Timing Chain Guides

[Hyundai Respecter]

I don't think that's correct. One pulley for each cam is common for DOHC with timing belt.

Hyundai Beta II engine had the timing belt driving the exhaust cam, and a chain driving the intake cam

 

[350Rocket]

And older yet some times phenolic was used to make gear teeth in some gear drive setups, the only reason to use non metal in those applications was to try to make the engine quieter for some fussy goofs. The non metallic gears and sprockets had low durability, and pretty much destined to fail at around 100,000 miles so maybe that was also part of the plan as well.

Yeah, I don't get it because my 350 olds has steel gears in it now and I sure don't hear any noise from it. But that was the idea apparently. I did get 160k miles out of the original ones on an 87 Caprice with the olds 307. They were beginning to stress crack but hadn't failed yet. I didn't them because I was doing the water pump.
The original gears in my 76 350 looked identical. Stress cracks starting but nothing broken off yet.

 

[SC Maintenance]

And older yet some times phenolic was used to make gear teeth in some gear drive setups, the only reason to use non metal in those applications was to try to make the engine quieter for some fussy goofs. The non metallic gears and sprockets had low durability, and pretty much destined to fail at around 100,000 miles so maybe that was also part of the plan as well.

Ford did the same thing in their later inline 6's - like the latter 300-6's in the 80's. Ask me how I know (As I coast to a stop in BFE)

 

[Greasymechtech]