[RV6_flyer]

Any one ever have a helicoil come out when you removed a spark plug?

How did you fix it or how would you fix it?

 

[aerhed]

Yup. If the wholle thing came out & the threads in the head are good, you can just twist in a new one. If threads are slightly boogered a heli-coil tap may clean them good enough to put in a new coil. I've had them with just the tip bent out and trimmed them with a die grinder.

 

[chaskuss]

A tip

Yup. If the wholle thing came out & the threads in the head are good, you can just twist in a new one. If threads are slightly boogered a heli-coil tap may clean them good enough to put in a new coil. I've had them with just the tip bent out and trimmed them with a die grinder.

Gary,
Once you install a new insert, you have to break off the "tang" from the bottom of the HeliCoil insert. The sharp edge left after the tang is removed prevents the insert from moving downward into the cylinder. Obviously, it would ruin your day, if you drop the tang into the cylinder. [Not that someone like you would be so clumsy]
For mere mortals, I have a trick to prevent that from happening. Before installing the Helicoil insert, rotate the engine so that the cylinder in question has it's piston near TDC. Using a can of cheapo shaving cream [it's just soap] and a plastic tube, fill the area above the piston's crown with shaving cream.
Install your insert and break off the tang. If it falls, it simply lands on top of the shaving cream. You can then use either long, thin needle nosed pliers or a shop vacuum to remove the tang. Use the shop vacuum to remove most of the shaving cream from the cylinder. Don't worry about the excess. Soap won't hurt the innards of your engine.
FYI, if you have to run the tap in to clean up the threads prior to replacing the HeliCoil, put the shaving cream in first. It will catch any aluminum shavings that fall off the tap. Remove any metal debris and the shaving cream using the shop vacuum.
This trick works great any time you need to drill, tap or grind in an area where you would not want to leave grit or metal behind.
FYI, both 14mm and 18mm spark plug Helicoil inserts come in multiple lengths. Be sure to obtain the correct length of HeliCoil insert for the spark plugs you are using.
Charlie Kuss

 

[aerhed]

I like that shaving cream trick for drilling, etc. For the coil tang I'd just use needle vise grips or a stout hemostat. Of course, I'm a lazy risk-taker.

 

[pierre smith]

Thanks Charlie

Shaving cream!! Who'da thunk?

This site never ceases to amaze me.

Best,

 

[Bob Gordon]

What causes loose helicoils

Just thinking about why this happened to Gary. During my last compression test (O360-A1A, ECi cyls.) I noticed a sharp snap release of the plugs when breaking the torque. The plugs came out fine otherwise. The only thing different this time was I did not use spark plug thread lubricant the last time I put the plugs in - forgot the stuff back home. I installed them as always, with a torque wrench at 35 ft.lb. Normally the plug with thread lubricant just gives easier when untorqued, and does not produce that nasty-sounding snap like something just broke.

So I'm thinking, could such an instantaneous unloading cause the helicoil to loosen and start to rotate? BTW, I do not know if Gary uses or does not use thread lubricant.

 

[rocketbob]

I would borescope the cylinder just to be on the safe side. Cylinder cracks always go from one of the spark plug holes to the exhaust valve, and this could be a symptom of a crack.

 

[chaskuss]

Shaving Cream

I like that shaving cream trick for drilling, etc. For the coil tang I'd just use needle vise grips or a stout hemostat. Of course, I'm a lazy risk-taker.

Dave,
You're not a "lazy, risk-taker". You are skilled and confident! I came up with this idea about 30 years ago, when I owned a motorcycle repair shop. It allowed me to repair stripped out spark plug holes without having to remove the cylinder head. [People only bring a vehicle to a professional mechanic AFTER they've tried to fix it themselves and made it worse]
It's VERY handy if you need to repair a stripped bolt hole in a car's [DOHC] cylinder head. I will cover the entire head area, including the camshafts, before I start to drill and tap for the HeliCoil.
Did you ever notice that it's ALWAYS the final bolt that breaks or strips??? That Murphy guy is a real pain sometimes.

The thread lubricant, as Bob referred to it [aka anti-seize compound] definitely helps prevent the plug from removing the insert. I use anti-seize compound on most fasteners going into aluminum [on cars] A great area to use it on, is the joint between your alloy car rims and the brake rotor/wheel hub. Here in SE Florida, as in the northern States, alloy rims will seize, due to the salt corrosion. Try changing a tire by the side of the road [with minimal tools and a wobbly jack] when the rim is seized to the hub. I've had rims on customers cars/trucks which required the use of a 10 pound sledge hammer on the tire side wall to break them free.

Bob's suggestion of bore scoping the cylinder is a great idea.
Charlie

 

[Vern]

Signs along a dusty Texas Highway near the airport

Trash in the engine?

Access too tight?

Fill it with Burma Shave!

Do it just right!

BURMA SHAVE !

 

[AX-O]

All,
the reason Gary asked the question is because it happen to me, not him. I did use champion thread lubricant. The two times I have removed the plug on that cylinder, it has felt like the thread was cross threading. felt like it had a lot of friction on the way out. There is an A&P in the next town over that is coming today to see if he can fix it without removing parts. I plan on taking pictures and documenting the experience so it could be beneficial to others.

 

[aerhed]

Charlie, thanks that really is a neat trick.
Bob has good thought too (why loose).
Axel, it probably has been cross-started at some time, it happens. A careful start and clean-out with a plug thread cleaner (big tap) might do ya.

 

[rocketbob]

The best place for Champion "anti-seize" is your trash can. It is graphite-based and once the oil is gone, you have a nice dry coating of graphite that's gets hard and makes the plugs turn with difficulty. Use a good nickel-based anti-seize instead.

 

[artrose]

Spark plug cross threaded in a helicoil. Plug threads were boogered, as well as the helicoil. Remove the old helicoil, pull the other plug on the cylinder, disable the mags, tie the prop down, install the compression gauge fitting on the other plug hole, piston in compression, pressurize the cylinder with compressed air, chase the threads, (all the debris from the cutting die blows back up through the grooves in the die) kill the air, screw in the new helicoil, and use a good set of needle nose the pop the tang. Not difficult, and there's no cutting debris left in the cylinder.