The Stovebolt Site Forums The Shop Area Engine Shop 235 block drain plug

My 1947 3100 has a 1959 235 engine. I removed the 13mm drain bolt on the lower left side with intentions of draining and cleaning the block. However, nothing came out. I tried to push a small punch in the plug hole and apparently it is frozen up with gunk because it won't go in. Would it be safe to use a drill and a small drill bit to get it unplugged? Also, when I tried to screw the plug back in it just would not screw back in. I will say it took quite a bit of torque to remove this plug. Thought about putting the plug in freezer overnight to see if it would help. I would appreciate any suggestions from anyone else who has had this issue.

Yes. No problem doing that. Is the engine on a stand?

You can use a pressure washer to get all the way in there to blast out the loose crud. Evaporust, CLR, and other , similar products do a great job cleaning out a crudded up engine.

Run a thread tap through the hole before putting the plug back in.

You can also knock out all the core plugs to gain access to help clean the block. They can be replaced with rubber expansion plugs if you don't want to pound brass ones back in.

Be careful when you go to put it back together.

You made the comment that it is a 13mm bolt. Nothing on these old trucks should be metric. If you go to chase the threads, make sure you use the correct american tap, not a metric one.

My recollection is that should be a 3/8" NPT thread, but I am not certain, so I would recommend double checking

The drain is 1/4” NPT. A drill as long as you’re not too aggressive would work. It may not clear the blockage but it’s a good place to start.

I used a stiff wire as then you can bend the wire .I think going straight in from the hole you will just hit the cylinder wall I remember cleaning up and to the back from the drain hole

You can get aggressive with a skinny screwdriver and a hammer into the drain hole to start to break up the clog.
You should be able to get some water to trickle out. That's a good starting point. If you cannot get the water to trickle very much or not at all, you may want to chase the threads with a NPT tap so that you can put the plug back in and drive it until it's time to remove and completely disassembled the engine to do a thorough cleaning of the water jacket.
Who knows how many doses of stop leak Farmer Bob put in there to stop the radiator from leaking over the years.
Whatever they used back then turns into asphalt and is difficult to break up even once you tear it down to a bare engine block.
I haven't found any solvent of any description that will dissolve that stuff.
As long as the engine isn't running hot, I'd continue to drive it as is.

I just finished chasing the threads and installing a new Edlemann 1/4 NPT petcock. For now I just left the hole stopped up until I can get the truck on a lift for better access. My truck is still stock except a previous owner replaced the 216 engine with the 235. Thanks, ray durham

You can also plumb an air hose to the block drain and use compressed air to blow the crud out of the way. Just be sure to remove the radiator cap to prevent destructive pressure from building up in the cooling system. Once a somewhat clear drain path is established, some aggressive flushing can be done with various chemicals.
Jerry