[jk294]

I just picked up a 1980 f150 4x4 with a 400m(not original motor), it has a bad knock to it. i was planing on replacing the rod and main bearings. i'm pretty sure i can do it with out taking the motor out but i want to make sure.

has anyone had any experience with this method?
it's that or i might pull the engine and replace it with something different say a 4v 4.6L or a 2v supercharged 5.4L or a 3v 6.8L v10 or a 7.3L powerstroke. but that would take a lot of work with the drivetrain.

let me know thanks.

[mrv8outboard]

Those 351M/400M engines had small bearing areas. Also wrist pin and cylinder wall issues. Just put a 460 in it. L&L has headers and mounts. Those engines share the same bell housing bolt pattern as the 429/460. I did it in my 1979 F150.

[StangGT1995]

If it's knocking, there's a very good chance the crank needs to come out for some machine work. It's not a simple job of just pulling the caps off and replacing bearings, if that's the case.