The Stovebolt Site Forums The Shop Area Engine Shop 1959 Apache 3100 283 cam gear Q.

Working on resealing oil leaks and a major leak was the timing cover. I removed it to discover a loose timing chain, but what really surprized me was the cam gear has nylon teeth! I was told the engine was original, or at least the heads were and to be sure and use lead additive because the valve seats were not hardend inserts but milled original heads. I was thinking that nylon gears were not introduced until the late 70's, and only GM until they figured out they were prone to breaking ect. Am I correct to think that the nylon gear means the engine is possibly a replacement? Nobody would replace a timing chain and use a nylon gearset?? How would I determine the valveseats are original without removing the heads themselves? Is there a serial number under the valve covers much like my old small block ford? This is my first SBC to ever get my hands on.

Thanks RK

The original timing gear would have nylon teeth, aftermarket gears would be steel. GM used nylon gears to reduce the noise on the timing chain, they started with those in the early V8's (60's) and continued for most of the Gen 1 small block run. Your engine should have stamped numbers on the block just in front of the passenger side head. That number will give you the build date and designation (car or truck).

I would not say you had to use hardened valve seats unless you plan on some pretty severe use (towing, racing, etc) or doing something like running it on natural gas or propane, but I can't say somebody won't show up to tell you that you do need them. If it were me, I wouldn't worry about it.

I'm pretty sure P.T. Barnum originated the "use lead additive" advice. It's a good way to transfer money from gullible people's pockets to the people who sell that stuff. Unless you're running some sort of super-dry fuel like LP gas of CNG, there's no reason whatsoever to worry about having hardened exhaust valve seats. Your engine is in a lot more danger from an incorrectly-installed seat coming adrift and wrecking it than any problems that might happen with erosion of the original seats.
Jerry