Today was meant to get me to the point I could start the SBC on EFI for spark, but instead I have a big puddle and something of a problem...

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That's where I wanted to put the knock sensor, but sometime in the last 20 years someone else chewed up the plug, and no amount of coaxing was going to get it out. In the end, it ate my 1/2" extractor as well.

So now I have a tool-steel coolant vent. Lovely.

All I can think of is....bummer.....
Probably going to have to remove the motor from the car.

If you are adventurous try the following...... weld a big nut to the plug. The weld won't stick to the cast iron and that might enable you to get it out.

I have done this before with success. I have also cracked a block....so be warned.

block drain,rusted you say?
suck out the coolant,be certain the inside of the plug is not immersed.
first use heat around the plug to burn off any contaminants.
a propane torch will do.
clean physically with wire brush.
re apply heat to cast iron.
allow to cool to hand warm.
apply rustbuster(acetone/tx fluid mix).
or drill out the plug with the correct size.
the plug is npt.

I think you missed an important piece of information.......

Tbrown4x4, which you, and which information?

I don't think veekry9 noticed you have tool steel stuck in your block.

The welded nut idea is a tried and true solution with much success. The heat from welding usually helps loosen things up as well.

You want a nut with an inside diameter slightly smaller than the size of the broken extractor, then plug weld the nut to the broken extractor.

Another solution, depending on access, is using a 1/4" gringing stone in a drill motor to wear into the hardened material.

I recently had a customer break drill bits AND easy outs in his Caterpillar cylinder head. It took four hours, and almost ten stones, but I won.

cool,the easy,not so easy.
as before,then weld the nut on.
probably hard to reach too.

^^^

Agreed. Once the easy out is removed, it's back to getting the remains of the plug out.

I need to try your acetone/ATF solution. I'm a big fan of Kroil, and to a lesser extent, PB Blaster.

Once there is a hardened part stuck where you don't want it, the game changes for the worst!

Would EDM (electron discharge machining) work on the plug?

For those wondering how it turned out:

1) Drifted the remains of the extractor into the water gallery
2) Drilled the plug out to 10mm
3) Cut the top of the plug flush with the block using a cold chisel
4) Used a step drill to work the hole out to 7/16 and taper the remains of the plug
5) Carefully cut the remains of the plug out using a 1/4 NPT tap and chased the threads in the block
6) Flushed the chips out of the block, and fished the head of the extractor out with some wire
7) Generous amounts of teflon goop and the sensor is in and not (yet) leaking

So much for everything else I wanted to do today. But still easier than learning to weld or removing the engine... 8)

Some days just go like this... BTDT...

Great news! I'm glad you got it!

hassle done wit.

Click to view attachment

For scale the table slots are 160mm/6.3" between centers
re+re the shaft +vanes to re-use windings

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2-1/2" tap broken (the other guy).
First rule,DO NOT break the tap.
No heating of shaft,no edm(4130 weldment).
Milled out HSS tap to minor dia.
6"dp/tap cracked/split
time=14hrs.

whatever the reason,things happen.

One thing...in case you don't know. That knock sensor is torqued to only 7ft lbs. If it's too tight it might not work and the engine will ping.

Good job on getting the plug out.

Interwebs says 14lb/ft and water-based sealer; no way to get a wrench on it under the header so it's snug-and-a-bit.

Next adventure is finding TDC and marking something I can see with a timing light...