Lead used to lube valve stems?

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Truckedup
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Lead used to lube valve stems?

Post by Truckedup »

It's repeated on bike forums that years ago the tetraethyl would lubricate the valve stems , reducing wear.....is there any truth to this? I see the intake valves running hot enough to instantly evaporate and fuel hitting them, what happens to the lead,I don't know....
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Re: Lead used to lube valve stems?

Post by pdq67 »

Yes!

I have junked many an old stove bolt 6-banger and found light gray lead paste in the top of the heads and in the oil pan sump corners.

You know, "money speaks and BS walks"!!

Back when they were R & R'ing Tetra Ethyl Lead, they knew how poisonous it was because a couple of Lab. Techs died because of it!

BUT it was and still is such good CHEAP octane improver that they said to hell with and sold it anyway!!

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Re: Lead used to lube valve stems?

Post by Truckedup »

I use leaded VP C12 in my race bikes...I like look of the light gray lead deposits on the bike frame from the exhaust just like pump gas years ago..
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Re: Lead used to lube valve stems?

Post by naukkis79 »

Main protection from lead is for exhaust valve/valve seat contact. Lead plating in those surfaces prevented material welding together and so reduced wear greatly.

But lead stuck everywhere, sticking into hot valve stems was harmful side-effect not desired. Lead also stuck to other parts of valve face like super sticky deposit and was really pity to remove.
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Re: Lead used to lube valve stems?

Post by PackardV8 »

Te lead did work to lubricate valve stems. Today's head rebuilds of older engines require additional stem-to-guide clearance to avoid hanging a valve on startup. The old guys had to learn new tricks when unleaded and now ethanol became the standard.
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Re: Lead used to lube valve stems?

Post by naukkis79 »

PackardV8 wrote: Tue Aug 04, 2020 2:19 pm Te lead did work to lubricate valve stems. Today's head rebuilds of older engines require additional stem-to-guide clearance to avoid hanging a valve on startup. The old guys had to learn new tricks when unleaded and now ethanol became the standard.
Lead increases heat transfer between seat and valve greatly, I think that hanging valve is just about clearances not lubricating effect. Usually lead deposits in valve stem makes them bit sticky to guides - with unleaded fuels valve removing won't need force at all - with leaded fuels some force is usually needed.
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Re: Lead used to lube valve stems?

Post by PackardV8 »

naukkis79 wrote: Tue Aug 04, 2020 2:45 pm
PackardV8 wrote: Tue Aug 04, 2020 2:19 pm Te lead did work to lubricate valve stems. Today's head rebuilds of older engines require additional stem-to-guide clearance to avoid hanging a valve on startup. The old guys had to learn new tricks when unleaded and now ethanol became the standard.
Lead increases heat transfer between seat and valve greatly, I think that hanging valve is just about clearances not lubricating effect. Usually lead deposits in valve stem makes them bit sticky to guides - with unleaded fuels valve removing won't need force at all - with leaded fuels some force is usually needed.
We'll have to agree to somewhat disagree on this one. All I know is all us old guys who were doing heads in the lead era learned the hard way it was necessary to open up the guides with unleaded.
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Re: Lead used to lube valve stems?

Post by Truckedup »

On the old bikes the valve to guide clearance was .0025 to .0035 because the valve seat runout tolerance could stick a valve with tighter clearances . Now with fancyass valve facing machines the guide clearances can be .001 to 0015 without a valve seizure...Pretty tight on air cooled engines running pump gas..
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Re: Lead used to lube valve stems?

Post by PackardV8 »

Truckedup wrote: Tue Aug 04, 2020 5:12 pm On the old bikes the valve to guide clearance was .0025 to .0035 because the valve seat runout tolerance could stick a valve with tighter clearances . Now with fancyass valve facing machines the guide clearances can be .001 to 0015 without a valve seizure...Pretty tight on air cooled engines running pump gas..
FWIW, there's old-stock-two-piece-plain-stem-valves and there's current production one-piece-chromed-stem valves. One has to know what goes with what. I just used up the last of my NOS-Eaton-Packard-script intake valves. Henceforth, we'll be using new production and even though it's furrin' produced, a much better valve.
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Re: Lead used to lube valve stems?

Post by Truckedup »

Jack, for the old Brit bikes, current guides are manganese bronze or a harder nickel-aluminum bronze. Valves are uncoated stainless steel or nitride coated stainless.
. Original valves I have seen were one piece stainless steel exhaust and a magnetic steel intake. Guides were a variety of bronze or cast iron. I don't know if any where were chromed, but there's a lot I don't know..
In the times of leaded fuel, guide life on a hard ridden Triumph was as short as 15,000 miles. With better modern guides, and considering most vintage riders aren't abusive, maybe 50,000 miles. I have the valve work done on a Newen single axis machine. I do know several shops using "hand held" tools that keep run out presise enough to run tight valve to stem clearance, many shops can't .
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Re: Lead used to lube valve stems?

Post by David Redszus »

Lead, in the form of TetraEthylLead, TEL, or TetraMethylLead, TML, have been used as fuel additives for
over 70 years until finally banned in the West, but is still used in some parts of the world.

TEL is a lead atom connected to four ethyl radicals. Exposed to the heat of combustion, it will
decompose to form lead oxides which are useful to control detonation.

However, lead oxide causes a number of issues. The oxide acts as a contaminant at the valve to
valve seat interface to prevent microwelding and resultant valve recession. It is not a lubricant
but rather a cushioning film.

But the deposit levels increase with use. Bromine compounds are added to act as scavengers
to reduce deposit build-up.

While TEL, in its liquid form is quite deadly; as an emission product, lead oxide is harmless
except when ingested (don't eat paint chips you stupid kids), and when ingested by catalytic
converters and oxygen sensors. Lead oxide coats the ceramic substrate and renders them useless.

It does not help valve stems one bit. With hardened valve seats, it is not needed for valves.
With improved, high octane fuels, it is not needed to control detonation except in the
most extreme cases.
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Re: Lead used to lube valve stems?

Post by BCjohnny »

Been meaning to reply to this but been too busy to find the citation ..... I'll try and look it up

Very high levels of TEL or such, in aero use knock suppression, actually causes exhaust valve and seat problems

So too much can be a bad thing ........
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Re: Lead used to lube valve stems?

Post by Kevin Johnson »

https://ntrs.nasa.gov/api/citations/199 ... 093400.pdf

THE EFFECTS OF AN INCREASE IN THE CONCENTRATION OF ETHYLENE
DIBROMIDE IN A LEADED FUEL ON LEAD DEPOSITION, CORROSION
OF EXHAUST VALVES, AND KNOCK-LIMITED POWER
By B. A. Mulcahy and M. A. Zipkin
Driving Force Online: BREAKING NEWS—Ohio Governor Signs SEMA-Supported Vehicle Freedom Bill Into Law!
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Re: Lead used to lube valve stems?

Post by hoodeng »

Dave is on the money with the application of TEL.

Guide clearances over the years have not necessarily followed fuel composition, i will quote inlet valves only in the following.

Harley Shovel engines started out with .002"-.004" without seals up till 1980 in 81 they went down to .0009" to .0026" and used stem seals. In the Evo engine they went down to .0008" to.0026" and used stem seals. In 99 with the introduction of the Twin Cam, and through to the current M8 they have not changed from .001" to .003" these later engines can run hot as hell and not have a problem.
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Re: Lead used to lube valve stems?

Post by Circlotron »

Truckedup wrote: Tue Aug 04, 2020 8:58 am I use leaded VP C12 in my race bikes...I like look of the light gray lead deposits on the bike frame from the exhaust just like pump gas years ago..
Yeah, the light grey coating looked cool. Back in the day, folk wisdom said that when you took your car for a good run on the highway the pipe turns grey because the engine is running “better”. Eventually I realised the pipe colour was actually a consequence of its temperature. At highway speeds for extended periods the pipe will certainly get hotter. Two things proved this. 1/ if you removed the pipe and cut it into sections it would get lighter and lighter colour the closer you got to the engine, even if it was quite dark at the tailpipe. 2/ back in 90 or 91 I was messing with my latest home made crank trigger and advance curve box and on the way to work for the last half mile I switched it to fire only at the initial advance setting, 6 deg BTDC and floored it. Heaps of white smoke out the exhaust and the inline six manifold almost melted off. Checked the colour of the pipe when I got there and went and got a sheet of white paper to compare and and the pipe was every bit as white as the paper. All that in maybe 40 seconds of full throttle. :twisted:
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