l'IvIrIIrrvfvvvv---._ THE ENGINE A Completely unscrew the eight rocker shaft bracket nuts and remove the rocker assembly, complete with brackets, and rockers. Withdraw the eight push-rods, storing them carefully so that they may bereplaced in the same positions. To dismantle the rocker shaft assembly, rst remove the grub screw which locates the rocker shaft in the rear rocker mounting bracket and remove the split pins, at washers, and spring washers from each end of the shaft. Slide the rockers, brackets, and springs from the shaft. Unscrew the plug from the front end of the shaft and _ clean out the oilways. Reassembly and replacement is a reversal of the above procedure, replacing the rockers and springs in their original positions on the shaft. Remember to replace the rocker shaft locating screw lock plate. Replace the rocker cover with the vent pipe to the front. Check that the two cap nut rubber bushes and the rocker cover cork gasket are undamaged; if they are found to be faulty, t new ones or oil leaks may result. Retting rocker bushes To remove and replace worn rocker bushes the use of Service tool 18G 226 is recommended; the bushes and the rockers can be very easily damaged by using improvised drifts. Place the rocker on the anvil and drive out the worn bush. Place a new bush on the driver and position the bush with the butt joint at the top of the rocker bore and the oil groove in the bush at the bottom of the rocker bore as shown in Fig. A.3. It will be necessary to drill the oil holes in the bush to coincide with the oilways in the rocker. The oil hole to the adjuster end can be drilled before the bush is tted, extra care being taken to keep the holes of the bush and rocker in line during the pressing-in operation. If the holes are drilled after tting, the following procedure must be adopted. Remove the adjuster screw and use a -093 in. (2-36 mm.) drill to drill out the end plug and to continue the oilway through the bush. Replug the end after this operation with a rivet (Part No. SC 2436) and weld the plug into position. The oil hole in the top of the rocker barrel must be continued through the bush with a No. 47 drill, -0785 in. (1-98 mm.). ailn Q in... in... o no no 0 O o 000 pogo o o AD1325W Fig. A.2 Cylinder head nut slackening and tightening sequence MGB. Issue 6. 25729 lut - :3 H Y 77 , Fig. A.3 Showing the correct position for a valve rocker bush A. Oilways. 8. Joint in rocker bush. c. Oil groove. Finally, burnish-ream the bush to the dimensions given in the GENERAL DATA section. Section A.6 CYLINDER HEAD ASSEMBLY Drain the water from the cooling system. One drain tap is at the base of the radiator on the left-hand side and at the rear of the engine on the right-hand side. On later 18GD and 18GG engines the cylind ':;;_block drain tap is replaced by a removable plug an; Sealing washer. If anti-freeze mixture'tis being used it sh0uld be drained into a suitable clean container and carefully preserved for future use. ' Remove the top water hose. Remove the three thermo- stat housing securing nuts and washers and remove the housing and thermostat. Remove the air cleaners and carburetters as detailed in Section D. Remove the inlet and exhaust manifolds as detailed'in Section A.4. Remove the rocker assembly as detailed in Section A.5 and remove the seven external cylinder head nuts at the same time. Withdraw the push-rods, keeping them in the order of their removal. Disconnect the high-tension cables and remove the sparking plugs. Disconnect"~the heater hose and heater control cable from the water valVe, Unscrewilgthe thermal transmitter from the front of the cylinder head and release the conductor from its supporting clip. Slacken the clips and disconnect the hoses from the water pipe on the left-hand side of the cylinder head and remove the pipe. Release the ignition vacuum control pipe from the rear cylinder head stud and remove the cylinder head. ~ Break the cylinder head joint by levering at one end and withdraw the head evenly up the studs. . A.5