Talked to an old racer today who raced porsches and VWs in the '60's. Told me I should consider "indexing" my plugs for better performance. He explained what "indexing" meant, and while I have a basic understanding of what he was talking about, I do not think I could accurately repeat his description here. Does anyone else know what "indexing" is and whether this would matter or help with our cars?

Len

 

"Old Racer" here.
Indexing was done on other motors as well. It was easy when plugs had crush washers. Taper plugs make it more of a pain. With older head designs it was more effective.
I really wouldn't bother.

 

A matter of drawing a line on the porcelain of the plug that lines up with the electrode. You can screw the plug into the hole with the electrode pointed in the best direction for optimum flame travel (not sure what that direction is on a Mini). The line allows you to see where the electrode is in relation to the combustion chamber. As Obehave said, you can use washers to get the alignment right, but it's time consuming. We did this on my Spitfire when it was a GP car to keep the piston from hitting the plugs (15:1 compression). Now we continue to do it for whatever power gain there is(not much) even though it's only 11:1.

On a street car, don't bother.

 

Indexing is maybe worthwhile, if you're looking to extract the last possible erg from your engine.

If you've already done the hourly check of the pressure on your nitrogen filled tires, removed your antenna, antenna base, mirrors, and windshield wipers for cleaner aerodynamics, taped over the foglight ports in the bumper and the seams for the hatch, passenger door and sunroof, it might be worth going after the final minutiae like indexing spark plugs.

But probably not.

 

Indexing also kind of goes out the window when you have four prong plugs...

 

And 4 valve hemi..

 

Just to clear this up a bit.

If you have the original 4 electrode Bosch plugs indexing isn't nessasary or possible. If you have switched to a single electrode plug, like denso or NGK, then you can.

Take a marker, not a pencil, and mark on the top of the plug where the plug gap is pointing. Install the plug. Once the plug is in. Check to see that the gap is pointed towards the intake valve. If it is not you can take the plug out and try it on a different cylinder until it does. There are 2 ways to do this. 1) Buy a bunch of plugs and keep trying different ones until you get all four lined up, or 2) Buy some indexing washers. They come as a set and usually have 3 different thicknesses. Try different washers until the gap is pointed at the intake valve. The idea is to not have the electrode blocking the spark from the incoming fuel/air mixture. This allows for a more complete burn.

I've done this for years and would compare it to installing a K&N drop-in filter. On some cars there is a measurable difference and others there isn't. For me, it's more about knowing that I've done everything possible to get the most out of the motor. I indexed my plugs (Denso Iridiums) when I took out the factory plugs and definetly felt a difference, not so much in power output, but smoothness in the upper end of the RPM range.

If you are an autocrosser, especially in stock class, it's not a bad idea since there are only a few mods allowed and races are often won by factions of a second.

My $.02

 

Good post I haven't done this since my drag racing days, where fraction of seconds do count. Of course we would also do other things to throw racers off...like the negative ion charger -- Johan