Lead additive

1950 - 1952, M38, questions, discussions, regarding anything related to the M38.
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Scott in NM
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Lead additive

Post by Scott in NM » Mon Jul 16, 2018 7:57 pm

Probably has been a previous discussion but couldn't find it so I'll ask the question here.

After several decades of self-repair, my M38 had a lack of power I couldn't find the cause but I did attribute it to the time I replaced my oil pump and FUBAR'ed from there. Took it to mechanics that restore old cars, well recommended, and quite pleased with the result. However, they said NOT to put in lead additive as it just junks things up, the engine did not need it. I have a chemistry degree and understand mechanics, so I can follow the logic of an opinion, but do not know if this is accurate. What does the board say, lead or no lead in the gas?

Also, is there a procedure written that I can study to time the engine using vacuum, i.e. what and where to hook up equipment and how to use it, etc?

Scott

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Re: Lead additive

Post by Radtech » Tue Jul 17, 2018 1:02 pm

The problem today is not the lead but the ethanol added to gas today.Ethenol can be very bad on old engines.

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Re: Lead additive

Post by dpcd67 » Tue Jul 17, 2018 2:14 pm

Do a search here and you will find lots of info on using vacuum gauges. Most of them have the instructions printed with them. All I use for timing is a vacuum gauge and my ears. Never owned a timing light and don't need one.
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Re: Lead additive

Post by Gummy1950 » Sat Jul 21, 2018 5:08 pm

The M38 was designed to run on very low octane gasoline. Lead would be useful if you don't have hardened valve seats, but that's about all. Ethanol is much worse - not for the motor, but things like fuel pumps and carbs. I have been running plain old regular gas for thirteen years now and no ill effects - except for the carb gasket was turned into mush. Otherwise, all OK.

But - use stabilizer unless you're going to burn it up quickly to avoid phase separation.

My .02.

Mark Jesic
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Re: Lead additive

Post by Mark Jesic » Sun Jul 22, 2018 5:55 am

I use an addative in mine, as recommended, seems to run slightly smoother, although it was O.K. before. I guess i was after peace of mind. :D


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Re: Lead additive

Post by Wolfman » Wed Jul 25, 2018 7:03 am

Gummy hit on the purpose of leaded gas. The valve seats. Or lack of.
Old engines, like an L-134 did not originally have valve seat inserts. The seats were cut in the block itself and were soft, compared to the hardened seats used today.
That is why there was lead in the gas. Tetra-ethyl lead ?? Am I close ?? It cushioned the seat so it did not " Hammer" out. In these engines, no lead and the seats failed pretty quickly, especially under heavy use., and you had to adjust the valves constantly.
Lead also has other bad side effects. Beside being poisonous, it would survive the combustion process and be blow out the exhaust. Was polluting our world. Also because it would survive the combustion process, it left what looked like carbon deposits on valve stems. Valve heads and inside the combustion chamber. When scraped or buffed off, it came off as a white powder. "BAD" in a concentrated form.
If you have hard seats installed, you don't need lead, or " lead additive". As I have said before, anything that gets past the combustion process is going to be banned by the EPA, so, the additive might help the intake valves but won't make it to the exhaust valves. ( If it does, it is probably illegal to use ! )
Ethanol. :twisted: That is another topic !
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Re: Lead additive

Post by YLG80 » Wed Jul 25, 2018 10:12 am

In 1975, the US army has made extensive tests on many unmodified vehicles with unleaded fuel.
The conclusion was clear: they could not link any engine problem to unleaded gas even exhaust valves recessions.
The study is available on the Net.

However since that study, it's admitted that if your vintage engine is operated continuously above 3500 rpm or in heavy load conditions, then you will have problems.
For that reason I will never drive my jeep on a highway :D
In the past, I've seen columns of jeeps going to the Normandy beaches via the highway, with a minimum speed of 70km/h
I'm located in Belgium and Normandy is not close to Belgium :D :lol:
I'm pretty sure it was a disaster for the engines.
Other than that I simply add some lead substitute additive to the gas.
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Re: Lead additive

Post by DogDoc » Wed Jul 25, 2018 10:33 am

On the subject of additives, what about isopropyl alcohol added to the ethanol free gas periodically to "clean" the carburetor?

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Re: Lead additive

Post by Gummy1950 » Wed Jul 25, 2018 10:54 am

I would prefer to change my fuel filter. Gas has enough alcohol in it already. If you drive THAT many miles, maybe take the carburetor off and clean it on the bench. I know several convoy participants. I'll ask them about 5,000 miles + per year and gasoline/lead/ethanol.

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Re: Lead additive

Post by YLG80 » Wed Jul 25, 2018 11:18 am

DogDoc wrote:
Wed Jul 25, 2018 10:33 am
On the subject of additives, what about isopropyl alcohol added to the ethanol free gas periodically to "clean" the carburetor?

Jay
Jay was talking about ethanol free gas.
Yes the alcohol is good solvent for gums accumulated in the carb.
The cleaning additives have a good percentage of alcohol in their composition.
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Re: Lead additive

Post by Scoutpilot » Wed Jul 25, 2018 12:58 pm

Also, is there a procedure written that I can study to time the engine using vacuum, i.e. what and where to hook up equipment and how to use it, etc?
Look here. http://oldjeepcarbs.com/thread/29/time- ... ming-lightThere is a video there as well.
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