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sparkplug indexing

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Kansas Bad Man

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Non-VOC Member
Here is a tip that will increase the horse power of your Vin by one to two freebies. Well , it will cost the price of a couple of indexing washers from MORROSO sp? The drill is to point the open end of the ground electrode to the exhaust valve as near center as possible. This provides a wall that the incoming fuel /air has to go around , this prevents wetting of the plug and gives a lean mixture at the center electrode for an easer ignition. The indexing washers come in three different thickness to accomplish the drill, use only one washer, it helps to buy a box of four plugs, by selecting the plug and washer combination, you will come close to the wanted result.
 

davidd

Well Known and Active Forum Website User
VOC Member
Indexing washers are important, especially for those who are running very high compression pistons. Before you put the head on you should wind in a plug and make sure that its threads come up even with the hole threads. If it is short or long (protruding) those threads are a perfect area for over-heating. Make sure the high compression piston does not hit the plug and close the ground strap.

I have seen all sorts of position recommendations, but I think Max is right. On an engine with a carb and a mag I think pointing the open end towards the exhaust or the exhaust squish if you have some is good. I think there is some evidence to show that this will reduce the number of mis-fires. Some engines have shown a 1% gain in bhp., but the clearance issue and reducing mis-fires is important by itself.

If you are trying this with the head on, mark the open side with a felt pen and position it where you want it. My notes say that the 0.040" goes 105 degrees, 0.050" goes 210 degrees and 0.064 goes 315 degrees. Don't stack washers and make sure they are the flat washers, not the tapered ones.

http://www.summitracing.com/parts/mor-71910/overview/

David
 

Magnetoman

Well Known and Active Forum Website User
VOC Member
I have seen all sorts of position recommendations, ... Some engines have shown a 1% gain in bhp., ...
I first read about doing this a number of years ago, but it seems to me much more voodoo than it is science. As you say, all sorts of orientations of the electrodes are recommended as optimum, which is the first sign things may not be what they are believed to be.

And, no matter what, a purported gain of only 1% is very hard to have any confidence in. It means you would have to believe the dyno data was reliable to the nearest 0.1 h.p. for a number of runs, as well as all aspects of the engine itself being reproducible at that level. That is, you would have to be confident in the data and the reproducibility of all of the conditions such that your Vincent produced 50.0 h.p. with one plug orientation, 50.0 again to check reproducibility, 50.5 with another orientation, 50.0 again when returned to the original orientation as a check, 50.3 at another, and 50.0 again.

Although modern dyno outputs seem a lot better than old ones, much of that is because the output has been so heavily smoothed. For the same reason the display of a modern digital oscilloscope looks so much better than that of an analog unit. But that's because much of the interesting (and often important!) variations have been digitally removed for your viewing pleasure. Data from engine dynos are intrinsically noisy, which is why 1% strikes me as voodoo.

Maybe I haven't looked hard enough, but I haven't found any dyno manufacturer who even claims 1% accuracy and/or repeatability for their engine dynos. Chassis dynos are more problematic because each run everything in the entire system, from engine, gears, through chain, through wheel bearings, through the internal mechanics of the dyno heat up.

In a world where people pay a lot extra for large diameter, gold plated audio cables for their speakers because they think they sound better, it's not at all surprising that companies sell washers for a lot of money on the premise of a 1% gain. On the other hand, it's not as if those big speaker wires or indexing washers do any harm (except to someone's wallet).

Having said the above, in the case of very high compression engines where there is danger of the piston kissing the spark plug electrode, indexing can be essential. But to avoid mechanical interference, not to gain 1%.
 

Kansas Bad Man

Well Known and Active Forum Website User
Non-VOC Member
I ask your name and was told that was impolite , I WONT do that again magnetman, however you spoke with authority about the workings of a dyno and what could be expected from one. Do you own one, have you ever owned one, have you ever put any thing on one, car or motorcycle? You spoke of HP and how small tuning advice, is voodoo, and makes no difference in the plot of things. This brings me to my next questions, have you ever raced, have you ever set any speed records, have you ever been the tuner on any race team, What is the fastest timing slip you hold, if you have a record time of any kind please post and we will compare dyno notes and speed records where we did the tuning. The best I ever made was 573 HP with 180 ci of Vincent, the indexing of the 8 sparkplugs helped a bit, but we can talk about that after I hear some of your provable feats of making hp.
 

Magnetoman

Well Known and Active Forum Website User
VOC Member
You spoke of HP and how small tuning advice, is voodoo, and makes no difference in the plot of things...
No, that is not the case. I did not say 1% was not a worthwhile increase if it could be achieved.

What I said was 1% is a very small difference in h.p. to measure. I said the fact different people claim different orientations give 1% improvements, so there isn't even agreement on this crucial matter alone. That is, if some people say there is a 1% effect if the electrode is pointed in some specific directly, but there isn't agreement which direction that even is, it's voodoo science. I said I was unaware of any dyno manufacturer who claimed their unit was good to 1%. I said to be sure one actually was measuring a reproducible 1% effect given the reality of full throttle, run-to-run variations would require more precise data than I've seen dynos produce.

My comments were entirely about the implausibility of claims of measurements of h.p. to 1% in the necessary series of runs with plugs in different orientations (which, in fact, require ~5x better reproducibility than 1%, since one has to distinguish between, say, 50.5 h.p and 50.2 h.p. to know which position is best). My comments have nothing whatever to do with speed records or the highest h.p. you have achieve. They only have to do with the plausibility of reproducible measurements having been made of changes in h.p. at a level better than 1%.

However, if someone can point to published dyno data credibly showing this effect, I will gladly remove my skepticism about this.
 

vibrac

Well Known and Active Forum Website User
VOC Member
On a Vincent head like mine I have a question more pertinant than indexing the plug
Given the choice-(and with a twin plug head I have been) which is the best side to have a single plug, LH or RH? obviously the spare plug hole on a road bike is for a Royal Enfield decompressor much preferable to the mares nest of linkages roller and oil leaks in the timing chest.
 

Albervin

Well Known and Active Forum Website User
VOC Member
I ask your name and was told that was impolite , I WONT do that again magnetman, however you spoke with authority about the workings of a dyno and what could be expected from one. Do you own one, have you ever owned one, have you ever put any thing on one, car or motorcycle? You spoke of HP and how small tuning advice, is voodoo, and makes no difference in the plot of things. This brings me to my next questions, have you ever raced, have you ever set any speed records, have you ever been the tuner on any race team, What is the fastest timing slip you hold, if you have a record time of any kind please post and we will compare dyno notes and speed records where we did the tuning. The best I ever made was 573 HP with 180 ci of Vincent, the indexing of the 8 sparkplugs helped a bit, but we can talk about that after I hear some of your provable feats of making hp.
Max. I think it is impolite to start, what is called in the vernacular, a pissing contest. Magnetoman has used non confrontational, statistical and methodical reasoning in his answer. You took it as a sleight that I am sure was not intended. People like Bill Thomas, Davidd, Vibrac and others could agree or disagree with you based on their experiences but Magnetoman uses science, facts and statistics which, while many consider boring and pointless, I consider to be fact until proven otherwise.
573 horses is a LOT of power from 3 litres of OHV 1940s technology. I hope everything runs in your favour this year and you get the results for which you have worked so hard. Russell Wright told me once that he got lucky when he set the LSR; preparation, checking, double checking and hope nothing goes wrong. He always was a modest chap.
 

bmetcalf

Well Known and Active Forum Website User
VOC Member
We all know how approximate a vernier caliper is; I think dynos are in the same category. We just don't have a micrometer-equivalent dyno to use.
 
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