My Project Thread. 88 350, my first idi.

[bumblebeer]

Is there enough threads left that you can clean them up? I don't know the thread pitch, but maybe you can use a thread restorer and still have it hold a glow plug into place.

Could a helicoil be an option? If they are available in that thread size if the threads in the head are too far gone. May not even be an option, just a thought.

James

Unfortunately helicoil isn't going to be an option. I done goofed it up real good. Who let me have access to power tools anyway???

I did finally get the EZ out, well... out, by eating away at it with a (multiple) diamond coated Dremel bits. After it was removed, I got to work drilling.

I started with a bit that was about the same size as the inside thread diameter of the glow plug. Although I was able to drill down a little past the threaded section, I was not able to pick out what was left of the glow plug threads. I believe they got married to the sides of the hole at some point during my welding adventures.

So then I went with a 13/32 bit cause I believe that is damn close to the correct size to use with a 10x1.0mm helicoil. So after completely drilling out the threads, I was able to remove what was left of the glow plug. With the tip still attached! So that's the good news.

The bad news is that at some point during my drilling adventures, I put a bad angle on the hole. See the crappy illustration below.

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So it was close enough for me to remove what was left of the glow plug, but not close enough for me to insert a new one with a helicol. It gets bound up, and I'm sure if I were to get it tapped with a helicoil and somehow managed to get the plug back in, that the glow plug shoulder would not seal properly with the head.

Luckily, I guess if anything here could be considered luck, I didn't mangle the entire hole. The 1/4 - 3/8 of an inch that's below the glow plug threads is still intact.

Oh and with no worries about having a glow plug tip rattling around in the combustion chamber, I went ahead and compression tested the other cylinders. Got between 400 and 450 on all of them, so I got that going for me.

Anyway, unless anyone has a better idea, here is my plan to fix this awful mess and hopefully still have a functional glow plug in cylinder 6.

1. Use a Dremel or similar to eat away at the top of the hole just enough so one of the old glow plugs will fit in.

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2. Insert an old glow plug so it sits in the part I haven't screwed with.
3. Take a diamond or carbide hole saw that just fits around the glow plug and use it to widen the hole with the glow plug as a guide. I have a diamond one that is nominally 1/2. Should make a hole around 0.52 Hopefully this will make the new even larger hole square so the glow plug will seat and seal properly.

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4. Tap the new larger hole hopefully to 9/16-8. Or maybe 3/8 NPT if I wallow the hole out too much while going at it with the hole saw.
5. Thread in a bushing matching the outside diameter and thread pitch, already having the center drilled and taped to 10x1.0mm for the glow plug. I think I can use a 3/8x1/4 iron pipe reducer bushing for this with the hex head cut off, but I'm going tomorrow to see what I can dig up at the hardware store.
6. Compression test cylinder #6.
7. Hopefully the compression test will be okay and then I can reassemble with red thread lock or maybe JB Weld on the bushing and anti seize on the plug, and be done.

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I guess if that doesn't work, I'll be tapping and screwing in a length of threaded rod with plenty of thread sealant or JB Weld, and saying goodbye to #6 glow plug. Then I'll probably go have a long cry, or a lot of whiskey. Hell probably both! Before I do anything else with this truck. Longest "15 minute" job I've ever done.

 

[Nero]

All I can say is...

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[Booyah45828]

https://www.amazon.com/Cylinder-Metric-Thread-Repair-33pcs/dp/B01MSZXB01

I believe the IDI uses 10mm glow plugs. This kit has timesert like thread sleeves, which are much better and more durable then a heli-coil. We have this kit in spark plug form for the ford modular 2v engines, and it works well. My problem with a helicoil is that there's a good chance it won't seal the combustion afterwards.

Your local auto machine shop might have one of these you could borrow if you sweet talk them.

 

[Rdnck84_03]

Longest "15 minute" job I've ever done.

Believe me I know the feeling! Project I just finally finished last weekend was planned to be about a 2 hour new Radiator install, flush the block and fill. Took almost 4 weekends and about 10 30 mile round trips to the parts store.

 

[Rdnck84_03]

I think you may have a solid plan there. My only concern would be are there any passage ways close around the glow plug hole that could be drilled into?

 

[bumblebeer]

Alright it worked!

I did pretty much what I outlined above, except the diamond hole saw chowdered out after only making it a 1/4" or so. But that gave me a good enough guide to line up a normal drill bit and drill it out the rest of the way.

Then I used a 3/8 to 1/8 reducer bushing. Tapped the center out to 10x1.0mm and modified a 3/8 NPT tap so I could bottom tap the GP hole in the head. Cut off the flats in the bushing and added some spots so I could thread it in. Put it in with some red loctite, and did a compression test. Got 415 psi! Installed the glow plug with some antiseize and now it's running good.

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[Rdnck84_03]

Hopefully it holds up as a permanent fix.

 

[Old Goat]

Iam impressed what you went through to get to the final results.
Most of us wouldn`t have thought of doing what you did.
You have to be a machinist run lath`s etc...

I don`t see why it won`t hold with the bushing threaded into the block, that should last longer than the truck. be sure to use Anti-Seiz on the GP Threads.

Goat

 

[Black dawg]

Good recovery

 

[Booyah45828]

Looks like a good fix so long as the plug's seat can still seal at the bottom.

Compression #'s look good, but fill the cavity with soapy water and then test it again, as any bubbles will show air bypassing and would be a true leak check.

 

[bumblebeer]

Thank y'all all for the support and advice! I did end up getting it running well, and did the soapy water trick as suggested and didn't notice any bubbles. So I think it's got a decent seal.

Unfortunately, I'm sidelining this truck for the moment. I've got another idi I've been working on here https://www.oilburners.net/threads/new-project-truck-think-ill-be-sticking-with-this-one.92418/ . I hope to get this old girl restored at some point especially since it's my first idi, but I'm afraid she may have to retire to being a parts truck.

 

[Jesus Freak]

Genius! Absolutely genius!

 

[Lumberjackchuck]

I’d say pull the motor so you can work like a gentleman.

And if you do pull it out it’s probably due for a reseal at a minimum.

I personally don’t like fixing something different every week, so if you got the time and some money it’s prob worth going thru everything