HELP - 390fe Running Horribly
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7th Gear
Joined: Oct 2025
Posts: 7
Likes: 2
From: Montana
HELP - 390fe Running Horribly
Hello all, I have a 1972 F250 highboy with the 390fe. It has always ran great for me, aside from eating a distributor and I’ve taken it on multiple road trips.
I drove it for a good 3 hour drive today, got to my brother’s place and shut it off. I went to leave about an hour later and it was running quite poorly. I took my brothers truck, came back an hour after that and then it wouldn’t hardly even run. After fiddling with the carb, patching vacuum leaks, and adjusting the timing, nothing has helped. I’ll attach a video as to how she sounds, thanks for any help!
I drove it for a good 3 hour drive today, got to my brother’s place and shut it off. I went to leave about an hour later and it was running quite poorly. I took my brothers truck, came back an hour after that and then it wouldn’t hardly even run. After fiddling with the carb, patching vacuum leaks, and adjusting the timing, nothing has helped. I’ll attach a video as to how she sounds, thanks for any help!
Fleet Mechanic
Joined: Aug 2007
Posts: 1,828
Likes: 253
From: Piney Woods of East Texas
Have you done any work to the engine? I would check the timing chain to see if it jumped a tooth. Without tearing the front of the engine down you would need to pull the valve cover and set cylinder #1 valves to TDC, then see where the timing mark is.
When you adj the timing was the flash consistent indicating it was firing every time?
When you adj the timing was the flash consistent indicating it was firing every time?
Thread Starter
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7th Gear
Joined: Oct 2025
Posts: 7
Likes: 2
From: Montana
I have not done any major work to the engine, no. When I checked spark in cylinder one it was good, but I do not have a timing light.
When I did adjusted the timing many months ago with my light, I found out the timing mark was already off so I just had to do it by ear.
When I did adjusted the timing many months ago with my light, I found out the timing mark was already off so I just had to do it by ear.
Thread Starter
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7th Gear
Joined: Oct 2025
Posts: 7
Likes: 2
From: Montana
The thing must have fixed itself overnight because she started up and ran fine this morning. I think it could have been vapor lock from heat soaking after my long drive. Not sure, but I’ll keep it in mind and update here if things persist.
Hotshot
Joined: Jul 2020
Posts: 10,452
Likes: 2,630
From: Near Salt Lake City
Along with the normal tune up issues
I see
Stuck valves, which sometimes means bent pushrods and broken valve springs creep up from time to time
How horribly does it run?
What ignition does it have?
I see
Stuck valves, which sometimes means bent pushrods and broken valve springs creep up from time to time
How horribly does it run?
What ignition does it have?
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