35.6 x 29.3mm valves in chrome stem with cast iron valve guides. This specification of cylinder head, based on used core castings, is modified in true Road sport style to maximise on-road performance for those wanting maximised drive-ability when used with mild to fast-road camshaft specifications. That means optimised torque out-put through port shape and dimension development and valve throat shapes developed 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. High quality cast iron guides are used along with the latest specification chrome stemmed standard MG Metro valves (35.7mm inlet and 29.3mm exhaust) and 180lb (nominal at maximum valve lift) double valve springs to give a cylinder head capable of withstanding a maximum continual peak rpm limit of 6,500rpm and 0.475" valve lift. Combustion chambers are set at an average 24 to 25cc for big-bore engine use (1360, 1380 & 1400cc). 9-stud fitting as standard. This head has the heater take-off port open and a by-pass hose adapter fitted, both of which can be blanked off for use for 1992-on applications.
A surcharge for non-exchange purchase of £200-00 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.
Some companies call this stage 3 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 exhaust valves and more modified throat and port work
For higher spec race heads ask our technical staff at York or Potters Bar.