Inlet Valve 31.0mm (1.22”) dia., EN214N stainless steel Part No: C-AEG588
Exhaust Valve 26.43mm (1.040”) dia., EN214N stainless steel Part No: C-AEG587
Guides HT20 silicone/brass (work hardening) Part No: C-AJJ4037
Valve springs Nominal 180lb progressive rate dual coils Part No: C-AEA526
Stem seals Latest ‘top hat’ design, on inlets only Part No: ADU4905
Chamber volume Nominal 24cc

Exhaust seats Latest spec inserts for lead free fuel Modified to give maximum performance gain for cost. Combustion chambers, inlet and exhaust ports extensively reworked. Stone-ground finish in ports promotes ultimate fuel atomisation. Three angle valve seats in head. Biggest effective valves usable without block modifications and profiles to current maximum flow designs. Combustion chamber volume used to give slight compression ratio increase over standard. A severe increase in compression ratio is generally not needed. The head modifications greatly increase volumetric efficiency, and therefore also increase actual working compression ratio. Gives best results when used in conjunction with a performance cam. Before fitting to engine, ensure block and head mating surfaces are thoroughly cleaned. If fitting to a new/re-machined block, clean surface with cellulose thinners (or other cleaning agent that leaves a non-greasy finish), lay gasket on block, then fit studs. This minimises possible damage to gasket during fitment. If being fitted to an engine that has been running, remove all head studs so block surface can be thoroughly cleaned.

Remove all traces of old gasket, then finish clean with cellulose thinners and continue as above. Arrange pistons so that Nos 1 & 4 are at top dead centre – this minimises loading on valve gear allowing even torque down of head. Thoroughly clean head surface with cleaning agent, then lower down lightly onto block – DO NOT DROP/FORCE IT DOWN, it will damage the head gasket. ABSOLUTELY NO GASKET CEMENT OF ANY SORT IS NECCESARY. The proper A series head gaskets have a coating of lacquer that adheres to head and block faces when hot. Fit push rods and any relevant ancillary studs (rocker gear, thermostat housing, etc.). Back adjuster screws on rocker gear off as far as they will go and fit to head, ensuring push rod cups line up under adjuster screw ball ends. Fit head nuts (and washers if applicable), tightening finger tight, then nipping down with socket in sequence described in workshop manual. Torque down in sequence to 35lb ft first, then to 50lb ft. Torque rocker gear forward studs to 25 lb ft. If no bypass hose is being used, it is essential that the outer ring of the thermostat is drilled in 4 to 6 places with an 1/8” drill to allow water circulation until thermostat opens. If no thermostat is being used, a blank sleeve MUST be fitted. Failure to use either will result in localised overheating of chambers 3 &4 causing excessive heat leading to pre-ignition, detonation, piston failure and cracking of the head. Water pump port must be blanked off (can use CAM4126 and clip 3H2963).

Importation rules regarding vehicles are very specific: Only those over 25 years in age may be brought in to the USA without compilance to Federal Motor Vehicle Safety Standards (FMVSS).