Miss at cruise speed ????

[SleeperScamp]

My 70 340 4 speed Duster has a miss, or stumble ,or cuts out ,or whatever you want to call it once you get up to speed... Runs fine when accelerating but when you are running at a steady speed you can feel it missing or cutting out.. Where do I start ?? How do I find out if its electrical or fuel ??? Thanks..

 

[BadAss71]

Do you have the points distributor still in it? From what your describing it kinda sounds like a worn out distributor.

 

[SleeperScamp]

Has electronic ignition. Where do I begin?

 

[Mikes270dart]

Could it be your carb? under accelaration you are using the accelerator pump in the carb to dump fuel into the venturies, but under part throttle crusing you are using venturi vacuum to draw the fuel into the intake. How old is the carb. do you have any vacuum leaks. Dou you have a second carb that you can try to see if the problem remains.

 

[SleeperScamp]

Carb is less than five years old... I have another but not sure its any better.. I may try that..

 

[1wild&crazyguy]

sounds like either bad plugs/wires or too lean.

 

[sr71mopar]

Too much vacuum advance can cause a problem like this.

 

[SleeperScamp]

BTW its a 750 Edelbrock...

 

[1969dodgedartgt]

i recently had the same problem,
it was a lean issue, had to adjust my carb to lift the meter rods out of the jets a bit.

dont know how that carb would adjust....

 

[ramcharger]

I'm thinking lean at cruise. If you were running a Holley I'd say go up two sizes on the primaries.

 

[moparchuck67]

Check for too much timing.