I have a SBC 283 and I am troubleshooting a backfire problem, anyhow. I pulled the timing cover off to check the alignment of my timing marks on my crank and cam gears. My question is my cam gear looks like it could be plastic and I cannot see any marks, I also cant see any marks on my crank gear. I know I have #1 at TDC compression but I don't see any defining marks. Any ideas or thoughts? Anyone know of chevy using plastic cam gears?