^^^Two comments I was hoping not to hear.

Sounds like it was just about that length.

I would verify before doing anything drastic. Blow compressed air in the drilled glow plug. If it holds pressure, you only have a glow plug to remove. Otoh, if you get bubbles in the coolant tank....... my condolences.

Thanks for the suggestion. But I don't have the time, means or funds to go where this route would lead me. Time to say goodbye to her and hope someone with access to a machinist or a means of replacing the head can keep her alive and running. :(

Going to miss this car.

I would love to get this car, as I think I can fix it whatever the problem is. However, I might as well be on the other side of the planet being in CA!

Do not crank the engine until you have ruled out breech of coolant jacket. potential hydro locking!

If I had done this, here would be my "on a super tight budget, need to get her running with nothing much to lose" attempt:

1.) Thread GP and remove.
2.) Inspect with $8 USB inspection camera
3.) If there is a hole in the head into the coolant passage, drain coolant.
4.) since GP is now removed, the ID of the hole is now significantly larger than the drilled hole diameter.
5.) Look at a drill and tap chart and select a common tap that matches the hole you punched into the coolant jacket.
6.) Hand tap the hole into the jacket.
7.) Degrease the threads, install a set screw with lots of threadlocker (heat resistant type? Coolant on one side of the screw should help keep it intact?)
8.) Let it cure, refill with coolant, pressurize cooling system, inspect with camera for leakage.
9.) if no leaks, button it up and hope for the best!

I'm not a machinist, just an engineer that gave it a little rent in my head last night...so take with a grain of salt.

This is a very interesting suggestion. But a few things to note:

#4 - GP is still not removed. It may be virtually gone by way of me continually drilling with larger and larger drill bits at this point. But I haven't actually removed anything other than shards and shards of metal shavings.

#6 - Do you really think this is possible? I mean taps are short. There's barely any room to work in there as it is. And based on comment above, I apparently drilled over 2" into the head. I mean I couldn't properly tap the center of the GP. I don't trust my skill set to tap into those depths.

I like your thinking and I am intrigued. I'll try anything.

First, drain the coolant ASAP to keep it from slowly leaking into the oil pan.

Grab a borescope from Amazon prime and have a look inside.

Amazon.com : 2 In 1 Smartphone USB Endoscope Inspection Camera, CrazyFire® 5.5mm Android Borescope USB Inspection Camera, Waterproof OTG Micro USB Borescope Inspection Camera with 6 LEDs and 5m/16.4ft Cable : Camera & Photo

You can get long taps:

Union Butterfield 3306E(UNC) High-Speed Steel Thread Forming Tap, Extra-Long, Uncoated (Bright) Finish, Round Shank With Square End, Bottoming Chamfer, H9 Tolerance, 4" O'all Length, 3/8"-16 Thread Size: Amazon.com: Industrial & Scientific

These are the screws I was imagining:

https://www.fmwfasteners.com/products/3-8-16-x-3-1-2-socket-set-screw-cup-point-alloy?gclid=CNC93paMh8wCFYeUfgodYIYP3A

Have you tried a leak down test of the glow plug first? It's easy to do and will tell you instantly if you have breached the coolant or not.

If anything, take a deep breath and take your time with the solution. Anything can be fixed, and many "holy sh&* moments are readily fixable and no big deal.

renaissanceman - TY for the tips and the links. I will consider this as an option. I have an Apple phone, but I can find a comparable borescope now that I know what I am looking for.

I don't know what this is.

You apply compressed air into the drilled glow plug and look/ listen for bubbles in the coolant expansion tank.

So, regards the GP drillout; is a helicoil installation, part of the possible plan going forward?

At what point do you, (generic you) go with a new head assembly?

Just trying to explore your ultimate options going forward on completely solving this job.......

depending on where this thing broke off (I think the threaded portion came out, leaving just the long shaft on the GP?) would depend on whether the threads would need to be reconstructed.

I'm going to venture a guess and say that a leakdown would be pointless...if there is coolant pouring out, the jacket has been breached. At this point the injector needs to be pulled, and a scope inserted through both the GP and injector holes to asses the damage. From there, post up the pictures and we will all mull over the best solution.

If the only alternative to an unconventional repair like I detailed is replacing the head, which the OP says is not an option, then we should get creative! If nothing else, we will gain knowledge of what the options for repairs are as this type of thing becomes more common as more GPs fail in the 606 engine out there.

Let's define ASAP. My drill aggressiveness occurred Yesterday Morning (Sunday). It's been over 24hrs, and realistically I won't have time to touch this thing again till Saturday. Is that too long?

If I am courageous enough to attempt your method I will just change the oil if that set screw plug holds pressure.

As far as draining the coolant. Will it be sufficient enough to pull the radiator plug? Or do I need to pull a plug on the block too (Does this car even have one?) If so, I need to find that.