Full-Torque sparkplug thread repair inserts are made in 12mm, 14mm, 18mm and 7/8-18 thread sizes to repair stripped threads.
They come is various lengths as well as thin
wall and heavy wall styles in both steel and
Inserts for cast iron cylinder heads are made of steel which has the same thermal expansion and heat transfer properties as the cast iron.
Inserts for aluminum heads are made of aluminum and are hard anodized to prevent them from ever stripping again. It is very important to understand that all coil inserts are made of stainless steel which simply transfers heat to slowly to transfer heat fast enough to allow the plug to cool and operate at the prescribed heat range. If a steel insert is used in an aluminum head it will fail to maintain metal to metal contact with the head as the engine heats up. Aluminum expands at a rate of 2.8 times more than steel. The aluminum will simply expand away from the insert and the plug will begin to loose its ability to transfer heat. If the spark plug overheats, pre-ignition and detonation can occur.
Today’s computerized engines are unable to compensate for overheated sparkplugs and poor performance and gas mileage are common side effects of changing the heat transfer ability by using a thread repair device that is made of the wrong metal.
The solution? It is extremely important that the expansion/contraction rate and thermal transfer rate of the insert match the cylinder head. In working with engine and spark plug manufacturers we have had the advantage of testing our inserts using the latest computerized spark plug tip temperature measuring equipment to test and validate these issues with the engine running under various load conditions.
Spark Plug Thread Inserts
Many engine rebuilders and production rebuilders simply upgrade all spark plug holes in the heads with Full-Torque inserts to prevent them from ever failing. Spark plugs can then be installed at a higher torque to prevent them from ever coming loose.
The other common problem of coil and other brand inserts is that they frequently come out with the spark plug the next time you change the plugs. Our insert receive a special locking pin that makes it impossible for them to come out without drilling out the locking pin.
Heavy wall inserts are available for spark plug holes that have been seriously damaged by other failed repair inserts. Our standard thin wall insert will repair most failures of coil type inserts but when a large solid style steel or stainless steel insert comes out and leaves a large stripped hole, Our FST style insert will easily repair the damage better than new.
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