Recently bought a 79 F-150 4X4. Come to find out the engine had been swapped at some point and the parts I had bought for the 351M I thought it had wouldn't work. I located the casting #'s on the block which narrowed it down to either a 390 or 428 built between '67 & '70. Does anyone know how to pinpoint for certain which it is? Thanks
@SoHum2Az Engine code Y are 360 blocks G and H are 390 blocks Other than measuring the stroke is the only way to find out if it is a 428 than taking the engine apart. Most external parts will interchange. A Cheaper endoscope type camera that attaches to a smartphone may help. Measure with plug out and piston at top of stroke. Rotate to bottom of stroke. Mark camera lead at bottom of stoke and retract. Measure. This could be accomplished with a stiff wire or other device. 3.98" is a 428 stroke.
