Need to get it out and do proper testing but I can already see I'll need to go down on the primary jets (pvcr is fixed at .052, will deal with what to do with it being fixed later) and look at everything else...oh boy. Here's a link to the Holley forum where someone posted asking about selecting Power Valves, the Holley rep gives the standard line, but the op obviously knows a thing or two and the Holley rep then agrees that using cruise is the more accurate way, but that because most don't have a wideband, they advise using the 1/2 of idle vacuum. Just one thread I found as an example. https://forums.holley.com/showthread.php?169-Power-valve-selection


You can make the PVCR adjustable with some 6/32 brass set screws. You just tap the existing hole (after you drill it out to the correct size for a 6/32 tap) and then just drill the brass set screws to whatever size you need.

I think you'll find when the power valve opens sooner you can use a smaller pump shot and you may be able to lean out the mains further than you think as long as you can open up the PVCR.