[Healeys] Hardened seats in a cast iron 100 head

[Bob Spidell]

Full story: https://en.wikipedia.org/wiki/Thomas_Midgley_Jr. and 
https://en.wikipedia.org/wiki/Tetraethyllead

In a book on aircraft maintenance I have buried in a box somewhere there 
was more: Midgely, at Sloan-Kettering--inventors of the electric starter 
BTW--tested over 4,000 compounds and found tetraethyl lead (TEL) to be 
most effective at preventing detonation, allowing higher octane fuel 
hence more powerful, higher-compression engines (and, presumably, it was 
suitably cheap--this is the first I've heard of this conspiracy theory, 
though it's plausible). Allegedly a serendipitous side effect, TEL 
causes thin elemental lead deposits to build on exhaust valve seats 
which offered protection--a sort of cushion--from erosion of the seat 
onto the valve backside of the valve (and does somewhat cool the valve). 
I have never come across anything that attributes the need for TEL to 
'poorly designed' ignition systems (I'm open to evidence). ICE aircraft 
engines have used magnetos almost from Day 1--SS systems have been tried 
but generally found lacking--and most engines have two (they'll run on 
one, but produce more power and run smoother on both). A properly tuned 
magneto will throw a massive spark and they are quite (necessarily) 
reliable (dirt track cars, for one, still use them, requiring push 
starts). They're usually timed at 20-25deg BTDC and have no provision 
for advance/retard. Modern small engines, from chainsaws and lawnmowers 
to quads, use a form of magneto, driven and timed off the crankshaft. I 
sometimes tell people piston aircraft engines are glorified lawnmower 
engines.

Gasoline for ICE aircraft--'avgas'--still contains a significant amount 
of TEL; enough that, in some lower-compression engines elemental lead 
can form on spark plug electrodes causing misfiring, which can be burned 
off with a short ground run at high RPM at max lean condition. There is 
considerable research ongoing to create a suitable replacement for TEL 
in ICE aircraft engines and, IIRC, there is a mandate from the FAA to 
remove it (someday). The major engine manufacturers, Continental and 
Lycoming, are quite resistant as they get enough lawsuits already. Since 
ICE aircraft cylinder heads are aluminium they have always required 
inserts.

As for conspiracies, Henry Ford initially wanted to use ethanol--he 
could refine his own, like he tried to make his own rubber in S. 
America--as fuel for his cars, but someone--I believe it was 
Rockefeller--'convinced' him to use gasoline which, at the time, was a 
nuisance byproduct of the refining process of kerosene for lamps. See 
also: How Ford and Firestone conspired to 'kill' public transportation 
in US cities.




On 8/25/2024 10:23 AM, Hank Leach via Healeys wrote:
> I do not recommend that you do hardened seats. Chance of damage to the 
> head is high and then you will be stuck with Aluminum.
> There is no need to change the seats just because we lost lead in fuel 
> or that octane is reduced. If you drove the car daily and put on mega 
> miles a year this might be a consideration but with today's conditions 
> that probably is not going to happen. The seats will last forever.
> Lead to reduce knock was only needed in the early 1900's when ignition 
> equipment was poorly designed. The entire lead fiasco was a ruse by 
> the Ethyl industry to sell fuel...it was never needed and finally 
> banned in all but 6 countries.
> The "additional" advantage of cooling the valves was not much of a 
> benefit and lead substitutes today are just alcohol and not really 
> effective.  Exhaust valves run at 1800 degrees despite lead or lead 
> substitutes. Don't waste your time/money or risk your head!   See my 
> article in /Austin-Healey Magazine/ Nov. 2020 "Get the Lead Out!" Hank
> --------------------
>
> From: "Michael Salter" <michaelsalter at gmail.com>
> To: <healeys at autox.team.net>
> Sent: August 25, 2024 at 8:09 AM PDT
> Subject: [Healeys] Hardened seats in a cast iron 100 head
> I am still using cast iron heads on both my 100's. Amazingly neither 
> have serious cracks as are so common on these.
> I am really picky and don't particularly like the different sound that 
> a 100 engine with an aluminium head makes so would like to continue 
> using these cast iron ones.
> I'm contemplating installing hardened seats in one.
> Hase anyone done this successfully?
>
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