RussB

When I removed the spark plugs in my newly acquired 88 5000CSTQ, they creaked and required much more torque than I've ever used to remove plugs . . . but they did come out, with the help of PB Blaster. My guess is that the plugs had been in the head for at least 5 years / 50,000 miles.

Now I fear that one hole may be leaking. Q: Has anyone here heli-coiled a spark plug hole? How did you keep the aluminum shavings out of the combustion chamber? What were the results?

TIA

rick5ktq

Rotate the crank until the piston in that cylinder is at it's top position on the exhaust stroke.
Do a real nice job on your heli-coil :-)
Get a really good vacuum cleaner and reduce the suction to the diameter of the spark hole.
Then suck anything out.

<b>Would I do this? No. I'd remove the head.</b>

Tom Faust

Since it is essentially a tap, most of the shavings will come out the top, not fall in. Keep it soaked with oil/grease while you cut, that will trap loose pieces. If it does fall in, it is only aluminum. The intake has no suction so it won't be trapped under a cold valve. I've done it.

Tom Faust

Of course, you could just put a copper gasket at the base of the plug.

dwengi

Personally I would remove the head. The heli-coil requires that you drill first and then tap.
Old trick to keep shavings from falling in is use grease on the drill and the tap.

rooster 2

it is amazing stuff. Just smear a little, and I mean a very little, where you want threads. Once smeared, screw in a spark plug with its threads coated with a release agent like vaseline. Give the JB Weld 24 hours to dry, then remove the spark plug, wipe off the vaseline from the threads, then retighten sparkplug back into the head. Don't super torque it down, but tightly snug it down. The newly created JB Weld threads should hold for a long time.

If you are dissatisfyed, then go the helicoil approach.

RussB

First I'll see if the threads will hold as is. The blow-by problem is intermittent. Just when I'm convinced that it's time to repair, the problem disappears (for a while).

As usual, the AW 5000 crew came through with valuable BTDT.

5kcstq

I popped my hood once to find the plug bouncing around in the no-longer-threaded hole for the #5 plug. The Time-Sert design is a sleeve with a shoulder at the top and is swaged(?) (expanded) at the bottom when installed, resulting in tight fit.

While Helicoils are available for that application, I prefer to use those only for blind holes. I can conceive a situation where a Heli-Coil would screw itself into the head or otherwise not be centered in the threaded hole over time. They are held in place by tension when empty, as I understand it.

I put grease on the tap to catch most or all of the metal chips. No problems with the repair, outside of the stress of discovering missing plug threads!