Hi All

I just picked up a 390 FE, on the front right side and rear there are negative 105 cast in the block. Same place as you would expect the typical 352.

My own reseach says;

(1) the michigan plant produced these
(2) it signifies that the block was from 74 and up (1976)
(3) its a block that can be bored out to a 428

Is there a corect answer out there? any help would be appreciated.

Cecil

 

(1) correct
(2) correct
(3) you'll need to do the "drill bit" test to know, but only sonic mapping can say for certain.

 

AFAIK, the reversed 105 replaced 352 in 1972.

Verify that this is a 390 by measuring the stroke, because the 360 also used this same block.

The bore is the same (4.05"), the stroke is not: 360 = 3.50" / 390 = 3.78"

 

Not all will go to 428 bore- some have the cylinder cores of the 428/ 391-361 truck and will, some have "regular" 4.05 cylinders
410/428 crank should have a 1U, 1UA, or 1UB code cast in one of the throws, later 390 a 2U or 3U, 360 a 2T