I bought this 740 turbo a few weeks ago. The engine is a transplant because the original one had seized due to no coolant. Generally speaking the car runs fine, has lots of power, and tight steering and suspension.

A little hard to start though. It stumbles for a couple of minutes on real cold mornings. Whether its cold or warm though the engine always makes lots of noise which seems to be coming from the valve cover area. The noise is a lot like what a diesel engine would sound like. It doesn't do very good on the jiggle test either although the breather box and hoses aren't clogged.

I've been through the engine compartment pretty thoroughly to eliminate vacuum leaks, intake and exhaust leaks, etc. I keep thinking that if I look in the right place the cause of the noise will be obvious to me.

So, where should I start?