TM  10-3930-643-34 ENGINE,  FUEL,  EXHAUST  AND  COOLING  TROUBLESHOOTING  AND  MAINTENANCE.  (cont) 4-4. Cylinder Head Assembly with Valves. (Sheet 6 of 18) DISASSEMBLY/CLEANING/INSPECTION    (cont) 11. 12. 13. 14. 15. Using cleaning solvent P-D-680 and brass wire brush,   clean bores. Do not clean valve guides with a brass wire brush. Blow out carbon deposits with compressed air. Clean valve guides with cleaning solvent P-D-680 and a nylon brush that has a slightly larger diameter than guide I.D. Insert brush into guide and with a turning motion, run brush through to insure removal of gum,  carbon deposits and rust preventive. Clean six exhaust valves-small head (13) and intake valves-large head (14) with cleaning solvent P-D-680 and a brass wire brush. Remove any burrs from stem and grooves with crocus cloth. Dry all parts with compressed air. Inspect cylinder head (6) for cracks using Magnaflux or dye penetrant method. NOTE If cracks are found, cylinder head must be replaced. 16. Using a 9/16” socket and socket wrench handle, install injector nozzles,  thermostat  housing plate, bottom pressure plate and new gasket (7). Plug ports for water tempera- ture and sending switches. Go to sheet 7 4-34