Posted by TParker (IP: 4.33.1.93) on November 05, 1999 at 20:36:17:
In Reply to: I have a stupid question? posted by Craig Selvey on November 05, 1999 at 18:56:25:
The firing order is controled by the CAM not the crank. The cranks are the same and the pistons are actually going up and down in the same sequence just fired in a smoother order. The cam has to be different inorder to get the valves in the right sequence. Then all you have to do is change the order of the plug wires on the distributer. I change my '72 302 to the 351W firing order when I rebuilt it. You also get better cam options with the 351W firing order.
: You say the H.O. and non H.O. motors have the same crank....but a different firing order....how can that be?
: ================================================================
: : You're wrong on the firing order. Perhaps all post '76 truck engines had the 351W firing order, but the Crown Vic's had the old 302 firing order until 1990. Believe me, I know, we had a Mustang in the shop someone had replaced engine w/Crown Vic long block, car wouldn't run, had to switch ECM pins for the cylinders to make the firing order the old-style, I am not wrong on this one.
: : Forged Pistons started in 1985. They continued for awhile but where never available on the SN95 models. I think they started using hyper's 1992 or so.
: : I didn't know about the valves- but I knew the heads were different somehow. -CP
: : : All post '76 302s have the same firing-order as the 351W (1-3-7-2-6-5-4-8) regardless of whether it's an H.O. or not...Also, the H.O. had the 351w valves (1.84/1.54). And I don't believe the pistons are forged (although I could be wrong on that one); I think they were hypereutectic cast...
: : : : The non HO motors have a different cam, pistons, & heads. The cam is roller in the HO, the pistons are forged (up until 1993, I think, not sure). The firing order is also different, as the HO motors have the 351W firing order and the non HO's have the old 289/302 firing order. The best thing about the late model truck engines is they have the same block, crank & rods as the HO. So it is easy to make it an HO motor if you rebuild it. Buy a set of roller lifters and retainers, roller cam, good aftermarket forged pistons and a steel dist gear, and its basically an HO motor. (You cant convert the older blocks to roller cams because they are not machined as such; it can be done with aftermarket cam & lifters, though.) The HO motors also had a dual roller timing chain and a few other things to make less drag, but if you rebuild a late 302 well, its as good or better than a stock HO motor. -CP
: : : : : I have stumbled across a 1987 multi-port fuel injected 5.0 that is in a full size van. does anyone out there know how this motor compares to an 87 5.0 HO in the mustangs. (diff cams, compression ratio etc?) Thanks.