360 or 390?
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360 or 390?
I just bought a 1975 f-100 4X4 and was told it had a 390 motor. Problem is the VIN has a Y on the 4th digit which means it originally had a 360. The other problem with identification is that it also has a 4barrell carb which did not come on the 360s from what I have been told. The 390s did have that option. The blocks on the 360s and 390s all say 352. I could find out the stroke length with a rod but probably would not be to sure of myself and the results there. If I drop the oil pan, what would the number be on the crankshaft to identify the size of the motor for a 390 or a 360? I would GREATLY appreciate any help I can get, as no person Ive talked to seems to know.
Hotshot
Joined: Feb 2004
Posts: 11,697
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From: Marengo, Iowa
You will have to measure the stroke. I don't have the numbers, but I am certain they have been posted many times before, so do a search to find them. The only difference between the 360 and 390 is the crank stroke and the pistons, the bore is the same, the rods are the same.
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Thanks guys.
But I am having to drop the oil pan for a gasket leak anyway so I was just thinking that would be a easy way to see the size of the motor as well if it is on the crankshaft. I just dont know the number that would be on the crank to identify a 390 or 360. Are you saying the only way to truly know is measure the stroke and that I cant get it off the crankshaft?
But I am having to drop the oil pan for a gasket leak anyway so I was just thinking that would be a easy way to see the size of the motor as well if it is on the crankshaft. I just dont know the number that would be on the crank to identify a 390 or 360. Are you saying the only way to truly know is measure the stroke and that I cant get it off the crankshaft?
Post Fiend
Joined: Apr 2008
Posts: 8,261
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From: Big Sky Country
Thanks guys.
But I am having to drop the oil pan for a gasket leak anyway so I was just thinking that would be a easy way to see the size of the motor as well if it is on the crankshaft. I just dont know the number that would be on the crank to identify a 390 or 360. Are you saying the only way to truly know is measure the stroke and that I cant get it off the crankshaft?
But I am having to drop the oil pan for a gasket leak anyway so I was just thinking that would be a easy way to see the size of the motor as well if it is on the crankshaft. I just dont know the number that would be on the crank to identify a 390 or 360. Are you saying the only way to truly know is measure the stroke and that I cant get it off the crankshaft?
2U, 2UA or 3U stamped on the crank would ID it as a 3.78 stroke (390).
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