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Letters and Miscellanies

Notes and Responses From Readers

| March/April 2002

  • Bulls eye

  • Bulls eye

Get the Right Plug

After reading the Stationary Engine List by Helen French in the December 2001 issue of Gas Engine Magazine, I find there needs to be a lot of enlightenment about spark plugs. I have been advertising and selling obsolete and vintage spark plugs for somewhere around 15-20 years in GEM. I have been supplying spark plugs to restorers and collectors in all phases of the hobby for 20 years and have an extensive library and computer files dedicated to this purpose.

I am also the reference for Champion Spark Plug Co., Autolite and AC Flint customer service referrals for obsolete spark plugs, and I talk to their service personnel on a fairly regular basis. I enclose a page of spark plug information when I send out inquiries, and 1 think the information in it could be of benefit to GEM readers.

First, let's define the problem with the new spark plugs. When automobiles became computer controlled, the spark plug did not have to have the bottom of the insulator glazed. New cars have fuel injection, and the computer will not put enough gasoline into the cylinder to flood it. It injects fuel into the cylinder and says, 'I will not put any more fuel into the engine until it fires.' Then, it fires the cylinder with 40,000 volts. If something happens to this computer control and too much fuel is injected into the cylinder, and the engine floods, this vehicle will not run right until you have replaced the old plugs.

What has happened is the trash gasoline that has been forced on us contaminates the spark plugs because they are not glazed on the bottom. However, when was the last time you flooded a computer-controlled vehicle? More than likely, never.

Now, these old engines do not have a computer control, and if your carburetor is running rich or you flood the engine, the same thing happens. The bottom of the insulator where it fires the engine becomes contaminated and becomes junk. The point coil or magneto ignition does not have 40,000 volts to fire the spark plug.

The solution to this problem is to find the spark plugs that were manufactured prior to the time that they quit glazing the bottom of the insulator. In those engines that used 1/2-inch pipe thread spark plugs or 7/8-inch by 18 thread plugs, the best deal is to try to buy spark plugs that come apart so the insulator can be taken out and cleaned with WD-40, kerosene, diesel fuel, or other things that will remove the glaze on the bottom of the insulator. In any case, do not sandblast or glass bead them. This removes the glaze and you have a short plug life just as though you had purchased one of the newly manufactured spark plugs.


Gas Engine Magazine A_M 16Gas Engine Magazine is your best source for tractor and stationary gas engine information.  Subscribe and connect with more than 23,000 other gas engine collectors and build your knowledge, share your passion and search for parts, in the publication written by and for gas engine enthusiasts! Gas Engine Magazine brings you: restoration stories, company histories, and technical advice. Plus our Flywheel Forum column helps answer your engine inquiries!

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