Talk Morgan Forums Community Vehicle Talk (non-Morgan) Indexing Spark Plugs

This is a new idea to me but on the US Healey boys forum it seems common practice. The idea is to align the plug by using copper washers so that the spark area is centred in the cylinder and not facing the cylinder wall. Numbering the plugs once done, anyone had a go at this?

They also file the tip back to the edge of the electrode..

heres a bit more about it...

http://www.enginelabs.com/news/getting-the-most-out-of-your-ignition-spark-plug-indexing-101/

I am very surprised if that adds anything at all to the power given a 4 stroke where the stochimetric mix is sucked in & then compressed before the spark ignites it.

Hmm, sounds like a solution in search of a problem to me. Although I can see the logic, I'd be surprised if any actual horsepower benefits were actually measurable, they'd probably be within the standard variance of the dyno.

But that's largely irrelevant, if you fancy having a go and feel that it brings a subjective benefit, then it's worth doing!

Very common practice on dragster engines, I once worked at a dealership with the crew chief for a UK team and he had a box of assorted thickness shims in his kit and I asked what they were for. he said its all about flame spread and alignment of the electrode spark in the most efficient segment of the combustion chamber, I started yawning after that.

Apparently also used for those at the extreme end of concourse in some countries who want the names on spark plugs aligned. (and yes the judges also check the plug torque to see if anyone's cheating... I would have them all wrapped in neoprene ;-))

The judges or the spark plugs?

The article below is taken from the NGK spark Plugs site, they think it has minimal advantages.

"Gapping and Indexing

Gapping

Since the gap size has a direct effect on the spark plug's tip temperature and on the voltage necessary to ionize (light) the air-fuel mixture, careful attention is required. While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap setting (to ensure ignitability in these denser air-fuel mixtures). As a rule, the more power you are making, the smaller the gap you will need.

A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air-fuel mixture maximizes burn efficiency. It is for this reason that most racers add high-power ignition systems. The added power allows them to open the gap, yet still provide a strong spark.

With this in mind, many think the larger the gap, the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think.

Indexing
   
This is for racers only! Indexing refers to a process whereby auxiliary washers of varying thickness are placed under the spark plug's shoulder so that when the spark plug is tightened, the gap will point in the desired direction.

However, without running an engine on a dyno, it is impossible to gauge which type of indexing works best in your engine. While most engines like the spark plug's gap open to the intake valve, there are still other combinations that make more power with the gap pointed toward the exhaust valve.

In any case, engines with indexed spark plugs will typically make only a few more horsepower, typically less than 1% of total engine output. For a 500 hp engine, you'd be lucky to get 5 hp. While there are exceptions, the bottom line is that without a dyno, gauging success will be difficult"

The competitors!

You need to get out more, chum..

Talking of which, is there any appetite (ho ho) for a Saturday lunchtime visit to the Greedy Goose?