When a petrol or diesel engine overheats, usually from a lack of coolant caused by things such as water pump failure or a radiator leak, the cylinder head often becomes distorted or bowed. If this cylinder head is refitted without being refaced or skimmed, then the repair will often fail and the head gasket will not be properly compressed and a sufficient seal will not be created.
The operation of skimming the head creates a new flat surface and removes the risk of future failure.
In a modern engine, the tolerance of the cylinder head should be less than 10 microns (or 3 thou in old money). This fine tolerance is because the head gaskets used in modern engines are usually multi-layered steel gaskets, which are much thinner than older style head gaskets and require much greater accuracy.
Our in-house team can also address the issue of corroded or pitted aluminium heads by first conducting a welding repair to fill the pitted area, and then skimming the head in the usual fashion. Please note that currently, we are only able to skim aluminium heads. We do not have the facilities to skim cast iron heads.
Most petrol engine cylinder heads can be skimmed with the valves left in place and just the camshaft or rockers removed. For diesel cylinder heads, the valves generally sit proud and will need to be removed prior to skimming. The valves can be removed by you, the customer, or by us (we do charge for this extra work if required).
Our milling equipment has the largest and widest bed we could source and we have yet to meet a head wider than we can cope with. We do offer a local collection service for those who are swamped with work, and we are always keen to help.