Having had experience with both timing belts and timing chains, a few observations: chain failure, especially double row chains, is usually gradual and signaled by the clatter of disintegrating links. My guess that single row chains would furnish only seconds of warning. A double row chain is akin to two bicycle chains side by side with three rather than four rows of link plates. A single row chain is just like a bicycle chain.

Belt failure is usually silent and sudden. I doubt that oil on a belt would cause more rapid failure; synthetic rubbers are pretty robust. Whether or not failure of either belt or chain "destroys" the engine is independent of the method of cam drive, but rather the design of the engine, i.e., whether the rising piston would contact a valve left open by the cam drive failure. That is to say, is it an "interference" engine, or not. As examples, my friend had a Fiat 1600 DOHC belt driven engine on which the timing belt broke while he was starting the engine. The result: 4 of the 8 valves bent. My Datsun 510 1600 SOHC engine suffered the cam drive cog falling off the cam shaft while the engine was running. No damage. The former had an interference engine, the latter, not.

AFAIK many modern engines are "interference" since that offers better power and economy. Whether they have cam belt or chain drives follow the manufacturers' recommendations for replacement/maintenance.

Re LXDude's post, after the problem with my Datsun, the car had no power after my mechanic massaged it. I determined that the VALVE TIMING was off by a tooth or two and fixed it. Back to proper engine response. Valve timing rarely has to be adjusted unless the belt/chain has to be replaced, or the chain stretches a bit. Engines commonly have a provision for compensating for this stretch, which usually occurs only in high mileage examples.

BTW, ignition timing was/is set in distributor engines by rotating the distributor a few degrees while observing with a strobe light a mark on the crank pulley. Setting the points gap makes a VERY small difference in ignition timing; that adustment is referred to as setting the dwell.

What this digression has to do with film I don't know, but its been fun!