Spark Plug Indexing?

[OrLackThereof]

Anyone care to explain the process to me? I've heard it described before but that came off as nothing more than vague, mysterious, and cryptic. Anything I can do to squeeze a horse or two out of it once it's running again, I'm up for.

 

[90mustangGT]

Basically, all you do is get it so the electrode is pointing to the valves to unshrowd the spark. Since spark plugs' threads arn't uniform, and neither is the thread in the heads, you can try different spark plugs in different holes to make a match. Just point the electrode to a reference point on the socket, such as the S in Snap-on and your in there. Just takes a little time. I used to have spark plug indexing washers, but they were more trouble than they were worth.

 

[HISSIN50]

i think Mike (Mustang 5L5) had a decent thread on that a week or two ago.
another way to do it is to put a sharpie marker line on the plug.