Off-Idle Hesitation

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These hesitation problems seem to follow us from one degree to another. I have a 418 with an 850 Holley that was modified by Jet Performance a few years ago. Once I got the motor past 1500 rpm or so it had incredible throttle response. But, I seemed to have this very slight off idle stumble, directly off idle. The Jet carb had the throttle blades drilled 1/8" which helped keep the motor inside the idle mixture range so I could smooth out the idle using the mixture screws. But, the holes were a little too big and the transfer slot was no where near the throttle blades when cracking the throttle quickly off idle. Changing squirters from 28 - 37 did not help at all, and only screwed up city driving with huge squirters by dumping too much gas in the motor. With a vacuum of 13-14", I swapped out the 3.5 power valve for a stock 6.5, lowered my floats, which were too high anyway, replaced the Holley baseplate with a Proform unit and gave it all a try on my brand new rebuilt 418. I have stopped chasing the off idle stumble and all is well now when cracking the throttle. The transfer slots, by the way, on the new base plate are exposed just a tad, and I think that may have been the final modification to set my particular off idle stumble to bed.

Bill