Hey guys I have a 1986 f150 with a 351w I recently had the entire motor rebuilt from top to bottom and now it won't start, it has a very slow crank and seems lifeless, I've tried different batteries I've tried brand new batteries and still no luck, a few people said it could be the starter due to the motor having more compression now and I would need a more industrial starter but that doesn't sound right, anybody have any clues?

 

Timing could be too far advanced. Could also be a vacuum leak. Or read this before kr98664 pops in, because he's going to make you go read it anyway lol.

 

Darn tootin! Follow that troubleshooting guide. The test procedure disables the ignition, so it takes that completely out of the picture. If you have a starter that is slow to turn, or won't turn at all, that guide will pinpoint the exact fault.

 

To rule out timing just pull the coil wire and try cranking it over. If it cranks over fine it was timing. If not you may have a weak starter and the higher compression has now highlighted the issue.
Also be sure your cables are in good shape and the connections are sound.