Re: lead additives to use..or not.....and why
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Posted by Steamer on November 25, 1998 at 09:01:09:
In Reply to: lead additives to use..or not.....and why posted by greg from jackson mi on November 22, 1998 at 05:57:17:
: I have a mh 50, Iam now using a lead additive in my gas. I had a Min.- Moline-BF Avery.mod BF.
: I never used any lead in it. I devoloped a lot of oil burnning problems. I took the motor apart expecting to see a lot of piston wear. beleive it or not the pistons looked very good. (rings too) which leads me to beleive that oil got in through to valve stems.
: now I hear that putting lead additives is not allways the best for an engine. I sure would like other opinions. whats yours? The addition of Lead into gasolene occured during the horsepower wars in the automotive industry in the 1950's. The horsepower increases in the cars came from using higher compression in the engine. Gasolene will not burn well under high compression, but will explode instead. This is referred to as detonation. The Lead additive would raise the point of detonation of the fuel. It also would leave a coating of lead on the valve and seat faces. This would cushion the valve impact during the rapid burning of the fuel under the high compression (13 or 14 to 1 in those motors). Now, none of our tractors have compression high enough to warrant the use of Lead additives to prevent detonation. At least not stock machines :-) However there is a problem with suddenly switching from Lead fuel to unleaded fuel. The Lead additive leave that coating on the faces of the valves and seats. It tends to flake off over time, but the additive is constantly replenshing the coating and all is well. Once the additive is suddenly removed, the lead coating will likely flake off in one spot. This leads to a poor seal, allowing fire to blow past the valve seat. This will lead to a burned spot on the valve. This is the mechanism that damages and burns the valves in tractors. There is no detonation risk, since our compression ratios are so low (detonation causes other damage). One way to deal with the problem is to pull things apart and either clean or replace the valves and seats. The other way is to slowly reduce the amount of Lead additive in the fuel and allow the valves to clean themselves. When we were switching from Leaded to Unleaded gas I did this with a dozen engines, and it worked out well. They've been running unleaded gas for many, many years. Oh, keep in mind that most fuels were unleaded until around 1950, and many of us have machines older than that.
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