The reason I ask is this:
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Da Grump (in The Chevrolet Racing Engine)</div><div class="ubbcode-body">The 4224 idle circuit requires some "fixing" in order to achieve a clean idle with a radical engine. The idle circuit in the number 5913 primary metering block supplied with the 4224 was originally designed for a carb with a power-valve system. The 4224 doesn't have a power-valve circuit and the idle circuit may be very rich with the normal race engine idle settings.</div></div>
And then he goes on to the bit about the 0.017" diameter wire in the idle feed restriction. I was reading that the other night, and I thought "why not just put a power valve in it then? I drive on the street, and it might cut down on some unnecessary fuel consumption while cleaning up the idle and off-idle mixtures at the same time!"
I don't experience backfires very much, but I figure I'd probably install power valve protector check valves while modifying the carbs for power valves.