Indexing spark plugs

[seang]

Firstly, this is a well-documented practice easily turned up wth a Google search. Secondly, this might have more of an effect on a SOHC because a DOHC KA has centrally located plugs.

I tried this on my 134hp SOHC truck motor by swapping the plugs around until I found the ones that lined up without the need for indexing washers (one of them is a little off, but the open gap is still generally aimed into the center of the combustion chamber, so I feel okay running it). And the result is not a whole lot more power, but it seems to run smoother when it I peak it out, which is frequently. So that might add up to a few hp, but it was totally free to me. All I did was swap the plugs around until they lined up best, not perfect, but as good as they could be.

I think indexing the plugs increases efficiency by a percentage. For example, 2% of 300hp is larger than 2% of 150hp. But I read so much about people wanting to bolt on more power, more efficiency. This is one of those things people can do, and the only logical thing I can think of is that someone would discredit that it is only a few hp and not 30hp.

After reading, thinking, and finally doing, it seems to me that keeping a $20 set of indexing washers around is no more radical than keeping an extra jug of oil around in anticipation of the next change. And being cheap like I was, you can just get the plugs as good as they will naturally go, without indexing washers, as long as the gaps are not pointing directly at a wall.

[breadbox]

So You just draw a line on the outside and try it to go to 12 o clock?

[seang]

I used a permanent marker on the insulator to mark the position of the gaps. My plugs are cheap and copper, but this would work with single platinums nicely. Here are two of the articles I read:
http://www.fordmuscle.com/archives/2000/07/indexplugs/
http://www.hubgarage.com/mygarage/summi ... logs/10030
One article (the Ford one) says to position the gap towards the exhaust valve, and the hubgarage article says the intake valve. I think that the shape of the combustion chamber has everything to do with it, and there are alot of those, so it is hard to say in a general sense what position is best. The Ford article has two good comparison pics.

This picture is SOHC specific:


I tried to get the the gaps facing the center of the chambers, in the middle of the 3 valves and away from the wall.

[neverlift]

. I lost a few ponies(boosted) and a slight reduction in spool. I decided to start them 180* from last time, feels flat on the bottom.

dual cam..

[seang]

The DE has an advantage being that the spark plug gap is always facing an open area, so indexing them might be, dare I say, redundant. Side-gapped spark plugs might make a slight difference, but at the expense of plug life. It seems that the "straight down" orientation* of a side-gapped plug would work well with the bowl-shaped dish of the DE piston. But, then again, I don't hear DE owners complaining about their NGK's.

* What I meant by "straight down" orientation is that, with a side-gapped plug, the electrode is not shrouded by the ground strap when looking at it straight-on.

[neverlift]

I run bkr7e cost me under 10 bux for a tune up...