Allis WD-45 rough engine

[x1000ac]

My WD-45 will fire on 4 cylinders only when under load. Otherwise it seems to run on only 3 cylinders. All ignition parts are new and the fuel system is clean. Any suggestions would be apprecitated. Thanks

 

[nomind]

Sounds like a vacum leak at low rpm, and when the gov. engages the vacum leak is overcome.

 

[Texas Denny]

Do you have Champion spark plugs. My WD ran like you describe when I rebuilt and started it with new Champion plugs. After checking everything and resurfacing the manifold, I pulled the new Champions and put in an old set of AC plugs. It runs perfect with the old AC's. Had good luck with Autolite as well. I know this doesn't make sense - it is just what happened.

 

[x1000ac]

The engine sounds like there may be a leak, so I think you are right. I'm a "shade tree" mechanic and have never removed a manifold, so will I be able to remove the rusted nuts without breaking the bolts? The AC45 was bought new in 1953 by my family, has worked many hours, but has had a pleasant retirement for 30 years. Thanks for your advice. Any other suggestions?

 

[x1000ac]

Thanks for the advice regarding a vacuum leak. I replaced all the manifold gaskets and now the old WD-45 sounds like the day it was delivered new in 1953. It runs great. Thanks again.