The first thing to check on used heads is intake and exhaust valve-to-guide clearance. Up to 0.002 inch on the intake and 0.003 inch on the exhaust is less than ideal, but it will work. You can expect the engine to use more oil because of these loose guides since the valveguide seal will not last as long. We checked the clearance with a dial indicator on the valve stem, which gives us a rough idea of the actual clearance. Our heads measured roughly 0.0035 inch for the exhaust and 0.0020 inch for the intakes.