Best Spark Plug Thread Repair Kits

A Quick Guide for Choosing the Best Spark Plug Thread Repair Kits for your Vehicle!

When the reality sets in that the threads on one or more spark plug sockets on your vehicle’s engine is damaged it can be pretty upsetting.  This condition can cause a host of issues with engine performance spark plug socket threads damaged by corrosion including misfiring, rough idle, slow acceleration, difficulty starting, and more.  Fortunately, the threads can be restored in most instances to as-new condition by using a spark plug thread repair kit.

Consequently, not all spark plug thread repair kits are appropriate for use in all vehicles.  Auto manufactures have never standardized spark plug socket thread sizes so its important that you select the appropriate kit that’s best suited for your vehicle’s engine.

Performing a successful repair job can be a challenging process depending on they type of vehicle you own. However, with patients and some basic mechanical skills the determined do-it-yourselfer can perform a successful professional quality repair.

How Do Spark Plug Threads Become Damaged?

Its helpful to understand how spark plug threads become damaged to prevent future occurrences. There are basically four ways a spark plug socket thread can become damaged:

#1  Cross-Threading – The most common way spark plug socket threads become damaged is cross-threading. Even for experienced mechanics cross-threading is very easy to do because of having to work in cramped engine compartments. Cross-threading makes it difficult or impossible to screw the plug all the way until seated. When cross-threading occurs the threads should be repaired for optimum engine performance.

#2  Over Torqueing – The second most common cause of damaged spark plug threads is over torqueing.  When too much torque is applied to a spark plug it can strip out the internal threads.  Thread stripping is most common with Aluminum engine blocks but can also happen with cast iron.  This condition must be addressed to restore engine performance.

#3  Corrosion – If water finds its way into spark plug threads it can rust the threads and in severe instances the threads must be replaced.

#4  Blow-Out – If a spark plug is not properly seated or over tightened blowout can occur destroying the socket threads.

No matter what the cause of your damaged spark plug socket threads they must be repaired for your engine to operate efficiently. Choosing the right Spark Plug Thread Repair Kit is the first step.

What is the Best Spark Plug Thread Repair Kit for My Vehicle?

There are spark plug thread repair kits available for just about any popular vehicle, new or old.  Some kits are generic and designed to address damaged threads in a wide range of vehicles.  Generic kits are usually for either domestic vehicles or for imported vehicles that have the same spark plug thread size and seat. There are also model-specific repair kits available for certain vehicles that require highly specialized tools to be able to do the job correctly.properly repaird spark plug socket threads and seat

To choose the right kit for your vehicle its helpful to know the spark plug thread size.  Also, its imperative that you choose a kit that has the proper seating tool for your vehicle’s engine.

Just as important as it is to repair the damaged thread with the correct thread size, the spark plug seat must be re-cut in order for the plug to properly seal once it is installed.  There are two types of spark plug seats:  Tapered and Washer Seat.

The best kits will include a seating tool that will re-cut the metal where the spark plug shoulder bottoms out on the head.  These seating tools are designed to re-cut or the seat so the seat so it is exactly 90 degrees (perpendicular) to the axis of the spark plug thread.

#1    Spark Plug Thread Repair Kit – RECOMMENDATIONS

I have researched the many kits that are currently available to make sure I only recommend the ones that are the best.   I narrowed down my list to the TIME-SERT Brand because of the quality and design of the tools, plus the completeness of the sets.  These are not the cheapest sets but if used correctly they enable you to do a professional repair job.

I would encourage you not to go the cheap route because you may only have one opportunity to do this repair job correctly.

To make selecting the right kit as easy as possible I have listed both the Models and Thread Size with each recommendation.

Time-Sert M14x1.25 IMPORT Spark Plug Thread Repair kit p/n 4412E-111


Time-Sert M14x1.25 IMPORT Spark Plug Thread Repair kit 4412E-111

  • Vehicle Model/s:  Acura, Honda, Lexus, Toyota, BMW, Mercedes-benz, VW, Audi, Mini Cooper, Kia, Volvo, and others
  • Thread Size:  M14x1.25
  • No. of Inserts: 5
  • Tools:  Long Reach Drive Wrench, M14x1.25 Step-Tap, Insert Driver, and Seat Cutter


If your import has a damaged spark plug socket, chances are you can repair it to as-new condition yourself with the Time-Sert Spark Plug Thread Repair kit.

This kit is designed for professional use but can also be successfully used by any DIY (do-it-yourselfer) who has some basic mechanical skills. Each tool in this kit is made to exacting tolerances and will enable you to reach plug sockets that are deep in the engine head.

The kit contains a Drive Wrench, M14x1.25 Step-Tap, Insert Driver, Seat Cutter, and 5 Inserts designed for washer-seating spark plugs.

No drill bit is needed to open up the original tapped hole. The Step-Tap is designed to pick up what’s left of the original threads to guide the larger M14 threads to cut new threads. Once the hole has been tapped to full depth the Seat Cutter is used to create a spot face that’s perfectly square to the tapped hole. This is critically important so the plug and washer will form a tight seal with the head.

To help you do a professional job there are detailed step-by-step INSTRUCTIONS that show you exactly what to do.

The Time-Sert M14x1.25 p/n 4412E-111 is the best spark plug thread repair kit for most import vehicles. It’s a bit pricy but only a fraction of what you would pay a pro mechanic at an import dealership or garage.

check price of Time-Sert M14x1.25 IMPORT Spark Plug Thread Repair kit p/n 4412E-111 at amazon


#2   TIME-SERT M14x1.25 DOMESTIC Spark Plug Thread Repair kit p/n 4412E-187


TIME-SERT M14x1.25 DOMESTIC Spark Plug Thread Repair kit p/n 4412E-187

  • Vehicle Model/s:Made in the USA Chrysler, General Motors, GMC, and others
  • Thread Size:M14x1.25
  • No. of Inserts:(2) each 24mm dia. X 15.7mm and 10mm reach
  • Tools:Driver Wrench, M14x1.25 Step Tap, Insert Driver, and Taper Seat Cutter


The TIME-SERT DOMESTIC Spark Plug Thread Repair kit is for restoring M14x1.25 plug sockets with TAPER SEATs found in many USA built vehicles.

Each tool is thoughtfully designed to do a professional job quickly and reliably. A Wrench with a T-Handle is used to drive each tool. The M14x1.25 Step Tap follows the original threads and at the same time cuts the new and larger thread to accept the included Insert. Once the hole is taped the Seat Cutter is used to cut a Tapered Seat so the spark plug will form a perfect seal when tightened.

TIME-SERT Spark Plug Repair Kits are the ones pro auto mechanics because they are top quality and are designed to restorer damaged spark plug threads to new condition. Keep in mind TIME-SERT inserts are for FIRST TIME REPAIR ONLY.

check price of TIME-SERT M14x1.25 DOMESTIC Spark Plug Thread Repair kit p/n 4412E-187 at amazon


#3   Time-Sert F0rd TRITON Spark Plug Repair Kit 5553-8 w/ 8 Inserts


Time-Sert F0RD Triton Spark Plug Repair Kit 5553-8 w/ 8 Inserts

  • Application : Restoration of Ford TRITON spark plug socket threads
  • Thread Size: M14x1.25
  • No. of Inserts: (8) Triton Inserts
  • Tools: Wrench, Long-Reach Reamer, Tap, Insert Driver, Setting tool, 1/8” and 3/16” Hex Keys, Triton, Counterbore, and Thread Sealer


If you happen to own a Ford vehicle with a TRITON V8 engine (like I do) with one or more damaged spark plug sockets the Time-Sert 5553-8 Spark Plug Repair Kit is the best option. This Kit contains every tool necessary to be able to restore those hard-to-reach plug sockets with good as new threads.

Included with the kit are a drive wrench, reamer, tap, insert drive tool, and a setting tool, counterbore, and sealer. Complete easy-to-follow instructions will walk you through the entire repair procedure.

The Time-Sert 5553-8 is considered by most professional mechanics to be the best Ford Triton spark plug repair kit available. This kit can also be used for Double Over sized if previously repaired.

check price of Time-Sert F0RD Triton Spark Plug Repair Kit 5553-8 w/ 8 Inserts at amazon



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