You pretty much described a lot of the signs and symptoms. The reason turning the dizzy doesn't help much (if at all) is 'cause the crankshaft and the cam are out of sync. With all the slack in the chain they ain't at TDC together anymore. Replace the timing chain set before something worse happens.

 

Take a straight edge, place on the slack side of the chain, push it in and measure perpendicular from the straight edge. If it's more than 1/2" stick a fork in it, it's done. Replace.

I didn't know my 302 timing chain was getting old until it sheared all the nylon capped aluminum gear teeth. The engine promptly bent it's exhaust valves. If this can happen to a lo-po '78 smog motor, I'd hate to think what a loose timing chain would do to a cool 351C!

Regards,

Dean T

 

how much slack is acceptable with a timing chain if any in a good timing and gear set.

None. Replace that worn out set with a Cloyes TrueRoller. They're about $65 from Summit, but you'll never need another one....

and yes, a wasted timing set might cause the problems you're experiencing

 

Yeap, everything they said above. Some years back I had one that got so slack it actually jumped a few teeth and wouldn't run. When the chain was installed the timing was about 20 degrees advanced too far. Over the years, I had kept advancing the timing to adjust for the slack not realizing it had been gradually retarding because of the chain streaching. Yeah, change it now and it will amaze you how much better your car will run.