Who here index their spark plugs?
 

Not sure if indexing plugs makes a difference in a hemi, but I'm planning on doing this since I have the heads off. This way, I can acurately position the plug tip using washers and then take note of which goes where. I'll remove the plugs to make turning the crank (timming, valve adj, etc...) easier. Then when ready, reposition the plugs in the proper orientation.

Years ago, I read a test that kinda rained on that parade.....

I index my spark plugs on my personal watercraft ( Yamaha GPR1300R) and my dirt bike(Honda CR250R) but they are both 2 strokes and it does seem the make them both run cleaner and rev higher. I have never tried it on a 4 stroke motor. On a two stroke, you want to index the open end of the electrode away from the intake charge or towards the exhaust port. I see several speed merchants sell the indexing washers and I can't believe they are all for 2 strokes. Maybe it does work on 4 stroke engines as well.

Some say that you loose 1-2% of engine power if the gap is facing say the chamber wall vs. the center or towards the valves.
Small amount, but every bit helps. At minimum, you'll have a more efficient engine and improved economy.

There's a toss up between facing the exhaust or intake valves. So I just make sure it's facing the center.

I used to index my plugs on my -4 cylinder 914 motor.
but don't bother on the -6.

you don't have to pull your heads.
just take a felt tip marker and put a mark on the plug in the direction that the electrode points. Then after putting the plug in you can look and tell which way its facing and use the different thickness' of washers to adjust.

brant

If I had my heads off, I would do it. It would be tough on my 3.3 to do it in the car. It sure can't hurt and like you said, every bit helps.

Thread here...

http://forums.pelicanparts.com/porsche-911-technical-forum/250316-who-here-index-their-spark-plugs.html

By adding washers, are you not backing the plug out of the chamber slightly?
Not sure whether or not this is a factor, but we are talking about a small gain/loss here.