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Mountain Pass
Joined: Mar 2006
Posts: 145
Likes: 2
One more shot
I have a 1954 ford 1/2 ton 239 ohv. Problem I have is a slight unstable idle and a flat spot when i first give it gas. I have original new carb that had been setting for a while so put a new kit in but no change. Also i have new distributor, ignitor module with flame thrower coil, plugs and wires. It will idle but its not smooth kind of low and high. Does anyone have any ideason the idle and flat spot on acceleration. Thanks
Tuned
Joined: Jan 2016
Posts: 333
Likes: 9
From: Oregon
Possible vacuum leak somewhere is my first suspicion. Check all vacuum fittings, vacuum operated components, intake manifold, etc. Might even spray some carb cleaner into the valve cover and see if engine speed changes. The flat spot could also be a faulty accelerator pump or vacuum advance. Check timing/advance and coil voltage at the ignition post, also. If no problems found, might do a compression test for something not right with the valves or rings. Good luck
Elder User
Joined: Sep 2015
Posts: 688
Likes: 6
From: Central PA
Possible vacuum leak somewhere is my first suspicion. Check all vacuum fittings, vacuum operated components, intake manifold, etc. Might even spray some carb cleaner into the valve cover and see if engine speed changes. The flat spot could also be a faulty accelerator pump or vacuum advance. Check timing/advance and coil voltage at the ignition post, also. If no problems found, might do a compression test for something not right with the valves or rings. Good luck
Laughing Gas
Joined: May 2010
Posts: 1,125
Likes: 191
From: Wharton, PA
I had a similar issue with my 223. tried everything mentioned here with no luck. Finally stumbled across the problem by shear luck. Had a bad spark plug in #4. found it by pulling plug wires and nothing happening with #4. tried swapping wires still no luck. Pulled plug and it sparked but not a bright spark. Stuck an old plug in it and it fixed the problem of stumbling. Ended up changing them all to a different plug
Mountain Pass
Joined: Sep 2017
Posts: 235
Likes: 25
From: Solvang CA
Vacuum line is a good start. Don't rule out more than one problem.
I know you gave a refresh to carb, but...are you 100% sure float was OK? Set a right height? No leaks? These floats can leak after a while.
Did you have all the parts for accelerator pump (mentioned above) according to drawing, and are you 100% sure you put in a new one? Like a lot of things, old one can look ok, but is not ok.
Lots of complaints about Champion plugs new out of box if you have those, not so many about Autolite. Maybe worth at least a check on cylinder nearest firewall on passenger side.
I know you gave a refresh to carb, but...are you 100% sure float was OK? Set a right height? No leaks? These floats can leak after a while.
Did you have all the parts for accelerator pump (mentioned above) according to drawing, and are you 100% sure you put in a new one? Like a lot of things, old one can look ok, but is not ok.
Lots of complaints about Champion plugs new out of box if you have those, not so many about Autolite. Maybe worth at least a check on cylinder nearest firewall on passenger side.
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