Hey George & others,
To address the bogging at lower RPMs with the foot down hard, I swapped in the light secondary vacuum spring (original was medium). To my surprise, I got many more backfires and worse bogging. I checked the vacuum to see if I introduced a leak, but it looked fine. Timing 12 BTDC w/o vacuum, 36 w/vacuum and 43 or 46 revving up, if I remember the last two correct. Premium gas.
I think the plugs look alright, this is from 4 and 6 cylinders. The base of the plugs are still black, so shouldn't be too lean.
Engine seems to run great at higher RPMs, so maybe the secondary is opening too soon. I didn't see any check ball in the unit, but not all of them have that. Did yours? Holley.com says to start with heavier springs, move lighter until it "kicks", then back off to the next higher spring. Can somebody explain what a "kick" feels like?
Ideas other than put in a heavier spring?
