Cylinder covers are thermally highly loaded and are thus subject to wear and tear. If the water treatment (corrosion inhibitors) is not perfect or if the combustion is not ideal (worn out fuel nozzle tip, dripping nozzle, etc) then the wear will be accelerated and additional problems may occur:

  • Heat cracks on the combustion surface
  • Corrosion at the o-ring grooves
  • Cracks in the cooling water bores
  • Damage to the sealing surface of the exhaust valve cage, etc.
cylinder-cover-reconditioning

Depending on the severity of the damage to the cylinder cover, two possibilities exist to bring a cylinder cover back to full working condition. They are called Full Reconditioning and Partial Reconditioning.

Full Reconditioning

Full Reconditioning means that the entire firing bowl is excavated until the cooling water passages lie bare. They are then plugged before the firing bowl is built up again by submerged arc welding. Once this is completed, new cooling water bores are drilled. Full reconditioning also means that new Inconel cladding is applied in the vicinity of the fuel nozzles and that the o-ring groove areas at the outer circumference of the cylinder cover are machined off and are rebuilt by welding.

Fully excavated firing bowl, prior to re-welding
Fully excavated firing bowl, prior to re-welding

Partial Reconditioning

Partial Reconditioning can be applied to a cylinder cover that shows minor defects only. It involves the local repair of small cracks in the firing bowl, the replacement of the Inconel cladding in the vicinity of the fuel nozzles and the repair of all sealing faces.

The cost for fully reconditioning a cylinder cover lies at around half of what a new one would cost. Since there is no difference in performance or expected life time, reconditioning is a very attractive alternative compared to a replacement.

QuantiServ also offers reconditioning of four-stroke cylinder heads.

A properly executed full reconditioning job demands that the entire combustion chamber is excavated to a depth of about 50mm or more and that the cooling bores are welded up and then drilled anew.

If this is not done – and at cheap recon shops it is usually not done – then the cover will in all likelihood crack again soon because existing cracks in the cooling bores have not been removed.

Image Gallery

Cylinder cover machining on a CNC machining centre
Cylinder cover machining on a CNC machining centre
Submerged arc welding of a cylinder cover
Submerged arc welding of a cylinder cover
Partially finished cylinder cover
Partially finished cylinder cover
Another type of cylinder cover under machining
Another type of cylinder cover under machining
Cylinder covers during assembly
Cylinder covers during assembly
Cylinder cover machining on a CNC machining centre
Cylinder cover machining on a CNC machining centre
Localized repairing on a large cylinder cover
Localized repairing on a large cylinder cover