Hey Rob, pistons should be round and the sides should be parallel. The cylinder bores should also be round and the the same size all the way up the bore. The manual should tell you what the correct clearance between the piston and the cylinder should be. Some pistons have a mark on them indicating which way they are to be fitted, this is usually because the gudgeon pin (wrist pin) is slightly offset in the piston.
The wear on the piston in the photograph suggests that the piston is not round and that the clearance with the cylinder wall is too small. Alternatively the cylinder walls are not parallel. Take them back to the shop that did the work and shout at them until they put it right.
Bob
Hi Bob
you might encounter a dispute with the other guys here about the possible oval and parallel shape of pistons in general. I've read there are even barrel shaped pistons, and the oval shape would be normal when the piston is cold. It would get round when heating up. It's all about fractions of mm. When I measure the old pistons, the difference in length and with of the oval would be no more than 0.05 mm (roughly 0.002"), as written earlier.
The Lister LD manual, of a 1 cylinder engine, does mention the direction of the pistons and says it would show the right positioning by the word "Camshaftside" on it.
My old-, nor the new pistons mention any such thing and do not show a mark, or sign. It only shows a number.
When I look into the bottom side of one of the old pistons, I see a tiny desaxation. It could be as little as the thickness of a penny, or even half of that. It goes to the side of where also the number is written at the piston's top.
I understand the function the desaxation (now that I've read about it).
I may have put the new pistons in wrong, both of them with the number at the other side. But could that have resulted in seizing after two minutes running stationairy without load?
I'm waiting for the better manual to be dropped in my mailbox, that's being sent by Jim Perkins from the UK.
It's a pity he had to tell me its a manual of a slighty different model, still... hm. I'll know how 'slightly' when I have it in my hands and see the illustrations.
I wait for that, study the book, before I dare go back to the engine renovation garage to show them what happened. I bought the honing tool and oil, but if honing needs to be done, I may still have them do it.
And yes, I will consult an expert, Matt!
There's one more unusual thing, with this engine: one injector has 4 spraying holes, the other one only three. This was discovered when I had them tested. For the rest, they're identical.