Is there a way--------

[Coyote]

to bench test spark plugs? I have about 20 lying around. Some are good an some are not. I know how to test them on a motor, but thats a long time running with no plug in the hole.

[djfisher22]

http://www.youtube.com/watch?v=l5v1XVSCY-U" onclick="window.open(this.href);return false;

[Suzsmokeyallan]

Spark plugs are finicky, especially used ones. They may look ok on a visual spark test, but when actually fitted into an engine under load, don't work as they should.
Chris I'd suggest you take the time to "engine test" those used ones you have and date them, or just toss them out.

[Cliff]

I agree, toss them and buy one set of new ones.

[Fritz500]

I agree, toss them and buy one set of new ones.

Place the used plug gently on the surface of a pond. If it floats then it is suitable for re-use. Works for me every time.

[jabcb]

They used to use the same test for witches.

[H2RICK]

Champion used to sell a bench-top plug tester but I haven't seen one in 40+ years.
As Allan says, they may work fine in an atmospheric test but once you put them into actual operation at 150 PSI compression, it's another story entirely.
New plugs are cheap enough so why not bin the whole lot.....assuming they're conventional plugs.
If, however, they're gold palladiums or other precious metal electrode-style plugs then I'd be testing them, for sure.