Over the past 35 years we have been modifying the A series cylinder head for our own race engines and supplying them to many other leading race engine builders.
To start the production of the cylinder head a standard 12G940 cylinder head casting goes through a thorough inspection to check the overall quality and suitability for modification. After this process the head casting goes through a crack testing stage to ascertain if it is worthy to be considered for race modification.
Once we have as suitable casting valve sizes are then decided, if the head is to be a large valve offset race head we machine the exhaust valve guide bores oversize to fit offset sleeves, this allows the use of our silicon bronze guides to be fitted but in an offset position enabling a larger valve.
Next we cut the valve seats to the predetermined sizes, we then drill over size holes into the pushrod bores and fit sleeves. Now the hard work starts, both inlet and exhaust ports are fully modified to our flow bench/ dyno proven profiles, once the port modifications are complete, we then drill the cylinder head for the 11 stud fixing and re-face the rocker cover face of the cylinder head.
Now a very important operation often neglected on cheap cylinder heads is to machine the valve spring seat seats to gain an equal height for the fitted valve springs.
After this machining operation we fit our own silicon bronze valve guides, now the head is mounted on our cylinder head machining centre were the valve seats are cut with special 3 angle valve seats to within 0.001
The final manual machining now takes place which is the combustion chambers, these are balanced to 0.2cc. The head is checked for combustion chamber volume then skimmed on our CNC milling machine to give the correct volume. The cylinder head is assembled with a set of our race proven 21NS plasma nitrided valves, race valve springs, new valve retainers and CNC machined collets.