timeing is controled by a key way under the flywheel, if its off te keyway is bent, there is also timing marks on the crankshaft and cam gears. these need to be lined up on top dead center. be careful as not to set them 180 degrees off or the engine will backfire.
There will be a mark on both the crank gear and cam gear, these must point directly at each other (the marked teeth will mesh). On plastic cam gears, there are several marks; care must be taken to distinguish the correct timing mark from stray plastic casting marks.
The timing marks on a 3406E Cat engine are recognizable by the bumps formed on the cover of the engine. The cam gear is also an important component when lining up timing marks. If in doubt, it is always advisable to visit a car dealership whenever engine work is involved.