misfire while maintaining speed

[Tandrayray]

70 duster 318 edelbrock 4 barrel factory dizzy with points.
i just removed the distribtor to clean due to siezed adv. weights
wile cleaning i found that at one point the weights would stick.
after thinking i had fixed that issue, i reinstalled and now wile driving under load
no missfire but when holding the throttle to maintain speed i get a muli misfire.
once i step on it it goes away. thoughts?

 

[mguner]

It sounds like you are getting too much vacuum advance. That would fit with vacuum dropping upon opening the throttle. Check it with the vacuum unhooked.

 

[RedFish]

my guess is a worn out dist'. Shaft wobbles around, lobes worn down, advance plate rotates out of center. Any and all change point gap.

 

[roccodart440]

Either way it wounds like a dizzy issue. Considering you are running points I'd use this as an excuse to upgrade.

 

[AJ/FormS]

While all previous posters have valid opinions:Assuming the point gap and timing are correctly set, I would agree most strongly with post #2. And if,when you have proved its not either of these, Its also possible that the low speed fuel circuit is not functioning correctly.