About 2 months ago I switched engines in my 78' F150 4x4. When I did I replaced rear main seal, front seal, and the main and rod bearings in my 351M. I put stock size bearings back in the motor and did not have the crank turned. The crank had very very small grooves wore in it and me and my dad decided that they might take a little life off of the bearings but should be ok. We put the motor back together and torqued everything to specs. After putting the engine back in the truck I drove it to go get gas at the station about 5 miles from my house. After leaving the gas station I proceded to drive down the road. I wasn't running the motor hard or anything and all of a sudden I hear a sound like the flywheel came lose and was rapping against the motor and bellhousing. Then the motor locked up and I heard a belt squeal. After pulling the truck to the side of the road I tried the starter. It just clicked, so naturally I thought I spun a bearing and ruined the crank. About 20 sec later I tried the key again and it cranked reeeeaallll slow. So I went and called my dad and we hooked on to her with his 78 F150 4x4 and pulled the truck home. while in the driveway I tried the key again, and the same thing real slow cranking. So we looked under the hood for some reason and was checking things out and after we concluded that nothing seemed to be out of place under there, we tried it again. This time it started cranking real slow and then it picked up speed and started. Since the incident I haven't had a lick of trouble with the engine and have put over 600 miles on the motor. I was wondering what caused this? The truck carries good oil pressure and runs fine. Someone told me that they have heard of bearings that will spin, get tight, then reseat themselves, I find this impossible cause of the little "ears" that are on the bearings. but maybe I'm wrong. Any input would be appreciated.

Thanks

Mine: 1978 F150 4x4 351M auto
Dads: (2) 1978 F150 4x4 351M auto
1 1977 F150 4x4 351M 4spd

 

Yes, it could have spun a bearing. The tang that holds the bearing in place could have been the cause of the tightness. Turn it over enough and the tang could have flattened out enough to let it run but it may not last very long. Good luck. Hope it isn't too serious.
Greg

'77 F-250 Camper Special 400ci driver
'76 F-250 Supercab 360ci current project
'71 Mach I 429CJ in storage
'79 F-150 for parts
huct on foniks wurkt fer me

 

a similiar happened to my friends car yesterday. we assembled a 302 from a station wagon and put it in his mustang. we cranked it over and it did so quickly, then we tried it again and it would barely turn, we tried it a few times and finally it just started spinning freely and fired right up. we figured that there was just too much drag on the un lubricated bearings or something.