• Welcome aboard HomebuiltAirplanes.com, your destination for connecting with a thriving community of more than 10,000 active members, all passionate about home-built aviation. Dive into our comprehensive repository of knowledge, exchange technical insights, arrange get-togethers, and trade aircrafts/parts with like-minded enthusiasts. Unearth a wide-ranging collection of general and kit plane aviation subjects, enriched with engaging imagery, in-depth technical manuals, and rare archives.

    For a nominal fee of $99.99/year or $12.99/month, you can immerse yourself in this dynamic community and unparalleled treasure-trove of aviation knowledge.

    Embark on your journey now!

    Click Here to Become a Premium Member and Experience Homebuilt Airplanes to the Fullest!

spark plug inserts?

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

splischke

Scott Plischke Sonerai IIL N994SP
Joined
Dec 28, 2005
Messages
1,743
Location
Amarillo, TX
Maybe this is one of those things everybody knows not to do except me...

I have the heads off the Sonerai for valve lapping. Since the heads are off, I decided to run a spark plug thread chaser tool to clean-up the threads. After I did the left head, I inserted the plugs and noticed that the chaser had enlarged the holes enough to allow the plugs to wiggle until they seat. The wiggle is more than enough to make me uneasy. Time for inserts...

I thought this will be like any other spark plug thread fix -- get a helicoil of the right size from the corner auto parts store and install. Then I hit the internet and found a whole bunch of opinions on spark plug inserts that my head is spinning.

Some people say not to use helicoils 'cause they can act as glow plugs to cause detonation.

Some people say to use Full-Torque inserts (http://www.fulltorque.com/sparkpluginserts.htm) since they are made of aluminum and expand at the same rate as the head.

Some people swear by Time-Sert inserts (http://www.timesert.com) since they offer the most permanent fix and include a new seat for the plug.

What do you guys think? What's best for our aero-VWs with their aluminum heads?

-Scott
 
Scott
I've tried many types of thread inserts on cars ,bikes and many small engines,including my ultralight aircraft and I will never use them again...except for helicoils...
Don't waste your time and money with anything else.
some of the other type inserts came off with the plug .
Helicoils won't do any glow plug effect if you cut the excess length with a dremmel...
I have had 8 of these helicoils on my actual heads installed (by a head machine shop) as a preventive measure,to avoid in field problems with spark plugs...
and I'm glad I did...
I also used them for years on my 1835

Gaston
 
8 hours on my HeliCoils now, but I have not removed the plugs yet. Timeserts seem to have a good reputation, but I have 0 experience with them.

I was very careful to not let any of the HeliCoil hang into the chamber for fear of detonation. I used a small file to make them flush with the chamber.
 
Thanks Gaston and Jeff. More comments from others are welcomed.

Gaston, of all the inserts that you've used, have you tried Time-Serts?

In my "research", I can't find a single complaint about Time-Serts. But Time-Serts have not been around as long as Heli-Coils and are used less often so I expect less complaints.

The Time-Sert inserts themselves are cheap -- on par with Heli-Coils -- but the installation tools are not. The best price I found for the 14mm tool set is $145. Gaston's comment "Don't waste your time and money with anything else" is echoing in my head.

As for the glow-plug effect with Heli-Coils, I think this is due to improper installation since I found only one reference to this issue. A more common problem I've read with Heli-Coils is that they sometimes come out with the plug. One guy advocates using blue lock-tite during installation. I don't know about this considering the 300+ temperatures at the plug.

My research included a trip to YouTube where I found this video:

http://www.youtube.com/watch?v=LCtXiwlQsiU

-Scott
 
don't know time-serts

this is new to me but I've tried something very similar,a long time ago...
as long as Helicoils will be available,I won't try something else...

a long time ago in my early days of ultralight aviation,I remember using some kind of inserts trying to save a head... and finally installed a new head.

correctly installed helicoils are the way to go...highly cost effective
I've removed and installed plugs more often than usual this summer without concern on this...
I wouldn't dare to install anything else as a preventive measure...

this is surely a biased opinion ,but in my mind ,it's biased on the right side...
Ha Ha Ha

Gaston
 
Scott,

There is a high Temp formula of Loctite that I have used at work. I believe it was good up to 650F (?), I know we had to heat it with a torch to break it loose.
 
Bruce333 said:
Scott,

There is a high Temp formula of Loctite that I have used at work. I believe it was good up to 650F (?), I know we had to heat it with a torch to break it loose.

Do yo have a P/N and source? I visited the Loctite site and didn't see a high temperature variant. The Blue formula is what was recommended but Loctite says its good only to 300F.

I wonder how many Heli-Coil failures where the insert unscrews is due to Loctite seeping through the insert's coil and bonding to the plug - ? Perhaps it is best not to use Loctite at all. Dunno.

Another issue I've read about Heli-Coils is the coil winding into the combustion chamber during plug installation/re-installation. This is mentioned on the FAQ http://www.timesert.com/html/faq.html#1

Gaston, you have me just about sold on Heli-Coils.

-Scott
 
After spending much time researching the subject and weighing the pros and cons on the various methods of repairing a stripped spark plug hole, I decided on Time-Sert inserts.

I could not find a single bad comment about Time-Sert inserts. I called 5 different local machine shops and all use Time-Serts exclusively and since they started using them, they have not had a single reported failure.

I decided to let a local shop install two 14mm Time-Sert inserts on the top spark plug holes that my chaser tool had enlarged. It cost me $25 each.

I was so impressed with the Time-Sert inserts that I decided to tend to a 10mm secondary ignition spark plug hole that had minor thread damage. But for this one, I decided to do it myself so I ordered a Time-Sert installation kit from a fine gentleman and eBay Power Seller. His web site is http://www.toolsqwik.com.

The Time-Sert insert was easy and fast to install and the tools make it almost fool-proof to botch the job. The Time-Serts inserts are thinner than Heli-Coils so they require less removal of head material. In fact, no drilling is required -- just tap the original hole with the special tap and install the insert. The tool even cuts a new, perfect looking seating surface for the plug's washer. I now have a pristine 10mm spark plug hole with an insert that is impossible to wind in and almost impossible to unscrew.

I have 3 hours on the engine since the inserts were installed and the engine runs like a champ.

http://www.youtube.com/watch?v=Ntiy8L97Nco&feature=player_embedded

-Scott
 
When we used to drg race bugs we would put the helicoils in from the inside out. then dress the plug seat up. they couldnt blow or twist out.
 
Scott
Do you remember what size 10mm insert you used? I just removed two plugs and had three threads come out with each plug. They were so tight going in I feared this would happen. Thanks for the info on the Time-serts. They are new to me.

Mark Garrett
 
Well, during my annual on 685L I managed to strip a 'top' spark plug thread - and with the correct torque and anti seize applied at the last annual! Reading this old thread of Scott's I think I've found the solution. The kits have gone up in price since 2012 and now sold on Amazon. This looks like the correct kit for the top plugs but I would appreciate confirmation before spending $240. Also, has anyone actually completed the repair using the kit?
Time-Sert M14x1.25 Spark Plug Thread Repair kit p/n 4412E-111
Matt
 
$240 is a lot of bread for an insert. The kit consists of a helicoil tap, insert, & tool to install the insert.
Before I went that way, I'd search through the Helicoil site. They pioneered this technology in 1938. see https://www.helicoil.in/
One of the issues is that after tapping and installing you need to get out the 'filings' and the little tang from the insert which will break off inside the cylinder. Possibly a piece of plastic tubing taped to your shop vac might do the job. Ensure the piston is at TDC before tapping.
Bill E

Well, during my annual on 685L I managed to strip a 'top' spark plug thread - and with the correct torque and anti seize applied at the last annual! Reading this old thread of Scott's I think I've found the solution. The kits have gone up in price since 2012 and now sold on Amazon. This looks like the correct kit for the top plugs but I would appreciate confirmation before spending $240. Also, has anyone actually completed the repair using the kit?
Time-Sert M14x1.25 Spark Plug Thread Repair kit p/n 4412E-111
Matt
Well, during my annual on 685L I managed to strip a 'top' spark plug thread - and with the correct torque and anti seize applied at the last annual! Reading this old thread of Scott's I think I've found the solution. The kits have gone up in price since 2012 and now sold on Amazon. This looks like the correct kit for the top plugs but I would appreciate confirmation before spending $240. Also, has anyone actually completed the repair using the kit?
Time-Sert M14x1.25 Spark Plug Thread Repair kit p/n 4412E-111
Matt
 
https://vwparts.aircooled.net/Time-Sert-Tool-Rental-14-x-1-25mm-4412-p/time-sert-rental-4412.htm
I installed copper time-sert inserts in all of my 14 mm plug holes. I purchased the inserts and rented the tools from the aircooled.net guys. It's a pretty easy process. You have to visually inspect to make sure the hole is appropriately "faced" for spark plug washer to seat correctly. The photos in the video linked earlier in this thread show proper and improper finish.

Todd
 
Glad I asked - I didn't know of the rental option! Thanks both!!

To clean out the cylinder afterwards did you use the Shop-Vac suggestion? Bill, I was thinking the same.
 
Back
Top