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Farmall Tractors Discussion Board |
Re: Engine Problems from Unleaded Gas?
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Posted by Phil Auten on September 18, 1999 at 21:08:27 from (206.175.72.226):
In Reply to: Engine Problems from Unleaded Gas? posted by Fred on September 18, 1999 at 17:36:24:
Fred,
The lead on the older gas helped do two things. First, it raised the octane rating to prevent preignition or "pinging". Second, it lubricated the valve seats and their mating surfaces on the valve head to prevent the problem that Johnny described below. It also lubricated the valve stems and guides. Of course all this was done to make the gas more friendly to the high compression engines in the cars of the day. Those cars were running compression ratios of 8:1 up to 12:1. These old tractors run compression ratios from 4:1 up to about 6:1 for one with high altitude pistons and a milled head. Basically half of what the cars used to run. Combustion temperatures are also much reduced and tractor engines do not turn over 2000 RPM or so. I haven't experienced any problems with unleaded gas yet and don't expect to in my lifetime as I don't work any of my old tractors hard. If you are going to hang a 4 bottom 16" plow on your Super M and pull it all day in heavy clay soil, I would be inclined to add a lead substitute, just as a preventive measure. Like the little Jewish Grandmother's chicken soup, "It couldn't hurt".
I have gone to hotter plugs because of the fouling problem, but like I said, I don't work the tractors very hard and that tends to aggravate the fouling. Champion D-21's seem to work well in the M that I use for mowing pastures and bar ditches.
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