cam timing

[EWRice]

The last year had been busy with Chrysler marine rebuilds. 3 of the 318s that I had built all had the same issue upon reassembly. Don't know if anybody knows or cares about this, but I thought I would share anyways.

When I install new cams and timing chains, I will almost always check cam timing. This has not been as crucial in recent (30) years as all engines seem to be near dead on with factory timing marks. But go back before 1973, and we run into issues. Three of the engines I built had forged cranks in them. Generally, these were hi performance parts. Back in the muscle car days, the factory would move the key for the timing gear back a few degrees to gain more top end power, sometimes at a cost to low end. In a car it is not noticable. In a boat that requires torque from idle to 4200, it can be. What I found was that the 2 engines with cast cranks were near dead on with factory settings. The 3 engines with forged cranks were all retarded 5 degrees. Of course I made notes in my manuals about this, and after talking to an old school engine machine shop, they confirmed what I found was normal.
Those having older engines rebuilt, make sure the shop doing it checks cam timing.

[Tranquilo]

This might explain why my timing marks "sound" off. The more accurate I get, the rougher it sounds.

I really want to tune it by ear once it runs consistently

[Fastjeff]

I doubt it. Ignition timing is another animal from cam timing, but I agree that a cam retarded 5 degrees will reduce mid-range torque--the torque a boat needs most of all. If you engine is 'unhappy' without some extra advance at idle, that usually means a vacuum leak, idle adjustment off, or some other problem.

In running stock Pontiacs at the drags, we retarded the cams up to 13 degrees to improve top end power.

Jeff