I will say when I jetted down a tad on my primary main jets and drilled my P/V channels I measured my jets with my drill gauges and the P/V channels and did not care about the jet number as I dropped .003 in size on my main jets by size and not number and opened up the P/V channels the same amount. Course that's because the Holley jets are not always the size of the number on them mostly when you get into the mid 60's and up. Ron