...The very rare and now extremely expensive 917 oil-thermostat. Note the larger oil passage ports which flow approximately 33% more oil volume (needed for the 4.5 liter and later even bigger engines). Since the oil-lines used by the 917 were in fact larger than anything else used by the 2 liter flat-six engines, the 917K oil-thermostat naturally had to be made a bit bigger.

I just recently found this piece, take a look...