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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