From an article in the July 29, 1937 issue of "Farm Implement News", MM Chief Engineer A. W. Lavers had this to say about the new Model Z's engine. "It has literally 140 less motor parts, and it can be serviced from a milk stool with no drip in the eyes. In fact, you can put the Z in the parlor and it won't smear the rug. It has no oil pan at all. The crankcase is one solid casting without a gasketed joint below the plane of the shaft." He goes on. "How is an engine serviced from a milkstool? Sit down on your stool with a suitable wrench, back off the bolts on the camshaft side of the block and two plates come off. Before you are the connecting rod bearings and the tappets for any needed adjustments. Go around to the other side, sit down comfortably, remove those bolts and off comes the spark plug cylinder head cap. And, there are your valves open for grinding."
These engines were designed to be easily serviceable and repairable by the farmer who owned one. They have also proven to be very durable. I still have the tractor I grew up on. It's a 1950 ZA. When I overhauled the engine last year, the cylinders and pistons were still standard bore and within dimension. New rings restored the compression and I pull it in antique pulls, 60 years after I drove it plowing the fields.