1. Disconnect the earthstrap from the battery.
2. Remove the bonnet, after first marking the fitted position of the hinges to facilitate alignment when refitting.
3. Drain the cooling system by removing the cylinder block drain plug and/or disconnecting the bottom hose at the radiator.
4. Disconnect the HT leads from the plugs, after suitably labelling them to ensure correct positioning on reassembly. Also disconnect the lead from the water temperature gauge sender unit at the thermostat housing.
5. Disconnect the breather hose (where fitted) from the rocker cover, and remove the air cleaner assembly.
6. Disconnect the distributor vacuum pipe, fuel hose and engine breather pipe (where fitted) from the carburettor. On automatic models, also disconnect the kick-down linkage rod from the carburettor.
7. Disconnect the throttle return spring from the carburettor. Remove the two nuts securing the carburettor to the inlet manifold, detach the carburettor from the studs and place it to one side. Where a cable abutment plate is fitted between the carburettor and the inlet manifold, the plate should be removed with the carburettor.
8. Remove the two nuts securing the heater water control valve, detach the valve and place it to one side with the hose and cable still attached.
9. Remove the nuts securing the radiator upper support bracket to the thermostat housing, and the bolts securing it to the radiator cowl, and remove the bracket .
10. Slacken the clip securing the small by-pass hose to the cylinder head connection, this is located on the underside of the cylinder head, above the water pump .
11. Remove the two nuts, together with their cup washers and seals, retaining the rocker cover, and lift off the cover and gasket . 12. On 1275 GT models, remove the additional securing bolt 'A' and nut 'B' at the ends of the cylinder head .
13. Remove the cylinder head and rocker shaft pedestal nuts, releasing them evenly until the valve spring load on the rocker shaft assembly is released.
14. On models where the ignition coil mounting bracket is attached to one of the cylinder head studs, remove the coil and place to one side.
15. Lift off the rocker shaft assembly, then withdraw the pushrods, keeping them in their installed order.
16. Disconnect the radiator top hose from the thermostat housing.
17. Lift off the cylinder head, complete with the exhaust manifold. If difficulty is encountered in removing the head, tap each side of the head with a hide-faced mallet to free it.
18. Remove the cylinder head gasket and discard it.
Installation is a reversal of the removal procedure, with special attention to the following points.
a) Ensure that all joint surfaces, especially the mating surfaces of the cylinder head and block, are perfectly clean and free from old gasket material.
b) If the cylinder head was removed to replace a leaking or blown head gasket, check the mating faces on both the head and block for distortion before reassembly.
c) Use new gaskets where appropriate. A cylinder head gasket set should be obtained, as this will contain all the necessary gaskets.
d) Do not use grease or jointing compound of any type on the cylinder head gasket when fitting.
e) Ensure the head gasket is correctly positioned. The gasket is normally marked 'TOP' and 'FRONT'.
f) Ensure that the push rods are installed in their original positions. Dip the ends of the rods in clean engine oil prior to installing them.
g) When fitting the rocker shaft assembly, ensure that the rocker arm adjusting screws locate correctly in the cupped end of their respective push rods. If any work has been carried out on the valves (e.g. recutting the valve seats) the rocker arm adjusting screws should be released slightly before installing the rocker shaft assembly. Lubricate the rocker assembly with clean engine oil.
h) Tighten the cylinder head and rocker shaft pedestal nuts evenly, following the sequence shown in . The cylinder head nuts should be tightened in stages to 50 lb ft (7.0 kg m), and the rocker pedestal nuts to 24 lb ft (3.2 kg m).
i) On models which have the ignition coil bracket attached to one of the cylinder head studs, do not forget to refit the bracket before fitting and tightening the head nuts.
j) On 1275 GT models, the additional securing bolt 'A' and nut 'B' must be tightened last. These should be tightened to 25 lb ft (3.5 kg m).
k) Check the valve clearances, as described previously, and adjust if necessary.
l) When installation is complete, refill the cooling system, then run the engine and check for oil, water or exhaust leaks.
m) Finally, with the engine at normal operating temperature, check the ignition timing and engine idle settings as detailed in the TUNE-UP section at the beginning of this manual.
1. Unscrew the spark plugs from the cylinder head.
2. Remove the inlet and exhaust manifolds, together with the hot air intake box .
3. Remove the water outlet housing and lift out the thermostat from the recess in the head.
4. Remove all carbon deposits from the combustion chambers, valve heads and valve ports using a suitable scraper, such as a screwdriver, and a wire brush. Take care to avoid damaging the machined surface of the cylinder head.
5. Similarly, clean all deposits from the cylinder block face and piston crowns, but leave a ring of carbon around the outside of each piston and the top of each bore. Ensure that carbon particles are not allowed to enter the oil or water ways in the block. This can be prevented by plugging the passages with small pieces of cloth while the carbon is being removed.
6. At each valve in turn, remove the spring clip from the collets (early models only). Compress the valve spring, using a suitable spring compressor tool, and extract the two split tapered collets from around the valve stem. Take care to ensure the valve stem is not damaged by the spring retainer when pressing it down. Release the compressor tool and remove the spring retainer, shroud (early models only) and valve spring . Remove the rubber oil seal (where fitted) from the valve stem and withdraw the valve from the cylinder head. Suitably mark the valve and associated components to identify their position in the cylinder head.
7. To dismantle the rocker assembly, remove the shaft locating screw from the No. 2 rocker shaft bracket. Remove the split pins from each end of the rocker shaft, and slide the washers, springs, rocker arms and support brackets off the shaft . Note the relative position of the components for reassembly. If necessary, the blanking plug can be unscrewed from the front end of the shaft to enable the oilways of the shaft to be cleaned out.
Inspection & Overhaul - Valves
Clean the valves and seatings and examine them for signs of pitting, burning or other damage.
A simple method of removing carbon from the valves is to insert the valve stem in the chuck of an electric drill and, using as slow a speed as possible, scrape the deposits off with a file or screwdriver. The valve can then be finished off with emery cloth.
Inspect the valve face and edges for pits, grooves, scores, or other damage. Valves in reasonable condition may be resurfaced on a valve grinding machine, but only sufficient metal to true up the face should be removed. If the thickness of the valve head is reduced to 0.020 in (0.5 mm) or less after grinding, then the valve should be discarded as it will run too hot in use.
Examine the valve stem for excessive or abnormal wear, and renew the valve if necessary.
If the valves are in poor condition, they should be renewed.
Check the stem to guide clearance of each valve in turn in its respective guide. Raise the valve slightly from its seat and rock the head from side to side, as shown in . If the movement across the seat is excessive, this indicates a worn guide and/or valve stem. Repeat the check using a new valve. If the movement is still excessive, the guide is worn and should be renewed.
Remove the old guide by drifting it downwards into the combustion chamber . Ensure the bore in the cylinder head is clean, then drive the new guide into position in the head so that its top end protrudes 0.540 in (13.72 mm), or 0.594 in (15.09 mm) on 1100 engines, above the machined face of the valve spring seating. The inlet valve guide must be fitted with the largest chamfer at the top, and the exhaust guide with the counterbore at the bottom.
NOTE: The valve seats should be recut after fitting new valve guides to ensure the seat is concentric with the guide bore.
Inspect the seating surface on each valve seat in the cylinder head for signs of pitting, burning or wear. Where necessary, the seat can be recut as long as the seat width and correction angle are maintained.
The seating surface must be recut when fitting a new valve, or after fitting new valve guides.
Inspect the bearing surface on the rocker shaft and the bushes in the rocker arms for wear. Two types of rocker arm are used; a pressed-steel type and a forged type . If the latter type is fitted, the arm can be rebushed if worn, but the pressed-steel type must be renewed as an assembly. The installation of the new bushes should be left to a Specialist Machine Shop as they must be burnish-reamed to size after fitting.
Inspect the contact pad at the valve end of each rocker arm for indications of scuffing or excessive or abnormal wear. If the pad is grooved, replace the arm. Do NOT attempt to true the surface by grinding. Check that all oil passages are clear. Replace any damaged or worn adjusting screws or locknuts.
Inspect each push rod for straightness. If bent, the push rod must be replaced - do NOT attempt to straighten it. Also inspect the ends of the rods for nicks, grooves or signs of excessive wear.
Reassemble the cylinder head in the reverse order of dismantling, with special attention to the following points:
a) Assemble the rocker shaft assembly in the reverse order of dismantling. The plugged end of the shaft must be located at the front of the engine. On 1275 GT models ensure that a shim is fitted behind the No. 2 (tapped) rocker shaft bracket, and another in front of the No. 3 rocker shaft bracket . Shims must also be fitted on either side of the No. I and No. 8 (end) rocker arms. On all other models, ensure that the double coil spring washers are fitted at either end of the rocker shaft .
b) Lap in each valve in turn using coarse, followed by fine grinding paste until a gas-tight seal is obtained at the seat. This will be indicated by a continuous matt-grey ring around the valve face and seat. When this has been achieved, clean all traces of paste from the cylinder head and valves - this is most important.
c) Lubricate the valve guides and valves with clean engine oil before installing the valves.
d) Fit new valve stem oil seals over the valve stem and onto the valve guide, where applicable. Lubricate the seal with oil to make fitting easier. On very early models with the valve spring shroud and collet spring, the oil seal is located on the valve stem at the bottom of the collet groove .
e) Ensure that the valve stem is not damaged by the spring retainer when compressing the valve spring, and that the split tapered collets engage correctly in the valve stem and spring retainer when the spring is released. Refit the spring clip to the collet, where applicable.
f) Use new gaskets when refitting the manifolds and water outlet housing.