When I bought my MG, it had around 37000 miles on the odometer. But the previous owner told me it was actually 137000 miles. The engine “had been rebuilt” at least once by the owner before.

It ran well and I completed the transaction. Over the next 12 years, I put on another 50000 miles or so. I no longer felt the engine was “running well.” It had a bad sound to it. Perhaps a bad timing chain, if it wasn’t for the fact that I had already once replaced that with no change. The timing wasn’t stable, and it was difficult to tune the car with any reliability.

My mechanic would listen to it and shudder at the thought of me driving it to Spokane, a mere 73 miles away. It was time to replace it.

So three years ago, I did. I pulled the engine from my dad’s now parts car, brought it over here, and installed it in my own car. The engine that came with it sat on a stand until I decided it was time to take it apart. It was time to find out what happened to this engine.

All of the pictures below come from the photoset I posted to flickr.

It started off well. Even after sitting for three years, there was no serious rust issues and everything looked as I had left it.

Everything looked nice and clean under the valve cover. There’s some wear you can’t see here, but nothing serious. When I rebuild, I’ll need to replace the rocker arm to correct that wear.

It wasn’t until I got the head off and could look into the engine that the problems started to appear.

The pistons are clean, with oversize marks that indicates that yes, the engine had been previously rebuilt. But look carefully at the piston. Note how it does not sit centered within the piston wall. That’s bad.

But the real surprise came when I removed the cam.

The distributor and oil pump are driven by a single gear on the cam. On my car, that gear was badly worn, resulting in a lot of play. This would give me uneven oil pressure, and it would give me extremely bouncy timing—exactly the symptoms I had experienced.

It would also sound terrible as the car ran.

Still, at least now I know.