Re: lead additive for old engines ??

Posted by Clooney on August 13, 2004 at 10:49:55 from (198.208.159.14):

In Reply to: lead additive for old engines ?? posted by Joe P. on August 13, 2004 at 10:04:48:

Joe, there are very few outlets of "TETRAETHYL LEAD" as it is banned in most areas.. Most of the lead additives are a “Lead Substitute” & those don’t do much for octane rating but do somewhat help valve seat recession..

You ask—
Quote: “Wasn"t the idea of the lead to soften the impact on the valves and seats?”…. Answ,,That was one of it’s assets.. It actually didn’t soften the impact as much as keep the valves from sticking to the seats as they cooled when they settled in their seats.. The other added benefit was, it did boost the octane rating of the fuel.

Quote: “The sellers also claim the addition of this lead increases the octane level of the gas. If true wouldn"t this be a good thing?”….Answ,,Not necessarily so.. Using a higher octane than your engine requires to operate without preignition & detonation gains you nothing & can even lower engine performance slightly.. Most people see higher octane as more power.. Actually octane [rating] is the ability of gasoline to not ignite under heat & pressure… Higher octane CAN add power if the engine compression ratio & spark timing is also raised to take advantage of the harder to ignite fuel.. Adding octane [rating] to fuel where it isn’t required do to the engine having higher compression or better combustion can lower the MPG slightly & impede starting slightly..

My personal feeling on using lead or lead additives in old cars, trucks, & tractors is: unless the engine is run hard, & hot enough, & long enough to turn the muffler red [red hot] the lead additive isn’t needed & can cause other side effects like spark plug fouling & valve cokeing… Even on hard run engines [boat & aircraft engines especially] the use of a low amount of lead will help prevent valve recession due to the valves distorting the seat as the red hot valve shrinks as it cools in the seat & pulls the seat metal with it..

Early on when low lead & no lead fuel was first sold the auto companies did extensive testing & what was found was for most operating conditions the lead wasn’t needed.. On industrial engines, heavy duty trucks [the few left with gas engines] & continuous high RPM hard working engines the lead was still needed due to valve seat wear.. On the tractor situation: most old tractors are used for light duty anymore so don’t need the additives.. For hard continuous field work it probably wouldn’t be a bad idea or at least watch the valve clearance & if the valve lash starts to close up add some lead or install hardened valve seats & stellite valves..

If the old engines would function without lead under all loads & conditions why are almost all the newer engines [ built since no lead appeared] have hardened valve seats & tougher valves?

JDClooney@aol.com

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