Smoke
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7th Gear
Joined: Sep 2022
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Smoke
I’ve researched old threads but wanted some fresh feedback. My 74 F100 390 FE motor smoked when I let off the gas running 7 years ago when I parked it. I finally got it cranked and bringing it back to life. I don’t have rolling tires on it yet but setting idle it smokes,Not so much when I rev it up. It has a rebuilt short block from Advance auto but I think my father out the old heads on it. It has to be the head seals etc. right? Any chance the smoke is ring related?
Lead Driver
Joined: Jul 2017
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From: San Jose, CA
Presumably it’s smoking out of the exhaust. Correct?
How old is the remanufactured engine, and has it been run before?
Is this the same engine that smoked before?
Are you saying that the cylinder heads have been refurbished, or were the old ones put on the new block?
I’ve been able to get perfectly good engines to smoke out of the exhaust at idle by adjusting ignition timing too far retarded or advanced, but that’s probably a longshot.
How old is the remanufactured engine, and has it been run before?
Is this the same engine that smoked before?
Are you saying that the cylinder heads have been refurbished, or were the old ones put on the new block?
I’ve been able to get perfectly good engines to smoke out of the exhaust at idle by adjusting ignition timing too far retarded or advanced, but that’s probably a longshot.
Lead Driver
Joined: Oct 2018
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Probably a combination of all things. most likely your guides are loose and your stem seals are shot. possibly in brittle pieces.
The easiest thing would be some smoke stop product and it will help, but maybe not enough. next would be new valve seals they're not that hard to change. if that doesn't do it then pull it and begin the rebuild.
The easiest thing would be some smoke stop product and it will help, but maybe not enough. next would be new valve seals they're not that hard to change. if that doesn't do it then pull it and begin the rebuild.
Super Moderator
Joined: Apr 2004
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If it smoked when you let off the gas 7 years ago, it was the valve seals. The neoprene umbrella seals get hot, harden up, and then break into little pieces.
Pull a valve cover and see for certain.
They can be replaced with the heads on the engine IF the heads are otherwise sound. A compression test will give you most of the answer there. The other one is if they will hold water under pressure.
Good luck!
Pull a valve cover and see for certain.
They can be replaced with the heads on the engine IF the heads are otherwise sound. A compression test will give you most of the answer there. The other one is if they will hold water under pressure.
Good luck!
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7th Gear
Joined: Sep 2022
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Smoke out exhaust, same engine as before. I let it go without cranking for years. The short block is 14 years old and not sure what my father done to the heads. I suspect he used the old ones that leads me to believe it’s the culprit.
Lead Driver
Joined: Mar 2004
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Are you sure it is oil smoke ? What do the plugs look like ? Maybe it's the carb, that's a long time for one to sit.
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7th Gear
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The smoke is pretty bad at idle but not so much when I rev it up.
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