Konstan's 1982 300D Engine Out Thread

[jt20]

Originally Posted by konstan

#1 is shot as y'all say. What could have caused it? Well, the OIL ring on it was stuck and I had to break . I would speculate that it got stuck because of carbon, and then the piston got scored and it got even more stuck mechanically. What I mean by 'mechanically' is when I got the piston out, the ring groove was distorted enough to bind the ring in one please.

I doubt that this was the source of any kind of knock though. But still, good to fix.

Emery cloth - only to remove larger chunks of carbon. I will give paint stripper a try.

I have a piston from a smaller engine with the same markings. The oil control was broken and half missing, but the second compression ring was stuck.

I also think carbon build up is the answer. As the incredibly hot gases scorch all the oil that is allowed to gather on the sides of the piston and soot is added in, you end up with a big scouring pad.

I do think this could be the source of the knock, though. As the skirts are worn away, the piston is given clearance to wobble around more on the pin. This could definitely cause some piston slap... or the general term 'knock'.

[konstan]

I must've caught it in time, then... the cylinder does not show out of round, using my hole gage and a Fowler vernier caliper...

[kerry]

That's a nasty looking piston. It will be interesting to see how the bore cleans up. I once had a Chevy 283 that I disassembled with the motor in place due to oil burning. I fitted new rings and reassembled. One bore was scored, probably worse than yours but I didn't want to spend the time and money to pull and repair. I probably got another 50-60k out of the motor before that cylinder started fouling plugs frequently.

[KCM]

I would definitely not reuse the #1 piston, it's scrap now. Looks to me that the engine overheated from low coolant. I would also be skeptical whether you can get most of the score marks out of the cylinder wall, which you must to do a good repair job. I'm willing to bet that once you do, you will need an oversized piston as the skirt to sleeve clearance will be way too much. I'm fairly certain this is what was causing your knock, and will cause a knock again with too much clearance.

The other pistons look reuseable, but again, you need to check the piston to sleeve skirt clearance to make sure they are not too loose. You can probably install an oversized piston in one cylinder only and reuse the rest to get by, but to do the job right would mean boring all the cylinders for oversized pistons (or resleeving for standards).

How far you should go depends on how good an engine you want in the end and your budget.

[whunter]

for new members

[konstan]

Originally Posted by whunter

for new members

Lol it was good to get a notification that people find my pics useful!
You will want to see the second thread too:
Konstan's 1982 300D Engine Out Thread (part 2)

[layback40]

Originally Posted by konstan

Lol it was good to get a notification that people find my pics useful!
You will want to see the second thread too:
Konstan's 1982 300D Engine Out Thread (part 2)

Hey konstan,
Its been a while.
How is the car going?
The threads of yours are great reading for anyone thinking of a major rebuild!