35.7 x 29.5mm race valves in plasma-nitrided EN214N s/steel with manganese bronze valve guides. Nominal 21.4cc with by pass and heater take off holes open.
This specification of cylinder head, based on used core castings, is modified to current fast road style to maximise fast road and track day/weekend-warrior performance when used with fast road and road/rally camshaft specifications. That means optimised BHP and torque out-put through port shape and dimensions and valve throat shapes developed on airflow bench and dyno/rolling roads to work with the aforementioned camshaft types, along with suitable compression ratios given modern lead-free fuel specifications. Genuine AE lead-free exhaust seat inserts are fitted. Latest specification manganese-bronze valve guides are used along with the latest specification plasma-nitrided EN214N stainless steel (35.7mm inlet and 29.5mm exhaust) and 220lb (nominal at maximum valve lift) double valve springs to give a cylinder head capable of withstanding a maximum continual peak rpm limit of 8,000rpm and 0.500" actual valve lift. Suitable for auto-testing, hill-climbs and track day use. Combustion chambers are set at an average 21.4cc since most engines these will be used for will already be using an elevated compression ratio (CR) through either smaller capacity dished pistons and/or larger bore capacities, and their efficiency will boost dynamic CR considerably. 9-stud fitting as standard.
This head has the heater take-off port open and a by-pass hose adapter fitted.
A surcharge for non-exchange purchase of £350 (+VAT in EU)) applies. Heads supplied as exchange units must be in good re-workable condition with no cracks, in completely standard form (no modifications), and complete with valves, springs, top caps and collets.
Road/Rally heads with 29.3mm EN21 exhaust and EN52 35.6mm inlet
C-AHT133 25cc for 1380cc engine
C-AHT135
MSE3 spec with steel valves
C-AHT136 MPI only
MSE6
MSE4 spec no heater take off
Some companies call this a stage 3 head but our way of thinking similar to original Special Tuning is as follows-for 1275 head
Stage1 has 33mm inlet 29mm exhaust std valve sizes and gas flowed
Stage2 has 35.6mm x 29mm ex road quality valves and ported to Road Sport spec
Stage3 has 35.7mm x 29mm ex race quality valves to Super Sport/Grand Tourer spec
Stage4 as stage 3 but with either larger inlet or exhasut valves and more modified throat and port work
For real race use ask our technical staff at York or Potters Bar.