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Slight Miss at Part Throttle
427 S.O. Edelbrock heads and intake, MSD dist. Holley 950 HP carb. The engine idles perfect WOT is great, the plugs are a nice tan color, but at part throttle, it has a slight miss every 5 seconds or so.
It seems to be only coming from the right bank. I'm lost. |
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Are you running all mechanical advance or do you have a vacuum advance distributor? It sounds somewhat like an over-advanced condition I had with my BB Corvette motor with a vacuum advance distributor.
A bad plug wire is another possibility. Seems they show up more under light load and idle than any other time. |
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No vacc. advance. All of the plug wire are from 120 to 130 ohm resistance. |
Sounds to me like a slight lean condition. Try opening the idle air screws up a quarter turn after first adjusting them for max vacuum at idle.
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At around what rpm?
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Just guessin'... :) |
Stumble or miss only at cruise or light throttle >>
I bet this is a lean condition stumble. I would ask for all the basic/normal stuff to be checked .... float level, manifold vac. OK or no leak, timing at this RPM?, total timing. Will it clear up if you add a bit more throttle ? It's a hot rod so add more timing and fatten her up a little more, increase RPM or get on the smooth side of the cam. Drive faster !!! |
Might still be too much advance coming in at cruise. Do you have a pretty quick timing curve or a lot of total timing in the motor like 40 deg? You might experiment by pulling a couple degrees of initial timing out of it or putting in the next heavier centrifugal advance springs to slow down the curve a little. The way you describe it as - a slight miss every 5 seconds or so - sure sounds like what I experienced in my Corvette.
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Solved:
The idle air screw ghost must have stoped by one night. I could have sworn I checked them, more than once. I guess not. Both screws on the right were open only about 1/2 turn. :CRY::CRY::CRY:. Sett all four to a 1 1/2 turns out, runs lake a champ. Put well over 100 miles on it this weekend, never hiccuped once. |
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