Hey just wondering how long before you have to change the Spark Plugs and Distributor Cap? I got my car about a year and one month ago and I never change the wires and the Distributor Cap. I did replace the spark plugs and oil during the time I got the car. Anyways, if is time to change them let me know which are the best Wire, Distributor Cap, and Spark Plugs to get for my 81 FB 12A Stock.

While cleaning the Distributor Cap I have notices the rotor had some little stuff built up on the edge of the metal parts that spin and the parts that have the spark plug wire on the Distributor Cap. Could this be what is making my Engine run weir?

 

The crusty build up is normal and can be scraped off.The cap and rotor should be done about every 20K miles,although they arent very expensive and replacing them more often simply cant hurt.
The plugs will wear at different rates depending on ignition setup and driving habits.My stock NGKs would only last 5K miles with an MSD direct fire setup.The stock ignition and a stock engine will usually net you about 10-15K miles, roughly.The plugs will still fire,but performance tapers off as the plug gap erodes.
For the record,I had much more plug life when running the Denso plugs #W25EDR14

 

Running a 6AL on the leading, Blaster2 coils, and B9EGV's, I get about 8000 miles out of my cap. I get HUGE grooves at the terminals, not just corrosion) a bit less from the plugs (running 15 degrees BTDC leading and 5 degrees BTDC trialing)

 

Would that corrusion make my engine act weir during idle and during deceleration from 2K to 1K?

 

Are you talking about that weird lugging sensation that rotaries get below 2k? It's fairly normal.