Indexing plugs
 

OK, I have several of my fellow racers that index their plugs. It is about half and half on which way they do it. When you index a plug, do you put the spark plug gap pointing down to the piston or up toward the valve springs. I thought I was doing it right but now I am second guessing myself after finding about a 50 50 split among other people.

I thought you pointed it toward the exhaust valve. :? to direct the flame or something like that...I don't fool with it so long as it don't hit the piston.

All of mine are indexed with the gap pointing towards the intake valve.

I thought the reason for indexing the plugs was to make sure the gap is facing down so if the piston hits the plug it don't close the gap. (right)

This is always what I've done and the engine builders (nyes,apd) have done also. Between 10-2

If the piston hits the plug on a blower motor, you've got bigger issues at hand than worrying about closing up the plug. :shock:

I do it that way only to ensure consistency between cylinders. Honestly, with 23+:1 compression while in boost, I dont think it matters much.

has anyone tested this on a dyno?

I just stick'em in .

http://www.eatonbalancing.com/blog/2...plug-indexing/

Granted, they're talking about Ford engines, but it's still a decent article.

If you use a plug with a crush washer, you can mark the ground strap or gap side of the plug (depending on which you want to see), and then tighten it, crushing the washer until the mark lines up where you want it.

If you have a taper seat plug, using tapered seat indexing washers will be required.

http://www.summitracing.com/parts/MO...0/?image=large

What is the correct method?

The old timer that taught me always had me index the plugs and point the gap toward the intake valve. I have done that on N/A & Blower motors.

Is this incorrect amoung the world of engine builders out there?

I am having a hard time swollowing the part about just in cast the piston hits the plug. :?

I by no means am a rocket scientist, but if I have always used clay to check my valve to piston clearance and that also gives me a guide to the distance between the spark plug and piston. Even though math calculations seem to be correct, I have always check my clearances this way. "Just my little bit of self assurance"....

By the way that was an interesting read OneBad.

I have to index my plugs because they will hit and index all of them between 10 and 2 o'clock .
I mark the plug with a sharpie straight down the plug from the strap so i can see where it is and add or subtract washers until they all line up.