Help? Flathead running rough at part throttle.

andyg

andyg

Senior Member
So the 21 stub 36 LB engine started running rough at part throttle after monkeying around with a harmon collins magneto I had laying around. Put the stock (37-41) distributor back on and now it runs really rough at part throttle. I've spun it on the 1949 Allen distributor machine and it looks okay. I've tried timing it differently with no success.

Acceleration is smooth but a little weak and a quick rev up seems fine. Seems like the carb link is not returning evenly (dual 97's) but I think it strange that it ran fine, changed the distributor to the HC and back and now it doesn't run fine. :eek:

Any thoughts?
Andy
 
I checked the plugs and they look fine. I did a compression test and all looks normal for this engine.

I believe it's in the timing but can't put my finger on it.

Keep the suggestions coming!
 
Try a vacuum gauge, google it along with what different readings and what they mean. You can pin point many different problems with a vacuum gauge.
Just my .02 good luck and share your findings
 
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