Very common exhaust manifold heat exchanger setup. The engine should have a thermostat under the silver ali cover with the top hose coming off it & as I said should run around 80 - 90 degree's. Based on tests done on an Albatross this year (details in the latest CMBA magazine due any day), oil cooling is not required for low rpm river &, as Andre said in him post, is actually detrimental to engine/oil performance in this instance.

If it were me I would loose the engine oil cooler & fit a new thermostat (standard one the engine would have had in the car originally). I suspect you will find there is no 'stat currently fitted.