Originally Posted by Busguy
The engine was recovered from an '84 3/4t, had reman tag so don't know origin. If the heads are '84 (low comp?) that will mean I need more initial spark advance-- currently set at 0 deg because this engine is mounted in an antique pusher bus, and can't hear it ping. Anyone know how to ID the heads, or failing that, how much spark I dare give it? The distributor is points equipt off early Lincoln, no carbon inside. Bus weighs 25k, need everything the engine can do.
In 1984 the 460 was the light truck engine in the 3/4-ton F250 pickup. The cylinder heads used were the D3VE-A2A heads, but the markings of the cylinder heads were not in the normal location at the top of the head. Instead, they were marked on the underside of the head, beneath the intake ports, cast into the underside of the head, look at the picture below/casting number is on the intake flange (underside) between the pushrod holes in the head:
This is the typical casting number location on 1984-1985 D3VE-A2A's and 1986 E6TE-DA's.
From the factory, that engine has about 7.5-7.9:1 compression ratio, and a very poor advance curve in the distributor. So yes, you can play with ignition timing by advancing the distributor, but beware of inaudble detonation in these engines
. It is not always there and the detonation control is correctable, but by all means do spark plug readings if you are playing with ignition timing in a 25,000 pound vehcile.
Generally, on pump gas with a 1984 460 I would think that 30 BTDC @ 3000 rpm is okay. Problem is that with your poorly advancing distrbutor, you will have to really twist it over in order to get that much advance at 3000 rpm, and this will result in high igniton advance at idle. Your best bet is to recurve the distributor, but don't get too agressive with the advance curve (due to the weight of the vehicle).