Cylinder head 4 1/4L deturbulated

The 'deturbulated' description relates to a detail of the combustion chamber design. Deturbulated cylinder heads were introduced on production at the start of KU series chassis.

A deturbulated cylinder head has a lower compression ratio than the earlier turbulated head, but due to better cylinder filling there is no loss of power. For more details refer to this link. At the top end of the engine speed range there is an increase in power if the deturbulated cylinder head is used in conjunction with the pre-M series camshaft.

If fitting high compression pistons it is necessary to use a deturbulated cylinder head. A turbulated cylinder head can be converted to deturbulated by a straightforward machining operation.