There are companies who are snowed under with rebuild work !!
450 engine rebuilds ? Most are recon's with 'con' being the main word and contentious point.
Many are in for repairs due to burnt out valves. Repairers wip off the head, clean it up,
put in a new valve and head gasket, tell you it's reCONditioned and that'll be £600 thank
you very much.....
only for the owner to find 6 months later that the reason the valve burnt out was that the
rings on number 3 piston
are still seized in their slots as they were before, and that
oil is still getting past them and onto the valve (oil burns at a higher temp than petrol), and
the new valve has now burnt out and they are back to where they were 6 months ago !
Others are in due to timing chain tensioner failure. The chain slaps about and
cuts/chews into the block and deposits nice metal bits into the oil !
That is usually terminal, but if caught in time can be fixed.....but as the
engine has to be taken to bits to fix it, an complete rebuild should really be considered
as everything else will be worn as well.
A proper rebuild uses new bearings, new timing chain, new tensioner, the head cleaned
up and new valve guides fitted, new valves, and the cylinder bores checked for wear and
ovality for the entire depth of the bore. If within tolerance the bores should be honed till
perfectly oval for the entire bore, and new pistons and rings fitted. Then new gaskets,
spark plugs etc etc, and finally.....if the engine is out, fit a complete new clutch+flywheel
unit and release bearing.
After all, why go through all the rigmoral of lowering the engine and removing the gearbox
6 months later (plus the labour) to fit a new one when you can do it all now ?
Done properly you can give this rebuild (not a reCON) a 12months warrantee.
You'll then know it will power your car for another 60k+ more miles without a problem.
As for the cost, consider all that's involved, including the labour cost to remove and rebuild
and refit...about £1800 complete.
(That's assuming the bores aren't worn so bad that new oversize pistons are required.)
If that sounds a lot, consider that MB charge over £3.5k for a replacement engine, without
any ancilliaries such as plugs, filters, oil, or a clutch.... or fitting !