Those motors can have just assume oil pressure. At one point the pressure relief valve was in the oil pump and at another it was in the block. We happened to rebuild a motor once and replaced the oil pump and we got the wrong one. We had no oil pressure relief valve. After a period the gauge in the dash broke and leaked oil. Strange we thought and then it did it again.

We looked at the pressure and cold it would hit 180psi. Eventually we figured it out.

BTW the real early cars had full range gauges and the story I heard was that MB cut the gauge max to basically make it an idiot light. They didn't want people worrying about why on a hot day the pressure would be less than a cold day. They just didn't want concern over quantity of pressure. They wanted a qualitative measure.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician