I recently purchased a 77 450sl. The exterior and interior and pristine, which would be even more outstanding if the engine wasn’t seized but I was able to get it for a good price.

The previous owner said that he had a new fuel distributed installed and had the oil changed. He drove it home and then then next time he went to start it the engine was seized. He didn’t report it having been overheated or having ran out of oil. Nor does it appear the oil was diluted with coolant or water (based on the oil left in the valve train bolts and nooks and crannies). The car had been garaged and not left out in the weather.

Since I have had the car, I have removed the spark plugs and soaked the pistons. I have removed the starter with the thought that the starter might have been stuck in the flywheel. I also removed the belts in case any of those components were stuck. However, so far, I have not been able to get the engine to budge by turning the crank via the crank bolt.

I took off the valve covers and the timing chain seem tight and chain guides are in place and not broken. The cam lobes look ok and there doesn’t seem to be any obvious signs of being ran without oil. I don’t see any obvious signs of trauma to the valve train.

We have pushed the car into the garage, so I don’t think the torque converter is stuck.

Is there anything else I should be looking at? From what the previous owner said, it seems strange that the engine would be locked up. Is it possible that sometime might have dropped down in the engine and caused some interference? If so, where would I look?

Any help for suggestions would be appreciated!