By Steve Thompson
Progressive Farmer Contributing Editor
QUESTION: Edwin Shrift, a fourth-generation farmer from Summerhill, Penn., has a question about his 1940s H Farmall he still uses around the farm. Edwin likes to drive the old tractor, even though the air conditioner only works well on a cold Pennsylvania morning.
His problem is one with older gas tractors: trying to adapt that tractor to today's gasoline blends. The tractor's plugs are fouling.
After checking everything -- even running a compression check and finding it normal with no oil on the plugs, completely rebuilding the distributor electrical system and installing about three carburetor kits -- the problem didn't go away.
When he told me that he has even added a considerable amount of octane boost using the highest octane fuel he could buy, he probably gave me the answer to his problem.
ANSWER: Older gas engines need to drink low-octane fuel. It is often thought that high-octane fuel burns faster than low octane, but it's really the opposite.
You want your old engine, designed to run on regular leaded gasoline, to have a radical burn. And the lower the octane, the more radical the burn, which can keep your plugs from fuel-fouling. Adding octane boost will only help foul the plugs more quickly.
If this doesn't fix the problem, Edwin should consider an electronic ignition system available at tractor-supply stores.
This steps up the voltage considerably and is a great asset to any old tractor trying to run on today's fuel.
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