What Is Spark Plug Indexing?

[@roberts1159]

Never knew indexed plugs existed. Thanks for educating us about this topic.

[@ford3961]

I often have to index the plugs on my domed-piston race car engines to ensure that the ground electrode does not contact the piston.

[@BubblesTheCat1]

This video didn't explain anything about how to index your spark plugs. Take a marking pen and mark the open side of the electrode. (on the ceramic part) Then tighten the plugs in such a way that the open side mostly faces the inlet valve. You might have to tighten some plugs slightly more or less than others, as long as you don't overtighten or undertighten any of them too much or too little. The crush washer should give you enough give to play with. I've always done it like this, and have never had a problem with too tight or too loose plugs. 😀