88/16 April ’96
Having stripped, cleaned and prepared the engine for decoke and reground the valves as described in the last month’s article, the engine has to be rebuilt and tuned.
The refitting of the valves into the cylinder head is the reverse of the procedure for removal, using the spring compressor in the same way. Remember to fit the close coils of the spring towards the cylinder head. The valve springs should be checked before replacing. The easiest way of checking a valve spring is by comparison with a new one. Do not be misled by the difference in free length of the spring as this does not always have any bearing on their load at the fitted length. The best way of testing springs is to place a new and an old spring into a vice, end to end, with a flat piece of metal between them. Determine the fitted length of the spring by placing a valve into the cylinder head complete with cotters and caps, but less the spring. Measure the distance between the two faces on which the spring rests. This distance will be the fitted length. Tighten up the vice with the two springs in opposition until the new spring is compressed to the fitted length. If the old spring is then shorter than the new spring this indicates \weakness.
Remove the carbon deposit from the crown (or top) of the piston leaving a ring around the outer edge of about 1/2″. A certain amount of carbon will have formed round the edge of the piston inside the bore. By removing the carbon to the edge of the crown, this ring would be broken which could cause heavy oil consumption. When removing from the top of the piston take care not to damage the piston with a sharp instrument such as a screwdriver. Stuff some clean rag into the openings on the nearside of the engine to prevent the particles of carbon from getting onto the cam followers. The hard carbon will cause uneven wear on the cam followers, which in turn will cause noisy tappets.
Refit any studs which may have come off with the cylinder head nuts and check those in the head for tightness. (I find it much easier to clean the top of the block with the studs removed. Uncle Stan Part) Clean all the flat faces of the cylinder head and the top of the cylinder block in readiness for re-assembling and remove the rag from the cam follower chest. Place the cylinder head gasket on to the top of the cylinder block. The gasket should first be coated with nonhindering gasket cement or grease. (I always use grease. Gasket cement can ‘blow’. – USP) Always fit the gasket with the seams uppermost.
Replace the cylinder head, nuts and washers remembering to use the high tensile nuts and tighten down. Cylinder head nuts should always be tightened evenly, starting from the centre and working outwards towards the ends. If a torque wrench is available tighten the nuts down to the correct torque. (The Mark 1 engine is prone to blowing head gaskets because the studs are too small to allow it to be tightened down effectively. This was fixed on the Mark 2. It is therefore IMPERATIVE that you use a torque wrench, and tighten the nuts down to the maximum recommended setting (46 lb. ft.) in the recommended order. You must also be sure to tighten down all of the head nuts again after 100 miles. Unfortunately, this entails removing the manifolds. But nobody said life was easy. – Uncle Stan Part)
When the head has been refitted and tightened down, the push rods can be replaced. The push rods are better if kept in order. Fit and secure the rocker shaft assembly, making sure the cups of the push rods are located on the ball pins on the rockers. The rocker pedestal nuts again must be tightened evenly to prevent bending of the rocker shaft.
As the cylinder head, valves and rockers have been disturbed the tappets will have to be reset. There are many different ways of setting tappets, the most popular method being the 13 method. Number the valves 1 -12 starting from the front. Rotate the engine a few times to give the valve and rocker gear a chance to find their natural position and check their action. To set the tappets look for the valve which is open, the one where the spring is compressed, subtract the number of that valve from 13 and that will tell you which tappet to adjust. Slide a 0.010″ feeler gauge between the top of the valve and the rocker. The adjusting screw can be tightened or slackened so the feeler gauge is a slide fit between this valve and rocker. Rotate the engine so the next valve is open and adjust the corresponding tappet; repeat this until all 12 tappets have been adjusted.
Place the manifold gasket onto the studs the correct way round; on close examination it will be found the rear stud hole is lower than the front. If fitted wrongly blowing will take place at a later date. Before fitting the manifolds unscrew the nut joining the inlet to the exhaust manifold. Clean off any remains of the old gasket and renew the carburettor joints. After fitting the manifold tighten the nuts and bolts with their retaining plates, tighten the nut joining the two manifolds. Reconnect the exhaust pipe using a new gasket and if the front mounting has been slackened, re-tighten it. Refit the throttle and choke controls to the carburettor and check their correct function, replace the air cleaner.
Either clean or renew the distributor points, setting the gap to 0.015″ when the fibre heel is on the peak of the cam. Clean and reset the spark plugs and if they show any sign of burning on the electrodes renew them. The plugs should be set at 0.025″.
Replace the spark plugs and distributor top. Make sure the correct lead from the distributor top is connected to the correct plug; this is made easier by marking the leads. Re-connect the H.T. lead to the coil.
Renew the gaskets on the water pump and thermostat housing and refit the pump to the head securing at the same time the petrol pipe and dynamo/alternator stay. The petrol pipe can then be connected to the carburettors. Prime the petrol pump with the lever on the side of the pump and examine for leaks. Examine the radiator and heater hoses for cracks or perishing and if necessary replace them. A light smear of grease on the inside of the hoses makes them easier to fit. Refill the radiator and cooling system with clean water, or with the old coolant if it contains antifreeze and has been kept. Examine the radiator filler cap and check the small valve in the centre. Check the seal in the top of the cap.
Place the fan belt around the pulleys and re-connect the dynamo/alternator stay. Pull the dynamo/alternator away from the engine, this will tighten up the fan belt and finally tighten the dynamo/alternator mounting. Join up dynamo/alternator wiring and temperature gauge.
Before replacing the rocker cover oil the rocker assembly and fit a new gasket to the cover. Do not over-tighten the rocker cover nuts as this will distort the cover and cause leaking.
Check that all items have been reconnected and finally reconnect battery. Run the engine for a little while until the normal working temperature has been reached. All that remains is to tune carburettors.