This, is why you pull the clean out plugs on a crank!

[RalphM]

So I got a chance to attack this today. The first one took a little while trying to figure out the best method. I tried just tapping with a 1/2-13 tap, And putting a bolt in and trying to catch the head of the bolt with a slide hammer hook. It did not work. Then I took a 1/2-13 Bolt and welded it to an adapter on the end of my slide hammer. Also I beveled the hole with a drill bit to cut the swaged portion out. The first one came right out!
A lot of crud hidden in that hole!
Two others were really quick this way. But one still remains.
I drilled it out a little bigger and tried a 9/16 tap and it was a disaster. So I’m gonna have to sit back and think about this one.
The last two pictures show the hole after the plug was removed, I used to pick to pull some of the crud out of the hole.

[RalphM]

Here’s the bad and the ugly.

[Desoto291Hemi]

RalphM,
Back in the mid 80,s I was working in a shop and a Thunderbird came in.
It belonged to a young woman I knew as it turned out.
She had 80,000 miles on it and had never changed the oil.
When she finally did,,,a few days later it spun a rod bearing .
When I removed the valve covers,,,there was a perfect mold of it in wax.
She had used Quaker state all the time,,,,not the oils fault she didn’t change it !

Tommy

[Tony, NY]

Quaker State was (is) a paraffin base oil. Some stories out there of high buildup even with regular changes.

[rotorwrench]

Most oils refined for lubrication purposes are from wells that are higher in paraffin levels. Pennsylvania crude was known to he high in Kerosene or paraffin levels but may have depleted somewhat in the modern era. Paraffin can come from other mineral resources as well. Jet fuel is the most common use for Kerosene now days.

Broken tap removal tools are available or metal disintegration can be employed. A lot of machine shops carry such MDM equipment.

[RalphM]

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Success!
I removed the broken 9/16 -24 tap, Drilled out a little bigger and put in a 9/16-18 tap and while running the tap in and out it just came out!
Now it’s off to the hot tank, but I think I’ll run some wire, and pipe cleaners through first.

[Mart]

I've not done many, but on the 4" French crank in old Rusty I drilled a small hole in the plug and used a coarse threaded self tapping screw to pull them out. I welded the small holes and reused the plugs after, making sure the hole was well peened.

Mart.

[Ross F-1]

Originally Posted by Mart

I've not done many, but on the 4" French crank in old Rusty I drilled a small hole in the plug and used a coarse threaded self tapping screw to pull them out. I welded the small holes and reused the plugs after, making sure the hole was well peened.

Mart.

My rebuilder does it that way, except he doesn't even drill the starter hole. I saw him do a whole crank in less than 5 minutes. He uses an air drill, and a bolt down the middle of an old socket. Practice makes perfect, he probably does 30 flatheads a year.