Re: Engine Problems from Unleaded Gas?

Posted by Johnny Angel on September 18, 1999 at 19:11:58 from (209.240.197.14):

In Reply to: Engine Problems from Unleaded Gas? posted by Fred on September 18, 1999 at 17:36:24:

We had a fuel dilemma a few years ago with aircraft gasoline. Planes like my '46 Stinson used 80 octane leaded Avgas, which was phased out. The alternative fuel that became the airport standard is 100 octane LL (Low Lead). This is what we discovered:

Lead lubricates the valves where they seal against the seats. Without the lead, the valves would stick to the seat, then as the pushrod forced them open, they would pull a little piece of metal out of the seat. 2 million cycles or so, and the seats were so pitted, they had to be replaced.

The replacement seats (as with modern automobile engines) are much harder and will take more abuse than seats made in the 40's and 60's.

I run a lead substitute in my Super H. Once a friend brought me a 5 gallon can of gas to the field where I was disking and ran out. It was straight unleaded. Since the old Farmall was pulling hard against the disk and the governors were open and the power near max, I was getting concerned for the fate of my valves. Though no ill effects seem to have occurred, I am still uncomforatable with using unleaded gasoline without an additive to protect the old engine. Just my humble opinion. :)
Johnny Angel CessnaPilot@webtv.net

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