Just installed a replacement M3 engine, first start tonight.

It runs with good oil pressure... but when cranking it sounds very "clanky" for want of a better word. The regular "thump thump thump" of cranking has a more clangy sound to it.

Could this be due to fitting a lightweight flywheel instead of the dual mass? It doesn't sound like my old engine did which died of big-end failure (I did the big ends before installing the new engine and didn't see any badly worn bearings or crank damage).

Youtube link: http://www.youtube.com/watch?v=O7ST5sXwJP4&feature=plcp

Could be engine hitting the chassis?

yep, sounds like its hitting the frame or a panel somewhere.

Took the afternoon off to work on the car and get to the bottom of this... Found a bit that was very close to the chassis, so I sorted that out with a hacksaw, then started the car... and the starter did absolutely nothing.

Cue FOUR HOURS of tracing wiring and cursing... and then it started working for NO REASON AT ALL (ok maybe the battery was a bit flat but I'd have expected something from the starter).

And then I found that the engine's actually in firm contact with the chassis somewhere else (on the sump). So in summary I've taken the afternoon off to solve this noise and achieved zip. Bloody cars.

Check all your earths. I had a slightly loose earth once and it gave me the same intermittent symptoms.

Will do, thanks, I guess the engine block - battery earth path is the most critical?

It certainly is as far as starting is concerned!

Yup, engine was touching the chassis. Fixed now and it sounds healthy again. Phew.