The valve guides on a Triumph TR6 are the shaft that the intake and exhaust valves slide in and out of. The valves should fit snugly inside the valve guide to provide a good seal for the combustion of the fuel and spark. If the guides are worn, then it will cause the engine to smoke excessively, particularly on deceleration. Check your valve guides by sliding a new valve into the valve guides and seeing if you can rock the guides back and forth. If there is any play, the guides should be replaced.
Drain the coolant from the radiator into a suitable container. Remove the upper radiator hose that goes to the thermostat housing and the lower hose that goes to the lower part of the water pump. Unplug the water temperature sensor from the thermostat. Loosen the fan belt with the adjustment nut on the alternator and remove the belt from the water pump pulley. Remove the three 13-mm bolts that hold the water pump on, and remove the water pump.
Remove the valve cover. Remove the rocker shaft bolts and remove the rocker shaft from the engine. Remove the push rods, numbering them from the front of the motor to the back of the motor so that they can be reinstalled in the same order.
Loosen the bolts that hold the head to the motor in the order described in the manual with a ratchet and a breaker bar. These bolts are held on quite tightly.
Remove the head from the engine. The TR6 head is cast iron and extremely heavy, so it is best to have an assistant help in the removal of it.
Remove the valve springs with a valve spring compressor, being careful not to let the valve springs fly off of the head during removal. The valve springs have a tremendous amount of pressure on them, and can be dangerous if not removed properly.
Remove the valve retainers once the valve springs are compressed. Remove the valves, numbering the valves, valve springs and valve keepers so that they can be reassembled in the same order.
Place the head on the workbench, and use a hard steel drift and a hammer to tap (or drift) the valve guides out of the head.
Install the new valve guides with a special valve guide installation tool that presses the valve guide into the head. This is also a job that can easily be done by a professional machine shop for the best results.
Reinstall the valves, valve springs and valve retainers. Replace the head on the motor in the opposite order of removal. Reinstall all of the components that were removed in the opposite order of removal.