large-diameter distributor cap adapter?
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large-diameter distributor cap adapter?
I am using my stock points distributor (and cap) to trigger a high-output ignition. Plugs gapped at .050".
it runs fine at idle, but add any rpm or load, and it gets rough and starts backfiring.
i'm suspecting cross-fire under the cap. Is there a large-diameter distributor cap adapter other than the screw-in type? similar to the one for the late 70s V8s?
thanks-
it runs fine at idle, but add any rpm or load, and it gets rough and starts backfiring.
i'm suspecting cross-fire under the cap. Is there a large-diameter distributor cap adapter other than the screw-in type? similar to the one for the late 70s V8s?
thanks-
Fleet Mechanic
Joined: Nov 2002
Posts: 1,643
Likes: 69
A large diameter cap wouldn't hurt, but with the symptoms you describe I am not sure that the large diameter cap is the solution to your problems. Other areas to look at would include rotor registry, the amount of centrifugal advance, the rate of centrifugal advance, a cracked cap or faulty wires, or other problems not related to spark.
How much compression ratio do you have?
What RPM range are you trying to get to?
Do you need .050 gap?
For that matter, do you really need the high energy components?
My Last Logghe altered is using an ancient Mallory dual life points distributor.
Original, small cap.
I have a hotter coil with it.
It has 12:1 compression.
It has .035" plug gap.
It will rev to 6000 + RPM.
I think I would mark the location of the cap terminals on the distributor housing, remove the cap and check the rotor registry.
Check the amount of centrifugal advance by twisting the rotor and noting the amount of springiness in the mechanism.
Put in plugs gapped at .030".
Put on a stock coil.
Drill some vent holes in a stock cap.
See if it still behaves poorly it is time to look at other factors.
How much compression ratio do you have?
What RPM range are you trying to get to?
Do you need .050 gap?
For that matter, do you really need the high energy components?
My Last Logghe altered is using an ancient Mallory dual life points distributor.
Original, small cap.
I have a hotter coil with it.
It has 12:1 compression.
It has .035" plug gap.
It will rev to 6000 + RPM.
I think I would mark the location of the cap terminals on the distributor housing, remove the cap and check the rotor registry.
Check the amount of centrifugal advance by twisting the rotor and noting the amount of springiness in the mechanism.
Put in plugs gapped at .030".
Put on a stock coil.
Drill some vent holes in a stock cap.
See if it still behaves poorly it is time to look at other factors.
Thread Starter
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Posting Guru
Joined: Mar 2006
Posts: 1,182
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Thank you, FF- I'll check these.
Its the same distributor I've been using, so the centrifugal advance should be okay. I did swap the cap and wires, and I guess its possible I dropped the distributor in one tooth off.
I'll post back after I've had a chance to go through it.
Its the same distributor I've been using, so the centrifugal advance should be okay. I did swap the cap and wires, and I guess its possible I dropped the distributor in one tooth off.
I'll post back after I've had a chance to go through it.
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