I just had up a post about an ejected spark plug (90 740turbo with 282K miles)

I checked again and the threads are gone, except for about two turns at the very bottom.

Does anyone have special advice about using a heli/t-coil insert? I've never done it before, and doing it into an aluminum head as my first time is a little daunting.

Also, how do I know what size tap to get? Do I need to take in a matching spark plug?



Thanks,
Will
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1990 740 Turbo, on its way to stock specs, maybe beyond

I tapped new threads last night, using the grease, tap, remove, re-grease, and installed the insert tonight. I went with a napa kit, the tool for time-serts was on loan for two weeks, and it's a bit overkill.

I checked as well as I could for flakes and pieces. I swabbed the cylinder with q-tips dipped in the heavy grease I used to lube the tap.
I removed one chip from the top of the piston, but didn't find any others.


I installed the spark plug after the thread-locker and silicone set (3 hours later) and started it and ran it until warm.

I didn't hear any abnormal noises, no scraping, but maybe a very very slight metal on metal noise (could have been normal noise I usually miss). Almost sounded like a normal belt accessory noise.

Engine seems to run fine but I didn't drive it anywhere.....

Can I stop worrying now??

-Will
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1990 740 Turbo, on its way to stock specs, maybe beyond

Do I need to be concerned about the heavy grease getting into the cylinder head?

The type I have on hand is Multi-Purpose Lithium Grease. It says dropping point 350F and NLGI #1-1/2

I don't think much will get into the cylinder, but just in case.

Thanks,
Will
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1990 740 Turbo, on its way to stock specs, maybe beyond

Just google "helicoil installation" and you'll find all you need to know. The kit includes the special drill and tap. Of course it would be much easier to do it with the head off, but I suppose it's possible to do it in situ if you're clever and careful. #1 cylinder would be easiest, getting more difficult to maybe impossible as you go farther back.

Did a little research, and I'm looking at getting time-coils. They're solid pieces, not coiled wire.
I'll probably add permanent thread locker behind the time-coil (can't do that with standard coils).

Looks like I need the extended kit.

Still looking for any advice,
Happy Bricking,
Will
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1990 740 Turbo, on its way to stock specs, maybe beyond

I never did one. I thought these kits give you a tap and the required drill size. I would run a vacuum cleaner as I drill and tap to keep some of the chips out of the Cylinder.
Future Spark Plug install:
I always use a short piece of 3/8 gas hose to insert my Spark plugs. Push the hose onto the plug, it helps give you the extra length you need to get in the Head and yet it offers the sensitivity so you don't cross thread that you can't get with an extension on a socket
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'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me http://home.no.net/ebrox/Tony's%20cars.htm

Thanks for the replies

That's a great idea for installing the plugs!

It looks like it's going to be manageable. I'll post back if I blow up my engine :O

Happy Bricking,
Will
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1990 740 Turbo, on its way to stock specs, maybe beyond

I don't want to shell out $150+ for a special tool. Why not just use a standard tap tool and buy a t-coil for $2..... ?

-Will
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1990 740 Turbo, on its way to stock specs, maybe beyond

You HAVE to use the special tap because a larger tap will have a coarser thread.
You have to have exactly the same pitch as the spark plug and original threads.
You also have to have the exact right diameter so that the insert seats properly and leaves the
inside diameter of the threads exactly what you want.
That is why they furnish the special tap and also why it is expensive - If they don't sell it for their application
it can't be used for anything else!
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George Downs, Bartlesville, Heart of the USA!

I've done more than one of these...but not on a volvo. Helicoil makes a kit to do it. It's called Sav-a-thread. It has solid inserts like a time sert. Advance auto had them but you can also buy them online. It comes with a tap that is "supposed" to bite into the existing (remaining) threads. The tap has a set of cutters and a larger tap (for the new threads). The theory is just put it in let it cut it's way until it bottoms out. This did not work for me so I had to buy a drill bit, drill out the plug hole, and use the tap to create the new threads for the insert. Once the new threads are in, you screw in the insert and lock it in with an expander tool that comes in the kit. Not very difficult but it feels really weird to drill the cylinder head!

Some tips if you choose this method;
1 Make sure the piston is all the way down or else you'll drill a hole in it or damage it with the tap! If you drill make sure you are as straight as possible, using the angle of the other spark plugs as a guide. If it's #3 or 4 this may be impossible.

2 Coat the drill bit and/or tap with wheel bearning grease. This makes it cut easier and will hold most of the metal fragments.

3 Be patient. Turn the tap no more than 1/4 to 1/2 a turn at a time then back it out. Nibble away at it until you are all the way through.

4 As you are backing the tap in and out, remove it every now and then, clean it with brake cleaner to remove the grease and debris, then recoat with grease and go again. This will ensure you pick up most of the metal.

5 Before putting in the insert, rotate the piston back up. As it comes up use a flashlight to look for any shavings on top of the piston. Use a long q-tip with a small dab of grease to mop them up. This is alot harder than it sounds as there is not enough room for the light and the q-tip. You have to guess, take a stab at mopping and then look again.

I don't think I paid more than $30 for the kit. Use anti-seize on all your plugs. A tiny bit goes a long way and prevents this from happening again.

HEY! Thanks for the help. That's the best post I've read, and has the best insider tips.

The Q-tip is a great idea, and I had no real, good idea for dealing with the shavings.

What's the best way to rotate the piston? Torque wrench on the crank bolt?

and THIS:
"
1 Make sure the piston is all the way down or else you'll drill a hole in it or damage it with the tap! If you drill make sure you are as straight as possible, using the angle of the other spark plugs as a guide. If it's #3 or 4 this may be impossible."

Is critical and nobody had told me anything about it. Thanks!

I've already got the time-sert in the mail, I think it's a way superior design and isn't going to cost me any more than the $50 kit at Napa.

I like the top lip, so it can't be installed too deep, and I like the bottom side locking feature. I suppose the top would be okay, but it seems more secure to have it sandwich the head to hang onto it. I also plan to put permanent thread locker on the outer threads of the insert.

As for antiseize, I have used it ever since the first spark plug change I did.

Thanks very much,
Will
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1990 740 Turbo, on its way to stock specs, maybe beyond

Someone wiser than myself once advised to crank the piston down and to fill the cylinder with shaving cream. You then do the drilling and tap work and vacuum out the chips and foam with a shop vac when you are done. I have yet not tried this method personally but it seems pretty slick and in addition to mopping up chips with the q-tip you can be pretty sure to get most if not all of the chips out.

Mike

Haha, most excellent. I may try that. Did they say anything about contaminating your oil with shaving cream?

Also, how do you really get a shop vac into the hole? a crevive attachment? Apiece of vacuum tubing?
I'll probably just use my upright vacuum hehe...
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1990 740 Turbo, on its way to stock specs, maybe beyond

"What's the best way to rotate the piston? Torque wrench on the crank bolt?"

Yes, or a breaker bar. It doesn't have to be at bottom dead center, just outta the way.

The shop I once worked at did it by having the exhaust valve open, and when done blowing compressed air into the hole and sending most effluvia out the pipe. They did many this way and never a problem.
The grease on the tap and remove, clean and redo is most excellent also.