Finally getting my 40 on the road and doing the final carb tuning. I didn't want to wait for QF jets, so I called Holley/Quick Fuel tech support and asked if they were interchangeable. I was assured they were all the same, so I worked with the Holley jets while waiting for a QF jet board to come. I trusted that advice and have been through tuning hell until this morning when I put the 74 Holly Jets in the same row as the QF74's. They are so different you can see it with the naked eye. I don't remember the exact size difference but its on the order of H74~QF69 or 70. Thought this might help someone in the future.
It helps to have a set of gauge pins to match up a set of Holley type Jets...... That's what I use.. Those and a 0-1" o.d. micrometer...
Above^ is correct. SOME, and I mean SOME have the same hole........ BUT- Then one's number hole, doesn't equal another's.........The MFG = Holley/QF both have charts for diameter of orifice in relation to stamped # on a jet. Good post for those who do not know these things!
There's also a chart that Holley has that shows the actual hole size and the number stamped on the side of the jet.... You might want to look that up.... The o.d. mics are for checking the gauge pin o.d. size by the way.....
Interesting. I'm surprised there's a difference since Holley bought Quick Fuel a few years ago. I'm considering buying a pair of their adjustable metering blocks for my 4150. Not meaning to hijack the thread but anybody use their metering blocks?
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