Dale: Valve recession is the distance the face of the valve head is from the face of the cylinder head especially on the intake valve. The exhaust can be measured after the intake valves are set correctly. In 1961 Oliver came out with a kit to correct the proble. The head needs to be removed and then the head needs to be machined for valve seats by a machine shop. In case you can not find the correct adaper and a diesel compression tester you may want to take a cylinder leak down test.  It will not tell you how much compression you have but it will tell you if you have rings and valves that are not sealing the compression. Five minutes is not enough to warm up the engine. Questions?