Darmain
Well-Known Member
Giving you the benieft of the doubt Mdickey666666. This is for your information. If this is known to you then all well and good.
It's not just a case of getting the head smooth, its case of getting it flat as well. Once any remains of the gasket are removed from the mating faces, it is likely the result will be a smooth surface anyway, unless the breakdown area has caused burning and material errosion. When the head is bolted to the block it is important that the holding force by the head bolts is evenly distributed over the mating surfaces, acting through the head gasket. If the head is not flat, within a tolerance, then there will be high pressure and low pressure zones within the gasket. The low pressure zones could then 'blow through', leading to premature gasket failure and you're back where you started. Distortion of the head can occur due to the repeated thermal cycling that the head will obviously experience during normal engine operation. The head bolts hold the head square until they are removed. There is no way you can square the head up by adjusting individual bolt torque levels as there is no way of measuring the surface pressure distribution.
This flattening process can not be done by hand. It must be done using a vertical milling machine, driven by a trained machinest. The machine will literally skim the surface of the mating surfaces so that all areas are at the exisiting low spot levels. The head is then checked using a surface analysing machine to determine the level of flatness error is within tolerance.
Consideration of swarf control must made so to ensure that no swarf is left within the head that could enter the engine. Cleanliness can not be emphasised enough as any material, especially ferris, in the combustion chambers will damage the cylinder walls and ultimately lead to a lack of compression. Such damage will require the liners re-ground, such a major job as to make an engine replacement a serious consideration if this were to happen.
As Laurance says, if the mechanic claims he can, or is intending to do this by hand, then I would seriously consider whether he is up to the job. You don't need an LR specialist to do this, just a competent engine mechanic with a contact with a good engineering works.
I hope this helps.
It's not just a case of getting the head smooth, its case of getting it flat as well. Once any remains of the gasket are removed from the mating faces, it is likely the result will be a smooth surface anyway, unless the breakdown area has caused burning and material errosion. When the head is bolted to the block it is important that the holding force by the head bolts is evenly distributed over the mating surfaces, acting through the head gasket. If the head is not flat, within a tolerance, then there will be high pressure and low pressure zones within the gasket. The low pressure zones could then 'blow through', leading to premature gasket failure and you're back where you started. Distortion of the head can occur due to the repeated thermal cycling that the head will obviously experience during normal engine operation. The head bolts hold the head square until they are removed. There is no way you can square the head up by adjusting individual bolt torque levels as there is no way of measuring the surface pressure distribution.
This flattening process can not be done by hand. It must be done using a vertical milling machine, driven by a trained machinest. The machine will literally skim the surface of the mating surfaces so that all areas are at the exisiting low spot levels. The head is then checked using a surface analysing machine to determine the level of flatness error is within tolerance.
Consideration of swarf control must made so to ensure that no swarf is left within the head that could enter the engine. Cleanliness can not be emphasised enough as any material, especially ferris, in the combustion chambers will damage the cylinder walls and ultimately lead to a lack of compression. Such damage will require the liners re-ground, such a major job as to make an engine replacement a serious consideration if this were to happen.
As Laurance says, if the mechanic claims he can, or is intending to do this by hand, then I would seriously consider whether he is up to the job. You don't need an LR specialist to do this, just a competent engine mechanic with a contact with a good engineering works.
I hope this helps.