Timing chain replacement

Mine broke at 217,000 doing 75mph on I-94. That's really the only reason to change one on a 318 or 360. The only way it would make a noticeable difference in the way your truck runs is if your chain has jumped a tooth of something like that. My truck exactly the same as it did before the chain broke.

From a technical standpoint if your timing chain is worn it will retard the cam timing (less low end torque) and also the distributor should be reset so the injector timing is correct.

Any idea if a loose timing cahin would cause your timing to jump around ? When I look at my timing on a scanner it constantly jumps up and down : at idle all the way from 6.5 to 20 degrees and at highway speed (about 1900 rpm) from about 18.5 -30 degrees.