Use a computer from the same engine size and the same year. You're going to introduce a huge new variable with the engine size; no sense adding another one with a different year computer. Anytime you have to run to the salvage yard for something, you're going to have to figure out which part you need for which year and which engine size.
I wouldn't try to modify the engine wiring harness. It is surprising how many pins both computers have in common, but going from six to eight cylinders will mean more injectors to fire and different plugs on the engine. Life will be much easier if you use the harness for the right engine.
The flywheel is matched to the engine and the Engine Computer because it has a ring with cutouts that are detected by the crankshaft position sensor. Those cutouts are different among different years.
Normally the 318 has been an internally balanced engine which just means all of the counterweights are forged right on the crankshaft. I don't know if that ever changed after the 1980s. The 360 used a cast crank that was externally balanced. There is an offset weight cast into the front of the vibration damper and a weight is welded onto the torque converter. I never learned if the 3.9L is internally or externally balanced. If your old and new vibration dampers look the same, there's a good chance both engines are balanced the same way. You'll have a constant vibration if you don't use the right torque converter.
Saturday, April 9th, 2011 AT 3:02 AM