Engine kickback on starter when warm?

1985 FORD E-SERIES VAN
132,000 MILES • 7.5L • V8 • 2WD • AUTOMATIC
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SHARKB8
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This is a motorhome. I rebuilt the carb, and it has a new(er) distributor i purchased a few years back. Everything runs fine, though probably a bit rich. When I first start the engine, it is fine. After warming up a bit or driving it, when I turn off the motor and try to restart, it kicks back on the starter. If I disconnect the distributor vacuum hose, it will start fine, no kickback. It was set at 8 deg. initial advance. I retarded the timing to about 5, and it seems to start ok with vac hose connected. The specs say 8 deg., so I'm not sure if that is okay.
I did change the main jets from .061 to .059, as it was running quite rich. It still seems to run rich. Could that be part of the kickback problem?
Thanks for your reply.
Dec 1, 2023 at 9:21 AM
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STRAILER
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At 132,000 has the engine been rebuilt or replaced? If not, there could be a fair amount of carbon inside the cylinders which can bump up the compression which at 8 degrees can cause the engine to kick back while starting. I would try it with the vacuum hose disconnected at 8 degrees to see what happens. If okay, block off the vacuum advance and run it. Please let me know how it goes.
Dec 1, 2023 at 5:00 PM
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SHARKB8
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As far as I know the engine is original. It has around 130 pounds compression, as I recall. I'll let you know how it goes with vacuum removed. The only vacuum available is manifold, which is stock for this engine. There's no carb connection. If I rev the engine and let off the throttle quickly, it will backfire a little bit in the exhaust. The engine has headers on it if that makes any difference. I don't have facility to check the fuel/air mixture, but it does seem to run rich. Any suggestions are welcome.
Dec 1, 2023 at 5:16 PM
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STRAILER
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The distributor should have ported vacuum (FYI), so I would try it with the vacuum line remove, it should help the problem. Let me know.
Dec 2, 2023 at 10:46 AM
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SHARKB8
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I set the initial timing at 8 deg, as per spec. I put one size smaller jet (58 from 59) in the carb. I let the motor idle for about 20 minutes. It did not kick back this time. I'll monitor it over time, take it for a test drive when I get a chance. I'm still not satisfied with how it runs, and there is popping back in the exhaust when I rev the motor and let off the throttle. But at least it's better than before.
Dec 3, 2023 at 6:26 PM
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STRAILER
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Good to hear, if you upload short video on how it is running, I can help more.
Dec 4, 2023 at 9:51 AM
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SHARKB8
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This is a link to another short video.. Hope it works.. Two more coming.
Dec 5, 2023 at 7:45 PM
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STRAILER
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Sorry, but these links try to download to a users computer which is not allowed on the site. Please use your phone to take the video and upload it here in your response, it can take a bit depending on your connection so be patient.
Dec 8, 2023 at 9:14 AM
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SHARKB8
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Well, I took it out for a local drive (no freeway), and I stopped by the bay to look again at the spark plugs. The color was beige, not black, so I can't really complain. And starting it again wasn't a problem. I adjusted the vacuum advance with a hex wrench counterclockwise about 6 turns, so maybe that helped. The engine seems to run good, though I'm sure it isn't perfect, so I guess I shouldn't worry about it.
Thanks very much for your help.
Dec 8, 2023 at 4:54 PM
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STRAILER
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Good to hear, please use 2CarPros anytime we are here to help.
Dec 9, 2023 at 8:56 AM
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SHARKB8
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Thanks very much for your time.
Dec 9, 2023 at 9:04 AM
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STRAILER
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You are welcome.
Dec 9, 2023 at 10:49 AM
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