DenLorsTools.com Summary: Help finding which oversized spark plug thread repair kit to purchase. Spark plug holes that are made too large for regular thread repairs are usually caused by parts store brand thread repair kits that have failed. When the parts store type inserts don’t hold and the spark plug blows back out again the hole is left even larger than before. This requires an oversized thread repair kit. Sometimes the double oversized kit is not big enough. Fortunately, we have a triple oversized kit that repairs even the largest holes up to almost 3/4″. The inside still accepts the regular M14x1.25 spark plug.

Although parts store thread repair kits are convenient to purchase, they often fail. Sometimes they hold awhile and allow the spark plug to eject while driving down the road again. Or sometimes the parts store insert comes back out when the spark plug is being changed for maintenance. Either way, a Time Sert thread repair kit can be used that will not only provide peace of mind it will save a lot of money too, compared to replacing the entire head. The cost of the head itself is only one factor. There’s a lot of labor to consider when replacing a cylinder head; there’s a head gasket set, coolant and a lot of down time. Make any mistakes when replacing the head and gasket… then do the job all over again. There’s also the possibility, if replacing the head, of getting one with a poor thread repair already in it. This can happen when purchasing a used one or a rebuilt head. Even if purchasing a brand new head the threads will be weaker than if repaired with one of our kits. Our spark plug thread repair kits are considered permanent since we have no reports of failures due to material, workmanship or engineering. The biggest kit is the 5600 listed below. It’s best to only go as large as needed. That’s why many shops that already have a Time Sert 5553 kit will purchase an add-on 5558 kit to be able to use the smaller repair or use the 5588 when larger repairs are needed. The 5600 kit also has the 5688 add-on kit available that allows the installation of only the smaller insert without the need to use the triple oversized one. See the video below, for checking to see if the 5553 kit can be used or if the larger kit will be needed.

Painters tape on a dowel or 1/2″ extension could also be gauged to find out the approximate diameter of a hole is. After a tight fit is obtained, the diameter can be checked with a digital caliper. See the measurements listed below for help in determining which kit to use.

Time Sert 5553 – Repairs spark plug holes smaller than .663″ (16.8mm). The outside diameter of the insert is .69″- it’s Double Over-sized, used on many applications and has a Triton counter-bore needed for some 2001 and up. *Note Add-On Kit 5588 for repairing holes larger than .663″ (16.8mm) repairing holes up to .73″. Works for SOHC and DOHC engines. This kit is Made in the USA.

Time Sert 5600 – Stand Alone Kit that repairs spark plug holes larger than .663″ (16.8mm).The outside diameter of the largest insert is .77″ – it’s Triple Oversized. Used on many applications and has a Triton counter-bore needed for some 2001 and up.*Note Add-On Kit for installing the Double Over-sized inserts for holes smaller than .663″ (16.8mm) is kit number – 5588. Works for SOHC and DOHC engines. This kit is Made in the USA.

The inserts included in these kits are for tapered seat spark plugs like found in Fords. If working on a different type vehicle which uses washer seat plugs we have those available for purchase separately.