390FE Knocking
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390FE Knocking
I have a 1971 Ford F100 2wd C6 tranny 390FE. The engine started knocking. I removed spark plugs and found them really fouled and 2 of them crushed. I drained the oil and found it looked like sludge. I removed the engine and I'm now in the process of disassembling it. I suspect that my carb stud fell down the intake. So far I have removed rocker arm shafts and found a couple of bent rods. Can this engine be saved? Could a machine shop fix any internal damage? Do I need to start looking for another 390fe? Thanks for any advice.
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I had a heavy knock in my 351 that made me think I had a serious problem. It turned out to be carbon and went away on it's own. That was a relief. Carb stud? Do you mean the threaded rod in the middle of the air horn that holds the air filter housing? I can't see that getting through the carb and intake, maybe, if it broke or was short enough to begin with. It's almost impossible to say if the engine can be saved until we know what actually happened, but I would say that the fact that it was still running before you started taking it apart is probably a good sign. Since you're taking the engine apart, let us know what you find out.
Fleet Mechanic
Joined: Aug 2014
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From: Charleston, SC
Get a few more posts up so you can post photos of the engine once it's torn down.
Other than some kind of obviously catastrophic damage, only a machine shop can tell you if the engine is beyond repair.
Other than some kind of obviously catastrophic damage, only a machine shop can tell you if the engine is beyond repair.
Logistics Pro
Joined: Aug 2015
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From: Lind, WA- Eastern WA
Did the oil have a lot of metal flakes or shiny spots? Even if a stud did fall into the intake, it didn't mess up two spark plugs! The stud wouldn't go into one cylinder, then jump out, and into another cylinder. What does the fluid in the radiator look like? Is the fluid level low?
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I didn't see anything shiney in my oil pan. My intake manifold had a couple of ports with extreme carbon build up which could have caused problems. I have not took off the cylinder heads yet.
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The machine shop quoted me a price of $2500.00 to completely go through my engine, new pistons, camshaft and resurface everything. Or, I can get a running 390fe from the salvage yard for $1000.00. My budget is low so I am leaning towards the running junkyard engine.
Fleet Mechanic
Joined: Aug 2014
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From: Charleston, SC
You'll be rolling the dice on the jy motor, though. How badly do you need the truck? Is it your daily?
Mountain Pass
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Thanks for that advice. I'm also looking at a crate long block 390FE. The price is also about $2500.00. What would be a reasonable price for a used junkyard engine? If compression is good and can bench start the engine would it be something to consider? I am just trying to get as much feedback as possible before I make a decision.
Mountain Pass
Joined: Sep 2018
Posts: 136
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Thanks for that advice. I'm also looking at a crate long block 390FE. The price is also about $2500.00. What would be a reasonable price for a used junkyard engine? If compression is good and can bench start the engine would it be something to consider? I am just trying to get as much feedback as possible before I make a decision.