there is no thermostat and the motor water pump is shut off... I am using the coolant conditioning and water pump of the dyno. that stuff is way over dimensioned. I am measuring the coolant temp in the stock location at the manifold and also using this as input for the temp control of the dyno.

One thing coming to my mind: I do have the oil filter in stock location and some ancient C-body-small block headers where three primary tubes are essentially wrapped around the oil filter (less than 2 inches distance). And I have no real cold air ventilation in that area. Is it possible I am frying my oil there? Especially as I was running a very late spark to show the effects of different COHR in the cylinder pressure trace, NOx emissions and exhaust temp. I had over 1300F exhaust temp in the header tube close to the port.

will post pics on MOnday when I am back at work...

I am currently using a 10W40 Diesel truck oil we are also using on our turbo charger test stand. I know from personal experience (air cooled motorcycles) that these oils in the right motor can handle 140C measured oil temp (about 284F) for short time under heavy load. But it should be no where up there for my understanding in this tame motor!

I have this thing running for a couple of hours now (overall maybe 5), I was thinking if a bearing is making that much heat it would have melted by now...

Do you have an idea how much drag torque these motors should have? Like when you shut off ignition, hold the throttle wide open and spin it with the dyno? That should tell me if there is something so severely wrong...

I cannot really take it apart as I still have to do two classes next week with that motor. Then I can rebuilding it if necessary...

Thanks for sharing your experience! I really appreciate it!
Flo