is my M42 dying?

[shutter]

Sounds pretty similar to this guys car below, which ended up being his timing chain. I know a tensioner stopped the noise for him, but he ended up rebuilding the whole thing. Pretty sure that you're going to have to the same, not cheap, even if you DIY. Chain, guides, etc... +waterpump and thermostat while you're in there.

Yours is knocking a bit, could be the chain caused some more damage. Good luck, doesn't sound healthy!

http://www.youtube.com/watch?v=SWIny3cKHrg&feature=related

[LivingLegend06]

Any additional input would be appreciated.

To me it doesn't sound at all like the video that shutter posted.

[Van Westervelt]

We have given input. Now go investigate, and report back.