Re: lead additives to use..or not.....and why

Posted by Nate on November 24, 1998 at 09:49:15:

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:

As for the valve guides, no lead on earth will do a damn thing. The fuel and it's byproducts just dont go there in enough quantity to do anything. As for the valve seats themselves.. when fuel with tetraethyl lead is burned it leaves deposits on the faces of the valves which cushion the impact of the valves when they contact the seats. The speed of contact and hence the force of impact is what can do damage. Working it hard or lightly makes no difference if the engine is going the same speed. As for needing to use it in a tractor engine it is unlikely it would make much of a difference. I had a chrysler 440 I ran with soft valve seats for about 60000 miles with minimal visible damage to the valve seats. Now that's probably 1500 hours, if you consider that the average engine speed was probably 2500rpm and just for argument's sake the tractor is 1500rpm that would decrease the valve speed by 3/5, so the valves would last 2500 hours. then if you consider the valve lift was .557" and the average tractor from the 50's is about .300" and valve speed is related to that by the square of the % change in lift... ((.557/.300)/.557)^2= .212 then we can further increase the hours by 2500/.212 = 11800 hours. This is probably how many hours you'd have to put on before you really wore the valve seats any appreciable amount. At that rate I'd just run it and replace the seats if they ever wear out. It certainly would cost less than 11000 hours worth of lead additive. As for oils, diesel oil, marvel mystery oil, they do nothing for the valve seats no matter how many people tell you they do.

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