Helicoils in Aluminium heads 5

[Bentbeetle]

I have stripped the thread in a 1969 VW Beetle spark plug socket and can get from my local car parts store some 14mm aliminium coils (similar to "Helicoils"). I'm a little suspicious, though, as they seem to be fairly low grade aluminium. If they in turn strip out, then the head becomes useless. I have read that installing Stainless steel is a better option, though the dissimilar metals may release under high temperature... Am I being too fussy? Would the Aluminium ones do? The advice on the packet is to "Locktite" them in. Would that hold up umder load?

 

[waross]

I have had a lot of good luck with stainless heli-coils in outboard motors. I had 5 or 6, 20 HP 2 cylinder out boards.
The aluminum heads stripped out vewry easily, and I never had another problem once I put in stainless heli-coils. If one plug hole went, I usually put heli-coils in both while I had the tools out.
I don't understand where the helicoils could release to.
I think that aluminum, to a stainless helicoil, to a steel spark plug is a much better combination than aluminum to the steel spark plug. That combination has failed many times, hence the development of heli-coils.
yours

 

[SMOKEY44211]

I've had better sucess with the sleeve style that has external threads and a shoulder at the top. I believe they are made of stainlees steel. My original kit made or maketed by K-D tools had a tap and a few extra sleeves. I haven't been able to find anyone locally that carries that line anymore but I have been able to get replacement sleeves through NAPA. I suspect they also offer the tap needed. I have seen some other styles that you have to swedge the top over after you install it. Its a real pain if you happen to thread it in a little too deep, as it's almost impossible to back it out. The shoulder style is idiot proof.-----Phil P.S. run the engine for a few seconds with the plug out after you tap the threads to blow out the chips.

 

[Bentbeetle]

Wow! I've never subscribed to anything like this.... Results! Down here in NZ your brand names don't mean anything to me, but I'll ask the local supplies to track some stainless steel ones, I think I'd be happier. I'm a little intrigued by your post-script about blowing the chips out- I was preparing to pull the head off. Are you serious? If you think it's safe, I'd rather leave things alone- the compression in all cylinders is all over 145psi.

 

[patprimmer]

The method suggested by Smokey is far better.

I hot rodded air cooled VWs for years, and repaired more than one damaged thread.

Because the VW plug is a short thread, the helicoil must be the full length of the thread. It is then subject a small piece of the thread in the head failing and a small piece of the helicoil unspringing from head and changing the thread pitch for that portion.

The sleeve insert is solid and cannot "spring out" in this
fashion.

If you cannot buy them, a good machinist should be able to make them.

I would expect a good place to start looking for them would be H&M Ferman in Peakhurst in Sydney Australia.

I can get a phone number if you need it.


Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[BCjohnny]

"Wurth", Germany, I believe make the solid flanged type.

A liitle closer to home, "Re-coil" in Aus do re-threading kits, including 14mm spark plug sets, but they might only be the wire wound type.

Use the solid ones, and measure so they don't overhang into the chamber.

John.

 

[WilliamH]

The web site following is one type of thread repair we use with 100% success:

http://www.timesert.com

 

[bub579]

Please make sure the piston is down in the cylinder. Some of the taps mentioned above have an integral reamer to provide sizing and alignment. Grease the tap, leave the engine in and head on. Use the insert. Have fun, wunderbar

 

[Fabrico]

I wouldn't worry too much about reliability. Way back when, anyone who built VW's replaced the S/P threads automatically, even on brand new heads. Any good hardware or autoparts store used to sell inserts for them.

 

[Rob45]

You might find that this changes the heat range of the sparkplug somewhat, since you're putting a bit of an insulator in the path by which the sparkplug cools itself.

Run the engine hard once after installing the insert, see if there are significant differences between the modified and non-modified cylinders. It's conceivable you'd need to go one heat range colder in the re-threaded cylinder.

 

[patprimmer]

When I ran high compression VWs, whenever I had to put in one insert, I put in 4 for precisely the reason that the insert and plug ran hotter and affected plug readings and detonation.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Strider17]

I have done many VW heads with helicoils with much success.
They are much better than the solid inserts. Use white
grease on the tap, it will catch the chips and you don't
have to pull the head or engine.

The more you know, the more you
know you don't know....