How to Install a Helicoil That Won’t Retract

No matter the application, if you’re dealing with an assembly that has seen its share of wear and tear, you may come across a stripped thread. When that happens, you should install a helicoil to create a new thread for a fastener to grip.

Here’s how it works:

While it’s a great fix, when it comes time to remove the fastener, helicoils that have been in use for a long period of time can retract.

The blogger’s 1949 Ford F-1’s 239 flathead V-8 engine.

It’s a frustrating problem, but one you can avoid. When it came time to repair the header bolts on a 1949 Ford F-1’s 239 flathead V-8 engine, a fix was needed that would prevent the helicoils from backing out.

The Solution

1. Drill the stripped hole per manufacturer’s recommendation

To start, you’ll need to drill the hole based on instructions provided to you by the manufacturer to ensure a proper fit. The suggested drill bit size will depend on the size of the thread needed, as well as the parent material. Be sure not to drill any deeper than the hole’s original depth. Once the drilling is complete, you’ll also want to rid the hole of any debris by blowing it out with compressed air.

2. Tap the drilled hole with the tap specified in the helicoil kit

Tapping is what cuts new threads into your hole. Be sure the tap is perfectly straight, so your threads align properly. Gently turn the tap until you start feeling resistance. Once you do, slowly back the tap out and again blow out the hole with compressed air to get rid of any debris.

3. Apply LOCTITE^® 2620™ Threadlocker into the helicoil

You might be familiar with LOCTITE^® 2620™ as a red, high-strength threadlocker. In this case, the job involved attaching the helicoil to the insert tool provided and then applying LOCTITE^® 2620™ to the outside of the helicoil. 2620™ was selected because it is a high-strength threadlocker that can handle the high temperatures the headers will face. Depending on your application, you might choose another threadlocker.

4. Insert the helicoil into your freshly tapped hole

With red threadlocker applied, you can now insert the helicoil into your freshly tapped hole. The cure time for LOCTITE^® 2620™ depends on the temperature at the time of application, but we recommend waiting 24 hours to ensure full strength.

And that’s it! A helicoil installed with LOCTITE^® 2620™
 won’t ever retract if you need to remove the fastener.

Can You Use LOCTITE^® 262™ Threadlocker?

In short, the answer is yes. LOCTITE^® 262™ is a high-strength threadlocker just like LOCTITE^® 2620™, but can withstand up to 360°F rather than the 650°F that LOCTITE^® 2620™ can withstand. LOCTITE^® 2620™ was chosen for that reason, and because it tolerates surface contaminants from lubrication, anti-corrosion and protection fluids well. If using LOCTITE^® 262™, just apply it into the fresh-cut threads prior to inserting the coil; insert the coil; and let it cure.

Can You Use LOCTITE^® PC 3967™ Stripped Thread Repair Kit Instead?

In some cases, LOCTITE^® PC 3967™ Stripped Thread Repair Kit (Known as LOCTITE^® Form-A-Thread^®) has been used as an alternative to helicoils. This stripped thread repair method restores worn, stripped or damaged threads without drills, tools or inserts.

It’s a five-minute job, with a finished assembly that allows up to 128 ft. lbs. of torque within a wide temperature range. However, an application assessment should be performed to determine suitability, and keep in mind that even in those instances when PC 3967™ would be effective, helicoil repairs are always stronger.