"My `68 Ford wagon 302-v8 had plastic coated timing chain gears (or maybe only one of them). A small bit of plastic (grain of rice) dislodged after the plastic became well old and brittle. That little grain was sucked up into the oil pump which caused the oil pump gears to stop motion and thus the pump's drive shaft to break - instant and 100% valid low oil pressure light with a car at the side of the road."
Those plastic coated timing chains were common in the late 60s-70s and caused a lot of issues, albeit after high mileage usage (100k in those days). My 78 sbc probably had that originally (I still have have the timing chain I pulled out in a box - I should see what it is). They seemed to stretch a lot as well - and the one I took out was definitely stretched. The 70 v6 in the cj also had one from the factory in those days. I think the idea was the plastic was a sort of low friction, low wear idea, but not sure plastics engineering was up for it back in the day. Both the v6 and this v8 have all metal replacement chains - but I kept it simple as single chain design, not double chain set-up. There are also aftermarket timing gear sets that eliminate the timing chain all together and just use a 3rd gear between the crank sprocket and cam timing gear. Lots of cool stuff out there. The 58 project as a whole has worn me out, and some of the hassle hasn't probably been worth it, but the engine build was something I have been looking forward to, and its been great so far. As long as I don't trash the cam during start-up and break-in...