I have a 89 Chevy 305 TPI that burns through a distributor cap about every 2,000 miles
I am nowhere close to being a mechanic but I am minimally astute about
car problems and repairs. I have a 89 Chevy 305 TPI in my toyota
landcruiser. Over the past few years I have had to replace my distributor
cap about every 2000 miles. Each time I can see the burn mark on the
metal inside the cap. I have also replaced the distributor, ignition coil, spark
plugs and wiring in this time frame. I have also discussed moisture and
cracking with a few of the mechanics and there is no indication those are
the potential problems either. Each time I (or a mechanic) replace it I check
everything that I have already had replaced and look for indicators of what
else it can be. The only thing that continues to burn out on me is the
distributor cap. What am I missing?
Check your ground cables to the engine block, make sure they are clean and tight, you should also check you engine to frame and body grounds. Double check for the ground tab in the distributor cap. If it is missing it will run like it should but you will have the problem you described, don't forget to check the distributor harness also, a bad ground there can also have the same effect. HTH
....and use a MSD cap.
I suspect a worn out distributor bearing/bushing that is causing the shaft to wobble.