I'm really glad that the Stovebolt forum is available with information and help. My 50 3100 wouldn't be on the road today if it wasn't for you folks.
I have a running 1957 235 engine (sitting on a cradle). I can't drain my coolant. There is some kind of hard black deposit blocking the hole behind my coolant drain plug. It has the consistency of packed graphite. I removed the freeze plugs so I could see inside the water jacket. There's the typical red rust (not bad) but only at the rear of the block (at the drain area) do I see this black deposit. It's a real pistol to get something inside to do cleaning (chipping).
1. Does anyone have an idea what this black stuff is? Carbon? Stop leak? Copper erosion from a radiator? I hope it's not crystallized oil which would mean I have a crack somewhere?
2. From the coolant drain hole to the water jacket, is there a direct path or does it turn left then go up? This would help me a lot to clean out the passage.
There is no water in the oil. Cylinder compression is 130 in #6 and 135 to 150 in the other cylinders. The engine runs fair and probably needs a carburetor kit.
