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Spark plugs


John McFarlane
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John, what vintage sparkplugs are you talking about. If they are relatively new, you can bead blast them clean. If they are older plugs you should soak them in a good cleaner, like kerosene and then brush the gunk off with a stiff bristle or brass bristle brush. Do not blast them if you want to use them again. That will blast the glazing off of the electode and effectively prevent them from operating properly. Without the glazing they will carbon up more rapidly and there goes your spark.

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Heavy duty caustic soda carb cleaner is by far the best, after a hot water rinse they are almost new. The porcelin comes out so nice you might think they were new.

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I cannot give an exact date. The glazing was applied to the electrodes to keep them from fouling due to improper fuel-air mixture - back in the good old days of carbs and coils. When FA mixture and ignition became computer controlled and the possibility of flooding along with other mixture/ignition problems diminshed sssspark plug manufacturers were able to eliminate the glazing process thus saving costs. I would guess this would be in the late-70s or early-80s. <P>Maybe Terry will come on with a better answer. He is much more of a spark plug expert than I am. blush.gif" border="0

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Gee Ron, just cause I've got about 2000 in my collection doesn't make me an expert, but I have explored a little history and can give my very non-technical opinion on the subject. Actually, the very earliest plugs were made using French clay as the ceramic. Mica was also a popular insulating material (thin mica washers layered together). In the early days, the glazing was necessary to protect the porous and brittle ceramic. In 1916, Champion began using a mineral called Siliminite (not in my spell-check). They acquired the sole rights to mine this material when they purchased a competitor plug maker (Jeffrey DeWitt). Siliminite is so hard that a broken piece of it will cut glass. Its been the material of choice for many years and glazing over it is not really necessary. I am not sure what other plug makers use for their insulating material but any post war major brand plug should be able to withstand blasting to clean the junk. Fine sand and low pressure of course! My personal preference however is to use the carb cleaner. I just feel better using it as Im always worried about something getting stuck way up inside the plug, then letting go into the engine later. Ive also seen folks just hold the business end of a plug up against a wire wheel and the result is a discolored ceramic, but no other significant damage. <P>As for a blasted insulator facilitating the "regrowth" of the gunk accumulation, I hope our mechanics are smart enough to know that clean spark plugs are not a permanent cure for bad rings, etc.<P>Funny thing about plugs, nobody every throws them away. We always "save" them for some strange reason. <P>Now, does anyone out there have any old plugs available? (Please, not the four legged kind). <P>Terry

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I've used the carb cleaner and stiff brush method for years, augmented with a dental pick to get at specific areas. smile.gif" border="0<P>Terry, I always throw out used spark plugs. But what should I do with the Edison plugs in original boxes and wax wrappers that are the wrong tip length for my car? confused.gif" border="0<p>[ 02-05-2002: Message edited by: ted schneider ]

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I have a specialized spark plug cleaner that I bought from Harbor Freight Tools for about $19. It's a small sand blaster that only blasts the electrode end of the plug. It seems to work very well.<P>This is not a new idea, by the way. In my grandfather's garage there's a 1940's Auto-Lite version of the same thing. They both have a rubber ring that the plug fits through. Inside the tool a blast stream is aimed at the electrode. Manipulating the plug while blasting cleans <I>any</I> accumulated carbon in a few seconds.

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After reading Dave's post I went out in the garage and rummaged through some boxes of 'junque' Dad has kept forever. In it is a 'portable' spark plug cleaner. It is a black plastic box, with a switch for 6/12V and two small jumper cable type connectors on it. Seems it runs off the battery, it has a sand like grit in it, and a rubber gasket up top. Not sure how exactly it works I didn't try it out, I had forgotten about it. It has to be over 30 years old, I can remember when he bought it and I was rather young. I think it may have been a J. C. Whitney purchase, I have some relative (cousin of some sort in my parents generation) that worked for them, many of our parts and tools came from J. C. Whitney back then.<P>I've just always used the carburetor cleaner, and if need be an old tooth brush to clean plugs with. Guess I am old fashioned and like doing things the hard way it seems...<P>Rich

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Dave ~ I got my spark plug sandblaster from J.C. Whitney at least 40 years ago and am still using it. It's pretty much what they have at Harbor Freight. <P>As far back as '49 I had a summer job where the owner of the shop had one. That is what caused me to buy one like it in the early '60s. I know that type of small, air powered, sandblast cleaning unit goes back at least to WW II. I imaging the unit was developed as an inexpensive and portable substitute for the large bench units of the '30s. ~ hvs

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Thanks for all the information. Though one thing haunts me. When I was training as an auto electrician in the mid 70's, the oldtimer who was THE MAN told me never to clean plugs with any sort of wire brush. It leaves tiny remnants of steel/iron/brass which leads to premature failure of the plug due to decreased insulation resistance. I suppose this may still be the case, but not in modern engines where plugs are easy to get, and usually a fair bit cheaper. Any thoughts on this ????

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If I might add, during my graduation year in high school my auto teacher had an old Champion spark plug testor that was used mainly for demonstration. <P>It allowed one to screw in a plug and vary the voltage/amperage going to the plug and was connected to the shop air supply so you could see the effects of pressure on the spark. It plugged into a wall socket so I guess the spark was at 60 hertz with variable voltage and pressure was adjustable from 0 psi up to 200 psi.<P>The really interesting thing about this device that made a lasting impression on me was how any pressure above 100 psi basically snuffed out the spark and the gap of the plug was very important and was related to electrode diameter.<P>I played with this device a lot and learned a lot about the dynamics of the spark kernel under various pressures. I tried a number of different things in this chamber one of which was the "v" electrode shape, the "y" shaped top electrode and numerous porcupine shapes. No, I did't get any royalty checks from the plug manufacturers for my discoveries either.<P>The interesting thing about all these shapes was how well they achieved good spark kernels at low pressures (due mainly to the number of sharp edges). And if you are wondering, the spark goes to the point of lowest resistance-always, not like the rotating dancing spark you see in the commercials <P>The other discovery I made was how easily the spark was snuffed out at the higher pressures regular plugs easily handled. I don't use these fancy plugs in my high compression race engines because of these findings. Many thanks to my old auto shop teacher (may he rest in peace).<P>The other thing I tried was the old wire wheel cleaning trick, my auto shop teacher would slap your hand if he caught you doing this to a plug. I was determined to prove him wrong. I tried brass, stainless, stiff bristle horsehair as well as one made out of baling twine that we used to clean pistons.<P>Guess what, the old guy was right. Any metal brush would embed enough metal particles to short the plug. The plug would still fire but it would be weak and you could watch the current trail go down the insulator and short to the shell. The other brushes had no effect, but they didn't clean all that well either.<P>I've read that crushed almond or walnut shells is what is recommended in old aircraft manuals but can't say I've tried them. The baling twine works great for cleaning ring grooves and won't remove any metal during the process and is the recommended technique in old Lycoming engine rebuild books. Some later manuals say to use the nut shells as it works faster.<P>Glass beads are a big no-no as the beads shatter and the tiny bits end up embedded in the soft aluminum, ring life is greatly reduced if this is done and no amount of ring lapping will get the particles out. The pistons are scrap afterward.<P>One last thing I will share, the only spark plug trick that worked well enough for me to still use it to this day. It's an old hot rodders trick that you have probably heard/read about before. <P>Grind away enough of the top electrode to expose half of the center electrode. This works under high compression and doesn't wear like those "v" shapes either, the spark kernel ends up with greater exposure to the mixture and it won't overheat under the pressures of racing. <P>Some engines I've built (particularly the large bore wedges) will only run with this type of plug, I believe the high compression and large valve overlaps combined with the richer mixtures conspire to flood out the plug and I find this shape will "clear out" where others trap a drop of liquid fuel in between the top electrode and the center electrode. Works best with alky fuels motors and might be the only way to get these motors to idle reliably in some instances.<P>Sorry if this is out of context but I thought it appropriate for this thread. wink.gif" border="0

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In an earlier post I mentioned the possibility of damaging the electrode glazing with the sand blast/bead blast technique of cleaning. It shortened the life of the older type of plugs.<P>If that is true, why were the sand blast cleaners so prevalent? I also have a couple of the large garage style units in my collection. The answer is that they were popular because the shop could sell more plugs when the "cleaned" plugs broke down. blush.gif" border="0 <P>I still prefer the brass wire brush and solvent method on the older plugs. wink.gif" border="0

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  • 2 weeks later...
grin.gif" border="0 Chuck, I don't think you were out of context. You have an excellent knowledge of mechanical things. But, I, like most of the others on this thread , like the solvent method of cleaning spark plugs. I use carb cleaner or mineral spirits and a non metallic brush. Then, I file the center electrode just enough to get a flat surface and reset the gap to the vecicle manufacturer's specs. Of course, it's better to put in new plugs if you have them. rolleyes.gif" border="0
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Chuck,<BR>When I was studying tuneup I was told that for a spark to jump across the plug electrodes the fuel-air mixture had to ionize in order for the electrical current to jump across the gap. Do you suppose that in the Champion pressure tester you mentioned that the spark blew out because there was no fuel-air mixture. I too have noticed the spark blow out and have always figured it was because of no fuel.

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I know than in some high power radar applications the wave guides are pressurized. One reason is to keep them from arcing. The when you pressurize the wave guides you can run more power in them before they arc over.<P>In the case of the spark plug, you want it to arc over. And you want it to be under pressure (good compression). One way to get it to arc is to put the two electrodes close together. The other way is to increase the voltage. Since there are limits to the maximum voltage you can achieve with a single coil and point type ignition, your choices are limited.

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Interesting point BV, ionization is required for a spark to jump a gap. During my testing/playing I tried water vapor injection through a pitot tube I had rigged to the shop air inlet. I was afraid a fuel/air mixture would ignite and destroy the apparatus/me.<P>The only effect I noticed was that the spark formed a stronger more concentrated kernel and was harder to extinguish at high pressures, I think it took another 15 pds of pressure to kill the spark. Can't be sure if gasoline would lessen the effect or raise it.<P>One thing was apparent was any suspensoid increased the conductivity of the mixture which allowed the spark kernel to concentrate more effectively. <P>For a young high schooler I sure learned the effects pressure had on ionization. The machine itself did not build pressure and hold it, it merely admitted more shop air in. <P>I guess it was designed to as closely duplicate effects in a real combustion chamber without costing a fortune. It was apparent that higher pressures meant more turbulence. <P>The device itself was made by Champion and looked like it was supposed to be a display piece in a parts store or something like that. I guess to show how bad your old plugs were compared to your new CHAMPIONS-whatever.<P>It certainly was not a one off piece and I quite surprised no one else has mentioned seeing one somewhere else.<P>As far as ionization goes increased pressure should reduce the resistance of the working fluid but turbulence of the same velocity all things considered equal should have more effect at the higher pressure--more molecules moving right?!<P>Another thing I played around with was plug indexing and contrary to what you may have read the plugs open face should point into the prevailing mixture flow to prevent the side electrode from creating turbulence in the ionization zone. <P>I think of it like this, try lighting a Bic lighter with your back to the wind--the turbulent air swirling will blow it out. Now light it close to your chest facing the wind and the lighter will stay lit because of less air turbulence. <P>Laminar flow is important to the stability of the flame/spark mainly because conduction from molecule to molecule is steady and orderly rather than mixed and random.<P>I'm sure that these theories are covered under some SAE paper somewhere but I would have to pay for them. If any of you still have access to this kind of information through your school take advantage while you can. Here's a link to the Sae site;<BR> <A HREF="http://www.sae.org/products/papers/paprinfo/individu.htm" TARGET=_blank>http://www.sae.org/products/papers/paprinfo/individu.htm</A> <P>I could be all full of s___ on this but teachers I had didn't have a clue either, Engineering or Mechanics. I formed these ideas working on old cars trying to make them go faster, and the stopwatch was the judge. <P>The plug indexing thing didn't really have much role in my tuning until I started playing with methanol engines where the much richer mixtures played all kinds of havoc with the spark. <P>This was before aftermarket electronic ignitions were good enough and cheap enough for the average guy to afford. Now they have individual coils for each plug now and even the lowliest car has a great ignition system. <P>I once built a methanol burning 289 that had eight coils strapped to the intake, looked stupid and I didn't know enough about electricity to make it work right but I gave it a shot and learned a lot. <P>We had a really good auto wrecker here that used to let us dumb kids take whatever would fit in our pockets, I learned to wear a belt-Ha Ha Ha!!! That same wrecking yard checks my toolbox now whenever I go through like I might actually fit an engine in there, how times have changed.<P>As usual I've strayed from the topic and I'll probably get another "unregistered user" remark but what the hell!<P>Have fun and don't believe everything you read or hear, proving the other guy wrong is the best part. Especially when the checker flag is the one who decides!

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I agree, my main point was that metal brushes leave metal particles embedded in the porcelin which will short the plug. I clean plugs in carb cleaner too, old snowmobiles are notorious for fouling plugs.

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  • 1 year later...

I realize that this is a way old thread but I was trying to research some old plugs that I have had laying around for about 35 years and I ran across this thread and got hooked! smile.gif Obviously, I am a newbie to this site but felt compelled to register and add my $.02 worth to this old discussion!

Terry, obviously, I can relate to not throwing away spark plugs...to a point! I do throw away most used ones as I will explain in a minute. I wasn't sure if your "collection" was something that you pursue actively or was the result of being a pack rat. Either way, if you are interested, I will be listing some vintage plugs on ebay later today that might be of interest. I have a couple of boxes of 10 each Autolite racing plugs from the late 60's that have side electrodes. No, I'm not talking about what I have found in my search where the center electrode is shorter than standard and extends no further than the center of the center electrode. These have a hole in the side of the threads and the ground electrode is a pin that is perpendicular to the center electrode. There is a special tool to set the gap that I also have - along with feeler gauges with different size "wires" for setting the correct gap. I'd have to look but, as I recall, the tool and gauges were made (or sold through) Champion.

cridley, I know all about the Champion plug cleaner and tester that you described. My dad, his family and three of my four brothers are/were mechanics. My dad had one of those Champion units that I, too, used rather extensively to test plugs. At the time (mid to late '60's), I had a '64 Corvette that I had rebuilt and "worked" the engine from its factory rating of 365HP to about 425 to 450HP (based on the then current BHP ratings. Anyway, with 12.5:1 compession pistons, spark plug condition was a key to performance. The lessons that I learned from that Champion machine were invaluable and unforgotten since. Admittedly, I was not as creative as you were - I didn't add a pitot tube or anything like that. To add to your sescription of the unit, the air pressure was regulated and had a gauge to indicate how much pressure was in the "combustion chamber". What I found was that it was nearly impossible to clean, gap, file, bend, twist, or anything else a used plug and still get the same performance on that tester as a comparable new plug. There was some "breakdown" of a plugs performance over time that began and was noticeable and measurable (based on the tester) right from the start! Suffice it say, I became very anal about changing plugs in that car - usually every couple of thousand miles (it didn't hurt that I worked in an auto parts store!) for street use (it was my everyday - read only - car) and when at the track, I changed plugs after every run - time permitting.

One last thing, Champion also sold another tool back then that I have found to be indespensible through the years. The part number was CT-436 (as I recall) and they haven't been available for many years. It is a plug/ignition tester. Yes, there are/were other testers with neon bulbs to indicate when a plug was or wasn't firing but most of the others had a probe to poke the plug wire that caused problems of its own with the insulation. This Champion tester was about the size of a pen and even had a clip to keep in your pocket. The end was contoured to lay over the outside of the plug (or coil) wire and is one of the handiest little tools that I have ever had. I LOVE IT!

I don't think you strayed from the topic - I obviously enjoyed reading through this thread. I hope you don't consider this another "unregistered user" remark! My wife is asking if I have written my usual "book" yet so I will end. Thanks...

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Thanks for bring this topic back to life - it's fascinating from all viewpoints whether you collect the early turn-of-century stuff like I do, or are looking for the right item to run in a race car. Your Autolites are probably of more interest from a user's view than a collector. The main object of collecting seems to be acquisition of as many different brand names as possible. The Spark Plug Collectors of America has documented around 5000 names, so that's the goal if you want to pursue it. The first 100 are fairly easy, but then it gets difficult and much more expensive. There were so many privately branded plugs produced over the years that a lot were distributed only in small quantities within a small area. That makes it difficult to ever get to that magic number - but nobody well ever have them all as more are being discovered all the time. There isn't much new either - air gaps, multiple electrodes, side electrodes, shielded tips, etc-it's all been tried before. Even those spark intensifiers that cause the spark to jump a little air gap date back to the early 1900s. Its interesting to see them on ebay. Gotta be pretty confusing to someone who one day sees a plug not get any bids, then another sells for hundreds of dollars. An experienced collector who knows other collectors and their collections will be able to spot a rarity, but the casual observer can't often see the difference. It's a highly specialized area of collecting that I've pursued for 30 some years. The best part of it is sharing with others, in fact I'm going to take a couple of displays to a Boy Scout meeting on Monday evening and give a talk. Good luck on ebay w/your plugs. You might want to take a look at a website put up by a friend of mine, Steve Blancard. There is a discussion section there about plugs. Check www.1bigred.com/blancard

Terry

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This topic has been pretty well covered but on the subject of spark plug cleaners, we should consider the unit Champion marketed early in the century. This unit consisted of a glass tube, open at one end and filled with pointed pieces of metal. You filled the tube with gasoline (!), sealed the end, shook it up and the little metal picks supposedly cleaned the plug. Even though gasoline in those days was much less volatile than today, this sure sounds like something with dubious safety concerns.

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  • 2 years later...

Terry Bond

Member

Quote from Terry;

Reged: 05/02/00

Posts: 750

Loc: Chesapeake VA Re: Modern Champion Spark Plugs - bad experience? [Re: De Soto Frank]

#295520 - 05/09/05 10:20 AM

Spark plug history lesson #4-the earlier plugs worked better because they had a different insulator design-the center electrode was up in a recessed area inside the insulator. If the plug became fouled or sooted, the short circuited spark had further to travel to ground, so it took far more oil and soot to short them out. Remember the spark will jump only across the shortest distance. Realizing that, many early spark plug designs were based on what was known as the "Canfield Patent (1898). Modern spark plugs probably don?t have that feature. Center electrode is usually enclosed at the tip of the insulator giving spark shorter distance to travel. Our earlier cars probably run pretty rich to start with that that'll soot them up quickly, shorting them out faster than the earlier type with the center electrode up inside a deep recess area.

Terry

Dantewada, India

The very earliest plugs were made using French clay as the ceramic. Mica was also a popular insulating material (thin mica washers layered together). In the early days, the glazing was necessary to protect the porous and brittle ceramic. In 1916, Champion began using a mineral called <span style="text-decoration: underline">Siliminite</span> . They acquired the sole rights to mine this material when they purchased a competitor plug maker (Jeffrey DeWitt). Siliminite is so hard that a broken piece of it will cut glass. It?s been the material of choice for many years and glazing over it is not really necessary. I am not sure what other plug makers use for their insulating material but any post war major brand plug should be able to withstand blasting to clean the junk. Fine sand and low pressure of course! My personal preference however is to use the carb cleaner. I just feel better using it as I?m always worried about something getting stuck way up inside the plug, then letting go into the engine later. I?ve also seen folks just hold the business end of a plug up against a wire wheel and the result is a discolored ceramic, but no other significant damage.

As for a blasted insulator facilitating the "regrowth" of the gunk accumulation, I hope our mechanics are smart enough to know that clean spark plugs are not a permanent cure for bad rings, etc.

Terry

Existence of a heavy deposit of Siliminite/Kaynite has been unearthed by the Mining Department, at Kerapal & Koyavekur of Tehasil Konta India.

The following is copied from the Shop manual of the SUNBEAM-COATALEN V-8 OF OCTOBER 1916. Altho this engine has been referred to as the Worlds Worst V-8 engine the following is of some interest.

We recommend the K.L.G sparking plugs on these engines as being the only ones which have proven suitable for this purpose. The outstanding characteristics of these plugs is the central electrode, of which the point is nickel, which is made of copper and carries at the top a small copper radiator, combined with the heavy cross section of the conductor, ensures that the conductor is cooled. (Figure XL).

It will be appreciated that in engines of such efficiency as the Sunbeam-Coatalen Aviation series the internal heat generated presents designers a more difficult problem than any other. It is for this reason that porcelain sparking plugs prove quite unsuitable. The K.L.G. is a mica insulated plug. In point of fact, the only other insulation that will stand up to the work is quartz. At the present moment, however this latter is very hard to get. The K.L.G. firm has made the necessary arrangements to ensure that a continuous supply of their plugs shall be available for all Sunbeam-Coatalen aircraft engines. The KLG sparking plug is put together by means of hydraulic pressure. It is next to impossible to clean it by ordinary mechanical means. The method we employ, and which we advise others to adopt as being the most suitable, is to dip these plugs in strong soda and water, boiling them for a quarter of an hour or so then dry them rapidly in a hot place. This will remove any of the oil, carbon or other foreign matter which has collected in the pocket of the plug.

It should be remembered that behind the contact points of this kind of plug is a small pocket, and that any difficulty with the sparking will very likely cause stale gas of sorts to burn behind the points and in the pocket, where there is generally an accumulation of dead air with all the characteristics of a weak mixture. (Figure XLI.) Owning to its poor quality this dead air or stale gas in the pocket of the plug will burn very slowly, and so ignite the incoming or fresh charge in the cylinder. Thus it happens sometimes that an engine exhibits all the characteristics of a weak mixture when, in fact, the only fault is in this misfiring of a plug.

These plugs were 18mm by ½? reach and naturally no heat range seems to have been offered or even considered, these two things were to be addressed in the 1920s. However one can tell by the tenor of the writings that they were on the track of heat ranges.

Keep in mind that this was written in 1914. Later K.L.G (Or Lodge) plugs were made with a Pink insulator body and did not use the mica insulator. Just why KLG (Or Lodge) people claim to be the inventor of the modern spark plug has escaped me, maybe someone else knows, I certainly don?t know.

M.L. Anderson

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Good to see this topic surface again - MIca insulation is one of many different types that was tried over the years at various times. It goes back much earlier than 1914 and was actually used up into the 30's. These types of plugs were built up using very thin mica washers or discs. They were tightly compressed around the center electrode the form the insulation. It did work well when the plugs were new. The big problem with mica was that it quickly became impregnated with soot, dirt, oil, etc. They tended to short out more easily as compression ratios increased over the years. I recall years ago helping a frined try to find some plugs to run in his Indian motorcycle. I had a box full of old used green top Splitdorf plugs, and they had mica insulation under that green porcelain cap. We went through a dozen before finding one that would fire well under compression. They looked clean, but just didnt work.

Terry

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To T. Bond;

It may very well be that dirt in between the layers was the real reason for boiling the sparkplugs of mica as that may have been the only way to get in between the layers of Mica with any safe cleaning liquid. I have a KLG Type 341 and the round ground electrode is only half way across the central electrode. All of this being buried down inside the I.D. It looks as tho it is one cold plug similar to an AC G6 except for the G6 being a side firing ground electrode. I have a sketch of a genuine KLG for the Sunbeam-Coatalen V-8 engine which looks very much like the plug I have which is described above.

Since you obviously have been studying sparkplugs for some time do you have any opinions on the sparkplug invention time and by whom? It may be silly but for me people claiming something without any real explanation as to just what part of an invention it is is in the category of libel and false claims without any recourse by the true inventors.

I became very interested in this when I started a study of the old Oakland V-8 of 1930-31 which used the G series of AC sparkplug for only the two year span and then changed to a K series 14mm plug for the Pontiac V-8 of 1932. Also a sparkplug chart I found showed the sparkplug heat range was changed from 18 heat ranges to only 8 heat ranges. About this I wrote to Donald McKinsey and his statement about this was to the effect that the G series of plugs had far too many overlapping heat ranges of which I had suspicions as my study indicated. There must have been a lot of changes at AC from about 1928 to about 1938 or so. This is in regards to heat ranges and plug types such as the electrode arrangement plus the 1937/42 10mm fiasco.

It seems to me that at AC there was a sudden wakeup by someone about the heat range of various sparkplugs around 1927/1930. What makes me wonder is, ?Did the same thing happen at other plug manufacturers around the same time or was AC late in the realization that it was so?. For example did Bosch realize this earlier or was it a general happening as tetraethyl-lead became more available and less expensive, this being developed in the early 1920?s. One must remember that Tetraethyl-lead is a poison. It isn?t colored red for no reason. One only has to read about Jimmy Doolittle?s experience to realize this.

Yours, M.L. Anderson

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  • 3 weeks later...

The 10mm Sparkplug Fiasco

This started at Packard in 1937 with Champion plugs and then Packard went to Delco AC in 1940 and stopped in 1942. It may have gone on to 1949 but my information is hazy after 1942. One must remember the effects of WW-II on any automobile production which would include sparkplugs.

Buick 1941 one year only.

Cadillac 1939 to 1942.

Chevrolet 1941 & 1942.

Oldsmobile & Pontiac do not seem to have been deceived into this mess.

M.L. Anderson

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After many days of almost continuous search I found this address again under a different name and location. It gives so many different plugs that it is impossible to describe except under its address. I even found the almost impossible to find Delco AC C86S sparkplug does seem to exist as it is used on Tractors and seems to be the best and only genuine AC substitute for the old DELCO AC G12, D12 and J12 plug of the early 1930?s. Now if it is only true???

http://www.aep.bigstep.com/Master_Table_of_Cross_Reference.xls

M.L. Anderson

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To show anyone the perils of jumping to a conclusion about sparkplug conversion charts. AC must have ceased manufacture of the C87S 18mm by .500" reach and on the Champion crossover chart it is listed as a replacement with a 14mm $43.55 sparkplug!

Champion

Industrial plug 610 REL88B $43.55

14mm, 5/8"-24 shielded extension with 1" well depth, 1/2 in reach, 13/16 in hex $43.55

M.L. Anderson <img src="http://forums.aaca.org/images/graemlins/shocked.gif" alt="" />

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You people can undoubtedly help with a couple of sparkplug questions. Was the 10mm a technical fiasco, and if so, why? I have some 10 mm Dynamic plugs, which came to me when I was trying to work out the best arrangement for my Series 4 Mercer. It was not a problem to fit plugs to one set of valve caps for the other side of the Bosch 2-spark Zr4. The real trouble was the 7/8 holes above the bores, which have over an inch of thread to the combustion chamber roof. I doubt the plugs that were built for thesehave been available for 7 or 8 decades; and Morriss Burrows advised me that he used Hesselmann engine plugs which have long exposed electrodes. When I was his guest for the Glidden in 1980 we had so many things to talk about that I forgot to ask him to show me one.

I forgot to ask Ralph Buckley when I was there, too.

What I did, and it is not a perfect solution, was to make 7/8 to 14mm adapters, and skim down the body of the very longest reach plugs of that size, which put the spark nearly where it should be, but the plugs are more obstinate than I like when it comes to changing them.

What I am inclined to do this time, is to start with the very longest reach BG platinum aircraft plugs, and make new 7/8 thread bodies incorporating the points from the original 18mm bodies. We used the short reach BG 417S plugs in Wright Whirlwind R975 radial engines in converted Lee tanks that were used in the timber business and to clear the farm. They only had 12thou gap (why?), and the lower cylinders used to foul. When I was a kid I was expert at changing these. We had crates of these, and obviously they were valued more highly by the war authorities than we who got them from war surplus. Some of them were sealed in tin sleeves in boxes stamped "reconditioned".

My favourite old spark plugs were wide-bodied brass Oleo Magneto plugs. You could completely dismantle these to clean them. They were hard to find even in the 1960's, and I was able to obtain half a dozen from the man who sold me the Roamer-Duesenberg. I lent these to Stuart Middlehurst to use in his Alfonso Hispano Suiza, and over the years I never got to recover them. Stuart, however, had loaned me 25 of the 30 pounds purchase price of the Roamer; so I never worried too much though I wish I had some now for the 1911 Lancia.

Mention is made of the toxicity of tetraethyl lead, and while this is true, the problem in car exhausts may have been politically exaggerated. My understanding is that ethyl bromide, which likely had some anti-knock property, was present also in the fuel. And lead bromide is "fiercely

biologically inactive", to quote one of CSIRO's top chief research scientists who I worked ffffffor in the biotechnology area. We might judge that the choice of lead, which was equally effective as an anti-knock agent when fed as a fine metallic powder into the intake air according to Rickardo, may have been a sensible and relatively safe choice. Thallium was equally effective, as was tellurium according to a 1931 Popular Mechanics Ethyl ad I have beside me. Selenium was almost as good, tin less so, and arsenic way down the scale. Then the aromatic fractions of gasoline, which are best for knock resistance, have nasty carcinogenic effects. The only really good anti-knock agent that is not dangerous (unless you drown in it) is water!

What is the toxicity of platinum if we inhale or ingest it? (So many heavy metals are bad). The cousin of one of my friends operates air analysis equipment at Heathrow Airport, and plkatinum is consistently recorded! Where does it come from? Is it from degradation of catalytic converters? It is not an enzyme cofactor that is recognised, so it can hardly be beneficial.

Sorry I have followed this little trail away from the main topic; but it may provoke useful and informative comment from some more knowledgeble than I.

Ivan Saxton

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I suppose we have to guess that designers intended the spark olugs to occupy all but the last turn of the thread length in the engine. The L-head Mercer has 1.050" depth of thread from the top face to the chamber roof. As you realise, these are non-detacheable head engines, with threaded valve caps for servicing valves. I know there were some engine differences between 1915 and 1922: my engines are 1918 and 1919. I also checked the plug thread length in the 1923 Mercer 6, which has a detacheable head OHV Rochester Trego engine. I had forgotten about this, but the thread length for the plugs is 0.950". These are good measurements, and not guesswork. The six has provision for two sets of pugs on opposite sides of the block.

I have strong philosophic objection to machining the top face to run shorter plugs. I wish I had thought to ask Ralph Buckley while he was still around, but I saw both his 1922 Raceabout and the car 1915 Joe Fisher had on the 1980 Glidden, for which Ralph had just restored the engine, and neither had plugs recessed into the top of the block. I dismantled one of the long reach BG aircraft plugs this afternoon, and I am sure I can do what I said quite easily, particularly if I can obtain the correct 1/2"UN special fine thread tap. Incidentally, these 18mm aircraft plugs provide you with an excellent, easy, 18mm to 14mm splug adapter, because you can rethread the half inch hole in the body directly with a 14mm plug thread tap.

Another general question for you: When were the first commercial spark plugs made for cars with HT trembler or magneto ignition? David Dryden's 1904 2cyl Ford has 1/2" pipe thread, which seems to be the earliest standard. Somewhere I have not been able to find for a while I have an early 1920's local motor magazine which described what was said to be the earliest Ford in Australia, which was still in use by an elderly rural medico at that time. Interesting thing was that he had to make his own spark plugs for it, so it must have dated from a time before there were standards. This would have to date it before Ford became involved with corporate interests. How one of his early development cars may have got to this country is anyone's guess.

Ivan Saxton

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Ivan;

The 10mm fiasco was mentioned in the book, ?THE BUICK, A COMPLETE HISTORY? by Automobile Quarterly. Pages 226-227 explain it more thoroughly than I am able, but it seems that the plugs fouled at low city driving speeds. The insulator was too big on the outside diameter and not enough gap between it and the inside diameter of the outer body which did not allow the hot gases to scour and clean the insulator body. If that was not what it was then I haven?t any idea what it was as I haven?t an old AC104 to compare to a modern 10mm plug. New 10mm?s do not have the glass/glazing coating on the insulator to help the sparkplug from fouling since about 1976 as it is not needed with computer controlled fuel injection.

Packard Champion Y4 1937 10mm by .250? (1/4?) reach thru 1940 and certain models used AC 1042. Y4 was later replaced by UY6. AC 1042(?) from 1941 thru 1942

Buick 1940 thru 1941 AC104

Chevrolet 1941thru 1942 AC 104

Cadillac 1938 thru 1942 AC 104

Oldsmobile & Pontiac no 10mm sparkplugs used.

All of the cars using 10mm plugs later changed back over to 14mm plugs as most of them were using before the 10mm fiasco.

One must keep in mind that there were huge sparkplug changes from the late 1920s to about 1942 as they finally realized that making a lot of difference heat ranges sold a lot of sparkplugs even tho that many heat ranges were not needed, money talks we know. This was made abundantly clear when I studied the AC sparkplug chart that compares the ?G? 18mm series of sparkplug to the next ?K? 14mm series of sparkplugs. They dropped the number of heat ranges from 18 down to 8. The ?K? series seems to weigh only about two thirds as much with cost factors reduced somewhat too a like amount. I just wonder how many more could be dropped in view of the amount of sparkplugs that are dropped for various reasons. One must remember that there are three reasons for doing something. #1.The right reason. #2. The wrong reason. #3. The real reason, usually money.

M.L. Anderson

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