Re: Re: Re: Re: Re: Re: Old engines (pre 1970) and gasoline, leaded - unleaded

Posted by Bill Jones on January 04, 2002 at 10:43:27 from (63.17.133.238):

In Reply to: Re: Re: Re: Re: Re: Old engines (pre 1970) and gasoline, leaded - unleaded posted by Salmoneye on January 04, 2002 at 04:50:19:

In doing some research,I found that the "microwelding" you referred to is known to me as "valve wear".Matter of fact it is caused by using cast iron seats,a thing of the past.In my field of aviation,the FAA Technical center found that the engine valve seat recession(wear) was not "significatly different" when using either leaded or unleaded fuels.As far as the lead burning holes in valve seats and exhaust pipes,look in the Kettering link you gave ,under"The trouble with tetraethyl lead" chapter,paragraph 4.I looked through my own papers and found the burn-through info.Then I happened to go to the link YOU provided,and actually read it,and look what it says.Did you read your own link?Perhaps you should read my post a few weeks ago on the farmall board on the history of TEL.Also,Preignition and Detonation are related ,but NOT the same.Preignition is caused by local hot spots inside the cylinder.These can be incandescent particles of carbon or red hot edges of a valve.If the mixture is ignited and begins to burn while the piston is moving upward too early on the compression stroke,the air inside the cylinder heats and begins to expand,opposing the movement of the piston and decreasing the engines power.The long burning period of the fuel-air mixture releases more heat into the engine than it can dissipate,and the cylinder head temperature increases.The unburned fuel and air in the cylinder is heated and compressed to its critical temperature and pressure.This causes it to explode or Detonate.Detonation acts like a hammer blow at a high temperature and it can actually burn a hole in the piston head.Detonation can destroy an engine within a few seconds. I mentioned distillates only to point out that there was no TEL added to them,but distillate fuel manifolds were available on IH tractors until the letter series were discontinued.The "microwelding" only occurs at high temps (300C) and high RPM(greater than 4500 rpm),or at least that is what I found out,loading or lugging the engine has no effect.TEL does in fact "retard" in a way.It causes brain damage.You spelled Porsche incorrectly,do you own one?

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