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Ford’s Last Chance Triple Over Size Spark Plug Thread Repair

Ford’s Last Chance Triple Over Size Spark Plug Thread Repair

DennisB © Summary: Ford spark plug thread repair question about an oversized thread repair insert failing and now the spark plug hole that needs to be repaired is even larger. Faced with the grim possibility of replacing the cylinder head on a Ford 6.8 liter engine Adam decides to ask for advice.

Question: I have a 6.8 Ford that blew a spark plug out, it already had a Time-Sert insert that was installed with a 5553 spark plug thread repair kit. I was wondering what is the diameter of the ones in your Calvan kit? Mine are part number 51459 and measure .668″ and its not big enough now. I got an engine cylinder head, a head gasket set, replacement head bolts, coolant, oil and filter sitting here waiting. I’m almost ready to pull head off and thought I would ask if the Calvan spark plug thread repair kit would work or if there’s a different kit that has even larger over-size inserts? Adam C.

Answer: First let me say that we don’t often hear of a Time Sert thread repair failure. If installed properly the Time-Sert inserts work very well. When installing the TIME-SERT Big Sert’s it’s important not back out the (well oiled) driver installation tool until the insert is fully installed. The bottom of the threads are cold rolled and expands the insert helping to lock it in place from the bottom. Loctite is to be used on all taper seat Big Serts. There’s also a tiny pin that is embedded on all Big Sert inserts; that is one more thing that locks them in.

To answer your question, the Calvan spark plug thread repair kit has inserts that measure .73″. That’s measuring on the outer edge of the threads. That is slightly larger than the .68″ you already have. We do have a bigger option though. The insert in the 5558 Time-Sert kit is .76″ measuring on the outer edge of the threads.

By the way there are 5 inserts that come in the Big Sert 5558 thread repair kit. This is considered a last chance repair because there are no other options that are larger. It does require the use of another kit as well though. The Time-Sert 5553 kit that you may already have. If you don’t have a Big Sert kit yet the less expensive 5141E Kit can be used in conjunction with the 5588 kit. The process involves installing an insert inside an insert. The 55522 insert is installed first using the 5588 add on kit and then installing a 51459 insert from the 5553 kit inside of it. I would definitely opt for this repair and use the 5558 and 5553 or 5141E combo as opposed to pulling the head and replacing it. It’s a lot less work and much less down time for the vehicle. Also, over-all it’s less money for the repair compared to removing and replacing the head with all the associated parts needed, not to mention the labor time. See the link below for the 5558 which is used along with the 5553 kit installing an insert inside another insert.


TIME-SERT 5588 Triple Over Size - This is the add-on kit that requires another primary kit like the 5553

TIME-SERT 5553 Spark Plug Thread Repair - Most popular Time Sert kit we sell usually used on 4.6, 5.4 and 6.8 2V engines.

TIME-SERT 5600 Stand Alone Thread Repair Kit - This is the stand alone kit but does not have tooling for installing the smaller of the two inserts by itself.

TIME-SERT 5678 Add-On Kit for 5600 - Add on kit is used with the 5600. The 5678 allows the installation of the smaller of the two inserts by itself when the triple oversize is not needed.

20th Jul 2021 DennisB

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