ScottS

iTrader: (2)

I have not yet seen a pic of the combustion chamber. Anyone have one so I can see where to index the plugs to? Or where do you index yours to?

Garrick

I heard that it doesn't really make a difference for our Nissans. Have you ever done this before or are you doing it for the first time?

andrei3333

what does this mean ?

ScottS

iTrader: (2)

I have not done it to the Maxima before. I have done it to my Daytona. I have seen various numbers mentioned as far as increase in whp/torque. The percentage is small, 2% to 4%. None of those #s for our engines. To me it just makes sense that it would help. It would not hurt things. That makes it worth while to me to do when I swap plugs.

Indexing the spark plugs is having the opening of the plug pointing in the direction of the exhaust valve. The idea being this exposes the initial explosion to more of the mixture. Having it point at a wall, well, you could see how that could hinder propagation of the flame front.

If our plugs are in the center of the chamber, I could see way less of a reason to do it. If they are to the side, then I would do it. However, I have no idea what our combustion chamber looks like. Anyone??

accordingtou

iTrader: (41)

3.5 L
VERY SIMILAR TO THE 3.0L
Small port=exhaust

nismology

iTrader: (8)

Wouldn't it make more sense to have it facing the intake valves since that's where the a/f mixture is coming from?

ScottS

iTrader: (2)

Thank you very much for that Picture!!!! Still be cool to see one of the 3L. Looks like not much to gain.

Do not recall the reason for pointing towards the exhaust. It is something others have mentioned. A quick google has some people suggesting towards the squish pad.

http://www.fordmuscle.com/archives/2000/07/indexplugs/
http://dodgeram.info/Engine-Gas/Spar...0_indexing.htm

mevjen

you want it to burn towards the exhaust valve though. assuming facing it one way or the other would make it burn in one direction it would have to go towards the intake valve, hit the cylinder wall and then make a 180 to the exhaust valve. I have never heard of indexing though. sounds kinda pointless. they should make car engines like airplanes with two spark plugs for an even better burn.