Medium, Heavy Or Extra Heavy Duty Trucks With 330, 361 or
391 CID Engines
If piston scuffing and/or broken rings
on the No. 1 piston are found in Ford Trucks with 330, 361
or 391 CID engines, the cause may be due to a timing cover
bolt which is too long.
If you find a bolt with a flat head
which is 3/8-16 x 3-1/2" with a washer, which is the
third bolt from the bottom of the cover as shown in the sketch
below, replace it with the correct bolt-a self-locking bolt
3/8-16 x 3-3/16" with six notches on the head.
FRONT COVER INSTALLATION