4/25/08
Valve Trains
François' got a 250 PF Coupe engine on the engine stand for a
rebuild. François likes to do engine rebuilds in the evening
when the phone stops ringing and there are no distractions, so progress
moves forward after I arrive at his shop!
I was put to the task of fitting some of the valve train components.
New valve guides will be installed, and the steel spring shims had to
be fitted to each guide. The guides are just a couple thousandths
thicker than the inner diameter of the shims, so I had to chuck them in
the lathe, and take a little material off each guide until the shim
passed freely. This will insure a good fit when the valve springs are
bottomed out on the top of the head.
I also cleaned, inspected, polished, and reassembled the rocker
assemblies, making sure everything was well oiled and operating
smoothly. With multiples of 12 for every part, I was kept busy for most
of the day!
We pulled Art Suckewer's Series II 330GT 2+2 into the shop for some
diagnosis this week. Art is an owner and Tomyang.netter that had some
problem with his car sometime after the Fall Party. He described a
knocking noise from the engine, and decided it was best to have the car
towed to François' shop.
Art has had an intermittent smoking problem with his car as well, and
it was time to see if we could find the proverbial smoking gun.
Unfortunately, after disconnecting the fuel line, removing the spark
plugs, ignition wires, and throttle linkage, we removed the valve
covers to find everything in order. One area François wanted to
check was the timing chain tension, but he found it to be tight with
very little play. Nothing was loose or rattling, but when we removed a
rocker assembly, we found a problem.
All the exhaust valves showed excessive wear at the top of the valve
stem. A tappet presses on this area to open the valve on every cycle of
the combustion process. Both surfaces are hardened, but once the harder
surface of the steel is worn away, the softer steel is worn at an
exponential rate.
Most of the intake valves were in decent shape showing normal wear.
Further inspection of the valve guides and seals could explain the
smoking, but we were disappointed there wasn't something to show Art
that could explain the noise. Another possibility could be a
broken piston ring, but that inspection would be even more involved.
Unfortunately the wear on the exhaust valves has to be addressed sooner
than later. If this kind of damage continues to happen, catastrophic
damage could occur. The top of the valve stem could split, and the
spring retainers that hold everything together could let go, dropping
the valve into the combustion chamber.
Just a reminder, I'm looking for a
new Vintage Ferrari Project. If you have, or know of a restoration
project, please let me know. It would be great to restore another car
on this website! My E-mail.
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