Engine liners

[Bar1092]

Can any one tell me all of the dangers of getting the piston liner hieghts wrong
On a six cyl merc axor truck engine. ( 6 individual heads)

[Rockster]

Bar1092 said:

Can any one tell me all of the dangers of getting the piston liner hieghts wrong
On a six cyl merc axor truck engine. ( 6 individual heads)

Well, generally they do not want to be wrong. The cylinder liner wants to be flush with the top of the block or in this case flush with the top of the cylinder and to ensure this a skim cut is sometimes taken that removes just a tiny amount of metal from the deck of the block or the top of the cylinder and at the same time removes a bit of the liner sticking up so after the machining operation the tops of the liners and the deck of the block are in the same plane. (The heights of the cylinders want to be as close to the same as possible too.)

If the liner sticks up too high the cylinder head will not form a water, oil, combustion pressure tight seal and there'll be leaks at least. In more severe cases the head bolts will not have enough thread engagement and if you attempt to torque these the threads in the block will pull/strip.

If the liner is low this puts the head gasket at risk as the surface area of the gasket forming a seal is reduced and a cylinder and cylinder head gasket could (will) leak.

If the liner is too short at the bottom it may not support the piston sufficiently at the extreme end of its stroke.

If the liner is too long at the bottom the crankshaft may make contact under some operation conditions.