From:
voodoo_competition_REMOVE_274310_THIS_@yahoo.com
Frank,
I have heard the horror stories for
years of how unleaded fuel pounds out the seats, wears
out guides and everything else. In reality, I am yet
to see the accelerated wear that people claim.
Keep in mind I spent 2 years in a machine shop
doing nothing but rods and heads.
In almost
every instance of accelerated wear, I can trace the
problem to incorrect seat widths, r valve guide clearance
and/or valve stem seals that were 'too effective' at oil
control.
The amount of lubrication offered by the
miniscule lead content in fuel was negligible at best and
people give it more credit than was due.
Ask a
polymer chemist what role tetraethyl lead played in the
formulation of gasoline and he will tell you everything but
lubrication.
In 1990, I took a tour of the Union 76 Refinery
in Wilmington, California. I asked one of the
chemists there, in charge of quality control, why lead was
added to fuel. He told me this:
"Lead is a
combustion retarder. It raises the octane rating. Nothing
more. People claim it is for lubrication. That is
false. You should see the wear exhibited on some of our
pumps that are submerged in gasoline. I see the same
amount of wear now, with unleaded fuels, that we had
with leaded fuels."
My 429 Ford ran very high
spring pressures and had OEM seats, ground right into
the head. I cut exhaust seats to .080" in width and
intake seats to .060" both centered on the
valve.
I drove that car for 80,000 miles and made
countless dragstrip passes. When I sold it in 1998, I
disassembled the 429 SCJ and replaced it with a 460. I sold
the parts individually on E-Bay because I didn't want
anyone to end up with the complete motor.
That
11.25:1 429 made 430 horsepower at the rear wheels and
killed the C6 Automatics with regularity. The 4400 pound
car ran 13.80 @ 106 all night long and would do it at
100° or 75° temperature. It made no difference
whatsoever.
The heads looked so good when I removed them you
would not believe it. The seats were still very narrow
and the guides were still tight.
I think
your heads will be just fine. One thing to keep in
mind is valve stem seals. On a Chevrolet, all I ever
use is the stock 'O' Ring seal. I have never had an
oil control problem if the guides are sound.
The only other seal I would use would be the very
small 302 Ford Umbrella, but I don't like them as well
as the 'O'Ring.
People can use what they
want, but for longevity, I think Teflon Seals are too
good and deprive the stems of necessary
lubrication.
Make sure your seat widths are narrow and well
centered on the valve. You will enjoy many thousands of
miles from them with no troubles.
Also, with
respect to 'pounding' of the valve seats. I have only
seen this a few times and in each of these cases, I
noted weak valve springs and high rpms that caused the
valves to 'bounce' off their seats.
Be sure you
have the correct springs for your camshaft and always
less than 300 lbs. open pressure on a flat-tappet
street engine.
I hope this information is
helpful...Robert
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