Lead fuel

General help and support for your Lindeman through 2010 John Deere crawler
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ironyetty
430 crawler
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Lead fuel

Post by ironyetty » Sun Apr 15, 2007 12:02 pm

Since older motors where set up to burn leaded fuel does the newer gas have any adverse effects on the motors? Should I be adding a lead additive to try and substiute this absence of lead?

Just curious.

Thanks
Ironyetty

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Lavoy
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Post by Lavoy » Mon Apr 16, 2007 7:51 am

If you put on a ton of hours, you might have increase valve wear. I put hard seats in all of the heads I have done for this reason. I really do not believe it is an issue unless you are running the machine 8 hours a day every day of the week.
Lavoy

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hunter41mag
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Post by hunter41mag » Tue Apr 17, 2007 5:50 am

I agree with Lavoy that the problems with older engines running unleaded fuel increase valve/seat and guide wear. But if heads are rebuilt with the latest parts that are hardened than this should not be an issue.
Don
Eastern PA
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Stan Disbrow
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Post by Stan Disbrow » Tue Apr 17, 2007 9:30 am

Hi,

No, not a problem at all. I don't know of any old tractor engine design that cared if the gas had lead in it or not.

Most of the gas sold until 1960 or so was unleaded, anyway. The addition of Tetraethyl Lead was something that occured in aviation fuel first, and then not until WWII as a standard thing.

The reason for adding TE to gas is to allow the use of lower grade gas in high (10:1 and up) compression engines. This became important in WWII as ever greater power was required from aircraft engines at the same time ever faster methods of fuel production were necessary.

Before that, the few high compression engines used specially produced and graded fuels without the addition of TE.

The whole purpose of TE is to prevent detonation, which will occur with high compression. It wasn't until the late 1950's with the Horsepower Wars in cars that made TE common in all the pump fuels.

Obviously a JD 420 style tractor engine isn't High Compression or involved in Horsepower Wars, so TE wasn't ever necessary.

When it comes to valves, there was a problem to think about when the fuels were switched to Unleaded in the late 1970's. TE tends to leave deposits on the valve seats and faces. These deposits are always flaking off, but get 'replated', if you will, by new TE liberated from the fuel during combustion.

If you suddenly lost the TE, then the flaking would lead to gaps along the valve faces and seats and let fire leak past. This could easily lead to valve damage (burnt valves). This would be a greater problem for engines with higher compression than for those with lower compression.

At the time, many people 'weaned' their engines off of TE by altering the mix of Leaded and Unleaded each time they filled the tank (9 gals to 1 gal, then 8 gals to 2 gals, etc, until they were using only Unleaded).

These days, you haven't that luxury (unless you want to go to the airport and buy Leaded Av Gas at $10 a gallon), so just stick Unleaded in there ad go.

Oh, and use the Low Grade (87) not the Mid or Premium grades of pump gas. There's less Alcohol and MBTE in Low Grade and the old carburated engines will start easier as a result. ;)

Stan
There's No Such Thing As A Cheap Crawler!

Useta Have: '58 JD 420c 5-roller w/62 inside blade
Useta Have: '78 JD350C w/6310 outside blade
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