Re: Recommended Gas

Posted by Bob Johnson on June 10, 1997 at 09:29:30

In Reply to: Recommended Gas
posted by Leo Stacks on June 10, 1997 at 07:21:32

Leo,
The short answer is use regular unleaded gas and you do not need an addative.
The long answer is.When the Model A was built leaded gas was not widely available.Lead was added to the gasoline after WWII to increase the octane rating for the higher compression engines. By the late 60's compression ratios were over 10 to 1 and octane ratings were over 100. It was found that the lead in the gas helped soften the pounding of the valves against the valve seats and auto manufacurers were able to use valves and seats that were fairly soft.The Model A engine has a compression ratio of only 4.22 to 1 and can get by with very low octane gas (regular has more than enough octane).In fact during WWII some people would run their Model A on kerosene, after starting it with gas.As for the valves.The Model A engine originally came with exhaust valves that were harder than the intake valves.There were many replacement valves offered in the past that were soft and could fail.However most of the valves these days are hard (stainless steel) and should not cause a problem.I have also heard that the problem with burnt valves is related to engine speed and does not start until the engine is turing at 3000 rpm, above the redline for a Model A.
Bob

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