Performance Unlimited Engineering a are an official UK distributor of Darton Sleeves. We not only supply Darton sleeves but can fully machine your block in our machine shop. The machining process involves – The block is loaded into our Haas CNC for initial machining Following the initial CNC machining, the block is placed in the large oven and heated where fitment requires an interference fit. The block is then loaded back into the CNC for decking and boring. Volvo 5 cylinder After the final CNC machining the block is loaded into our Sunnen CK21 computer controlled honing machine with head gasket and torque plate installed (where applicable) The honing process is multi stage and the surface finish tested with our Mitutoyo SF400 surface tester. Honda B16 Evo X Contact us to order Darton Sleeves and enquire about block machining facility.