Ignition problem? 66 442

[Guest]

I am having what appears to be a missfire at steady speeds. The car is a 66 442, 400 four speed, 3:55 rear. The engine has headers, eldebrock intake and a new holly 670 avenger carb. The ignition is mallory unilight distributor with mallory coil and mallory 8mm wires all new. The plugs are new AC R43S.

Does anyone know of problems with this setup? The car seems to run great at wide open throttle but miss fires or stumbles at steady throttle.

Please help if you have ideas!!

Thanks...Steve

[Guest Dave Wyatt]

Try backing the timing off a tad. My 4-4-2 will do the same thing with the timing bumped up to the max for strip use. At a steady cruise under 3000 rpms, it will feel like a misfire and be somewhat jerky, but nail the throttle and it never misses a beat.

[Sgt Art]

You may also be experiencing a lean surge. When you go to WOT, it dumps a bunch of gas into the intake temporarily eliminating that. Try making the fuel mixture a bit richer by simply adjusting the butterfly choke a little bit. Check your plugs before and after. They should be light tan if the fuel mix is correct. Also, I prefer full manifold vacuum for the the vacuum advance as opposed to ported vacuum. See if that helps any.

[Guest]

Thanks for the replies guys. My plugs are very light tan and extremly clean. I am going to back the timing down to specs, (it is 2-4 degrees advanced over stock setting). I will try the manifold vacumn over ported and see what that does as well. Will report back!

[Guest]

I have set the timing back to specs and went to manifold vacumn for the distributor advance. Car runs great now. I think I had the timing advanced too far for normal driving. I do however like the manifold vacumn rather than using the ported. This seemed to solve a hesitation problem off-idle.

Thanks for all the help.