Dick and Jim:
I think you will find the belief in the need for lead
substitutes
to be pretty polarizing. Some people swear by it, others think it's a
waste.
I am somewhere in the middle (wishy-washy is my middle name).
There is no doubt that lead in gasoline will protect valve
seats.
The lead is deposited on the valve seat and prevents the hot valve from
bonding to and lifting metal from the seat. There is also no doubt that
many engines have displayed signs of valve seat recession, and this sort
of thing was unheard of when leaded gasoline was around.
There is also no doubt that many motors run just fine without
lead, despite the fact that the metallurgy of the head is vulnerable to
erosion without the protection of lead or something like it.
The question is - how can I tell if I have an engine that needs
lead
or a lead substitute without a teardown? Well, you can't really.
There is always a risk, BUT I believe if you opening your motor
up,
and find no signs of recession that adding hardened seats is mostly a
risk.
That's because you weaken the margin between the valves, and you are
more
likely to develop cracks there. Hardened seats can fall out too,
particularly if the engine ever overheats.
My motor had absolutely no signs of recession at 70,000 miles,
so I
left it alone. I cut new valve seats and that was it. If I keep my
engine
in tune, and don't let the mixture run lean or set the valves
incorrectly
then I believe that I will not see a problem. I think a few egregious
cases have put fear into the minds of the public.
As for determining if your motor needs lead substitute, well, I
would
measure the height of my exhaust valves using a caliper. If any of the
exhaust valves are 0.010" taller than the others, then I would start
using
lead substitute. But then, that's me.
How likely do I think it is that I would find I need to add a
substitute?
On a properly maintained motor with the correct fuel mixture, I would
expect
that one motor in 100 would benefit, maybe less.
Let the mixture go lean, let the timing get sloppy, and the odds
would
start climbing depending on how long the condition was permitted.
Just my demented ramblings....
Vance
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Sally or Dick Taylor
Sent: May 13, 2005 2:27 PM
To: 6pack@autox.team.net
Subject:
Jim---I agree with what you say, with the possible exception on what we
find on the back side of the valves. This heavy carbon caking that is
still present to some degree on the bottom of the valve stems is the
result of oil coming down the valve guides. Even with the no-lead gas
that most of us now use.
<snip>
The same debate is trying to be made for those companies selling
"hardened valve seats, for those engines using no-lead gasoline". I
never bought into this, since I've found no ill effects
with the integral seats and the absence of lead.
Dick
Jim wrote:
This very old issue of "lead" additives being crucial is a crock
designed to sell a product.
<snip>
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