MINI Cooper Forum banner
1 - 1 of 15 Posts

· Registered
580 Posts
Never did a valve job. Had this done at an automotive machine shop.

A buddy of my owned a Wisconsin engine dealership. These were 4-cycle air cooled engines intended for agriculture, oil field, construction, etc. use. They ranged from 1 cylinder to V4s. From 12hp to around 60hp. He sold new ones. But he also rebuilt used one. He made more money rebuilding used engines vs. selling new engines. But the cost to rebuild was less than buying a new engines so customers flocked to his store to get their engines rebuilt.

For the valve job he used a valve seat stone and a valve grinder. The angle of the stone and the angle the valve head had with regards to the valve grinder stone ensured the valve head made contact at the outer portion of the valve seat. The difference in the angles was not large. Less than 1 degree. But contact of the outer edge of the valve head was desired to prevent the outer diameter of the valve head's sealing surface from being exposed to the hot combustion gases.

As the valves heated up the tendency was for the valve heads to give a bit and this then had the valve head making full contact with the valve seat for maximum heat transfer.

He said lapping makes for good contact when things are cold but if the head gets softer from the heat it can have the edge of the valve not making full contact with the seat. If the valve doesn't make full contact it will run hot and this can result in a burned valve.

Now I should stress the Wisconsin engines were air-cooled and thus ran hotter than a water cooled engine.
1 - 1 of 15 Posts