Spark Plug Thread Repair Kit Suggestions?

[woodstover]

When we had our VW aircooled shop we used tons of helicoils for spark plugs/exhaust studs. Always a success. Used red loctite when installing. As a shop, we would buy starter kits for what was required and then just ordered extra inserts kits as required. Slowly built up to having all the common thread sizes. A few seldom used sizes we would buy a longer insert refills and just cut them to length instead of buying different lenghth refill kits.

 

[StarTech]

That is the problem that cheap kit is not a Heli-coil version but is a threaded insert. Plus they are reaming the hole and then tapping it for the insert all in one operation. Next time I try the kit I brought I am going just drill the hole and they tapping it. But I am looking for regular Heli-coil tool sets for the 10, 12, and 14mm plugs. I know three different kits so that is around $400 to start with.

 

[Rivets]

Have you seen this kit, had one in the last shop I worked in, before i retired. For M14 I used spark plug tool. https://www.vevor.com/home-tool-kit...MIpbm_3Y_6kAMV7lR_AB0u8Ra5EAQYCSABEgKZavD_BwE

 

[StarTech]

Not even the right thread pitch.

I need M10-1.00, M12-1.25 and M14-1.25.

 

[sgkent]

thread cert is more common in the air cooled world. The best fix is to make a video on replacing the head, or show someone how to properly remove the head, weld it, surface, and drill / tap a new plug hole. I would only use a heli-coil or thread cert on a head that was NLA used or new, or very expensive. Lots of the old mower engines from the 1990's are out there in masse as to used parts. Both thread certs and heli-coils can fail or be problematic when the plugs comes the next time the it is removed. So ask yourself why go thru all the hoops to remove and then repair it, then put the old one back when you could have a replacement ready to go.

 

[Rivets]

What about these individual kits?

E-Z Lok E-Z Coil Thread Repair Kit for Metal - Standard - M10-1.0 x 3/8 SK50932 | Zoro

Order E-Z Lok E-Z Coil Thread Repair Kit for Metal - Standard - M10-1.0 x 3/8, SK50932 at Zoro.com. Great prices & free shipping on orders over $50 when you sign in or sign up for an account.

www.zoro.com

E-Z Lok E-Z Coil Thread Repair Kit for Metal - Economy - M12-1.25 x .500 EK51034 | Zoro

Order E-Z Lok E-Z Coil Thread Repair Kit for Metal - Economy - M12-1.25 x .500, EK51034 at Zoro.com. Great prices & free shipping on orders over $50 when you sign in or sign up for an account.

www.zoro.com

E-Z Lok E-Z Coil Thread Repair Kit for Metal - Standard - M14-1.25 x 3/8 SK51132 | Zoro

Order E-Z Lok E-Z Coil Thread Repair Kit for Metal - Standard - M14-1.25 x 3/8, SK51132 at Zoro.com. Great prices & free shipping on orders over $50 when you sign in or sign up for an account.

www.zoro.com

 

[Tiger Small Engine]

thread cert is more common in the air cooled world. The best fix is to make a video on replacing the head, or show someone how to properly remove the head, weld it, surface, and drill / tap a new plug hole. I would only use a heli-coil or thread cert on a head that was NLA used or new, or very expensive. Lots of the old mower engines from the 1990's are out there in masse as to used parts. Both thread certs and heli-coils can fail or be problematic when the plugs comes the next time the it is removed. So ask yourself why go thru all the hoops to remove and then repair it, then put the old one back when you could have a replacement ready to go.

Helicoils are normally very reliable long term if installed correctly. Who would go to the trouble of removing the cylinder head, welding it, tapping a new hole, probably have to replace head gasket, and reinstalling cylinder head? That sounds like something they would do in Pakistan.

 

[StarTech]

At 3/8" that is only 9.5mm reach and I need something closer to 12.7mm reach on the 10mm plugs and both the 12mm and 14mm are way too short at 12.7mm (12mm) and 9.5mm (14mm). Both the 12mm and 14mm plugs I use here have a 19mm thread reach.

I found what I was looking for. By sure accident McMasters vendor sent me the wrong tap for a current project. Just a mix up on packaging but this time it is beneficial to me. There was enough info on the tap to lead me to a master Helicoil chart with kits, individual sets of Helicoils, and all the various installation tools. It even gave me the drill bit size for each. Even at $79 for a full installation tool kit is a heck a lot better than the one at McMasters for $354.

I believe the problem with the current kit on hand is simply that the holes needs to be pre-drilled instead of the tapping tool doing it. I should know later today provided don't start raining. My neighbor may have the bit I need. If I still come up with a loose fit then I only those inserts on tapered plugs. I rarely see tapered plugs here.

Either way I need a tax write-off so I be getting the regular Heli-coil kits. I can always trim the 1.5D coils to 1.25D size for the 10mm and 14mm and the 1.5D coils are fine for the 12mm plugs. That would give me 12.5 , 18, and 17.5mm coils for the 10, 12, and 14mm plugs respectively. Now the shorter 14mm plugs used in the old L heads (ie RJ19LM for example) does have a 9.5mm reach so that kit listed above would work fine as they are .68D coils.

 

[sgkent]

Helicoils are normally very reliable long term if installed correctly. Who would go to the trouble of removing the cylinder head, welding it, tapping a new hole, probably have to replace head gasket, and reinstalling cylinder head? That sounds like something they would do in Pakistan.

Huh? I was machinist in a well known high end racing and fleet machine shop once. I can't imagine any reputable mechanic letting drill and tap filings fall down into the cylinder to get caught in the cylinder and whiz around, or wedge the valves open a bit. THAT sounds like something from the third world or Bob's DIY Old Oak Tree Garage. I am out of this forum if that is the preferred method of repair. Frankly, I'd just get a good used head off Ebay from a seller with a 100% rating and 5,000 items, check it for warp and replace the head. Most heads are fairly easy to remove because small engines usually say in the manual to decarbonize them every so often.

 

[Auto Doc's]

Hi sgkent,

Don't take it personally.

Many who visit this site are only looking for the immediate "fix" to their dilemma, not a correct or permanent one.

Some of the suggestions make me laugh, but I don't take them personal.