You haven't mentioned if it's a 6 or a V-8. Either way, check to see if the distributor is rotating when you crank the engine. The 8 is much more likely to have valve timing problems, since it uses a timing chain instead of gears. The timing gears on a 6 either work, or they don't, as a failure usually involves a few teeth stripping, and the cam doesn't move at all. A V-8 will sometimes jump a few teeth, resulting in late cam and distributor timing. If it runs at all, it won't get out of its own way!
Jerry
