I'm currently doing by first engine rebuild on a 3.9 with an interim block. I though I'd check for bore wear by inserting the pistons upside down and seeing if there was any sideways movement. There was a small amount in one direction but a noticeable amount more in the other direction which I assumed meant the bores were slightly oval. But if I turn the piston around 90 degrees the extra movement moves with it suggesting the pistons are slightly oval. The greatest movement is in the same direction as the gudgeon pin.
Measuring the pistons seems to indicate they're perfectly round and I can still see the lines in the piston casting that go all the way round, again suggesting they're not worn.
The rebuild manual says the pistons should be 0.018 to 0.033mm smaller than the cylinder bores so I thought there should be virtually no movement.
Has anyone else found the same problem? Is it likely to be down to the bores?
Thanks
Measuring the pistons seems to indicate they're perfectly round and I can still see the lines in the piston casting that go all the way round, again suggesting they're not worn.
The rebuild manual says the pistons should be 0.018 to 0.033mm smaller than the cylinder bores so I thought there should be virtually no movement.
Has anyone else found the same problem? Is it likely to be down to the bores?
Thanks
