spark plugs
 

A not so honest indy replaced the plugs as part of diagnosing what turned out to be a fuel distributor issue. A week later the good indy gave me back the plugs, which had black deposits on the tips,etc. It seems a shame to throw them out. Can they be cleaned & made usable?

I do it all the time! I rarely replace plugs - just clean and regap. I've been doing it for over twenty years for all the cars I take care of with no ill effects on performance. I replace the plugs when the center electrode is worn too far. The money saved has added up over the years.

I clean plugs by grit blasting. Besides removing all the deposits, the key point is to clean the insulator nose around the center electrode. Deposits on the insulator can provide a leak path for the spark. Then I finish-clean the plug by wire-wheeling the threads and inspect around the insulator to make sure there is no leftover grit trapped inside.

Just a reminder - don't forget to put a thin coat of neversieze on the spark plug threads before installation.

Thanks.Good point about the antiseize. However, I'm lacking whatever tools are needed for grit blasting-is there any chemical cleaner, like wiping/brushing with acetone, which would work?

No, the porcelain really needs to get cleaned. And grit blasting is the only way. I sometimes wire brushed deposits from plugs during the leaded gas/12,000 mi tuneup days, but I don't think that's a good idea anymore.

I'm fortunate that I've always had a grit blaster at my disposal.

I've seen a tool made specifically for cleaning spark plugs. All you need is shop air. It's basically a hand held grit blast gun with a bag that recycles the abrasive. J C Whitney may have it.

You should never use a metal wire brush near the center electrode insulator. If its surface is not perfectly smooth, it will abrade the metal bristles, leaving a conductive track on the insulator. Many surfaces and all ceramics are harder than common metals, and will present this problem, particularly if they are supposed to be an insulator.

Steve