35.7 x 29.5mm 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 brand new twin point injection castings (modified to fit pre-1992 non-injection engines), 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. Both can be blanked off for 1992-on pre injection application.
If somehow the thermostat housing is not machined out to seat the thermostat alternatively you can use
PEQ100650SPACER gasket which gives clearance without machining.
Sold on out-right basis only.
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.