I hope someone can help me with this!!?? I have what I think is a 1973 460, it has been rebuilt and punched .030" and the guy that I bought it from tells me that he put a "mild" cam in it but didnt remember the specs. Anyway, I had to pull the engine to repair a leaking rear main seal and thought it would be the perfect time to install a "straight up" timing chain and flow kooler water pump. What my problem is: I didnt notice much power difference with the chain (it did have the retarded cam gear), and it regularly overheats!? With the vacuum advance connected it idles at 30 deg. BTDC, when disconnected the engine wouldnt run. Well, I disconnected the vacuum advance and adjusted the carburetor so it would run and set the timing at 12 deg. BTDC. (I'm in Colorado @6000 ft.) When I reconnect the vacuum advance it advances past 30 deg.BTDC. The mechanical advance appears to be working so I disconnected and plugged the vacuum advance and set my initial timing at 18 deg.BTDC. (the engine idles much better if I advance it farther but I am batteling overheating). What I am wondering is does the timing chain affect the ignition timing? It seems like the marks on the balancer are out of whack with pointer. This engine is in a truck and used exclusivly for towing HEAVY loads at high altitudes. I am VERY sorry for being so long winded, but I am at wits end. Anyone have any pointers??

 

The dist runs directly off the cam. Changes in cam advance have a direct effect on rotor position in the distributor. Set your initial timing to about 8 deg BTDC and reconnect the vacuum advance. At your altitude you should not have any problems with ping even on regular fuel unless you have more compression than stock.

The vacuum advance is supposed to advance the timing at idle and part throttle (the periods of highest intake vacuum). When you slam the throttle all the way open at idle it kills vacuum, which kills the advance. As the revs rise the mechanical advance takes over.

Engines can be real picky about timing. Low compression engines like a lot of advance at low RPM with a modest mechanical advance curve and relatively less overall advance. High compression engines tend to respond better to less initial advance but more overall advance. If you are running the factory dist, it might not be a bad idea to have a good tuner rebuilt your dizzy to take advantage of the different cam gear setup. Its inexpensive and will make sure your dizzy is in top shape.

Brad

 

Thanks Brad, Do you think that my timing is contributing to my heat problems? I have stock heads, I'm pretty sure that the compression is pretty low. It seems like my overheating problems started after the chain & water pump change.

 

Probably. If your timing is off it can cause heating issues. You might also make sure that you do not have a water hose that is collapsed internally.

Brad