OMC Stern Drives And Motors 1964-1986 Repair Manual., Page 50Get this manual
GMC INUNE
Critical valve tolerances
t valve from side-to-side, with light pressure obtain readingIf the exceeds 0.001" the 0.002" for the exhaust, will be necessary ream the valve guides for oversize valve stemsValves with oversize available for inlet and exhaust valves in the following sizes: 0.003", 0.015", and 0.030ttUse the 38" reamer sizes from Tool 3-7049 which are: J-7049-7 Standard; 3-7049-4, 0.003" oversize; 3-7049-5, 0.015" oversize; and 5-7049-6, 0.030" oversize ream the bores for new valves
A severely burned exhaust valve faceThe valve was sticking in the guide as evidenced by the gum on the neck of the stemT TIME clean the valve guide thoroughly