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    Spark Plug Thread Repair Do’s and Don’ts

    Spark plug threads in an engine can deteriorate when they’re loose due to vibration, resulting in a sparkplug blowout. Aluminum threads in the cylinder head can also be damaged if cross threaded or “seize” due to dislike metals. Ford 2V engines typically have the “spark plug blowout problem” and Ford 3V engines are notorious for having stuck spark plugs that can often break when removing them. Cylinder heads can sustain thread damage to the threads, even when following TSB procedures which call for working the plugs back and forth. Whatever the reason for repairing damaged spark plug threads, the following do’s and don’ts may just help complete the job with a long lasting repair.


    1. Don’t resort to using a parts store repair. Yeah, parts stores have repairs readily available but in our experience they are just temporary repairs that end up making holes bigger. Then an oversize repair is needed to clean up the mess. Parts store kits that commonly fail are Dorman and Save- Thread. Any that include “self tapping” or striking from the top are likely to fail sooner rather than later. If you’ve already used one of the temporary kits we most likely can still help.
    2. Don’t work on the spark plug hole without first making sure the valves are closed. Open valves can be damaged by tooling and when blowing shavings out, open valves can allow debris further into the engine.
    3. Don’t use anti-seize on the spark plug. Using anti seize will affect the torque specs because the plug will turn much easier.
    4. Don’t accept an opinion from a shop that the cylinder head must be changed without checking with us. We’ve been selling these kits that have worked to repair rather large holes successfully. Occasionally holes will be too big because a Dorman repair has leaked compression out along the side of the repair eroding an oblong shape that’s too big. But this is usually not the case. Our repair options are available in oversize and are considered a permanent repair which have stronger threads than original.
    5. Don’t just try using a thread chaser when a spark plug blows out. There has to be enough material to chase and the simple fact that the spark plug blew out indicates there’s damage already done. Chasing and re-installing always ends up in a repeat blowout.
    6. Don’t drive the vehicle with a spark plug blowout or with leaking compression from a parts store insert.


    1. Check with us before throwing in the towel. We have different options depending on the application and what’s been done previously. We have oversize repairs available that can fix rather large holes.
    2. Read instructions carefully before doing the job. We also include extra tips upon request when purchasing kits from us.
    3. Have all tools needed before starting the job. An air compressor, an air ratchet, an air blower and the usual mechanics tools. Also have a good light handy. Brake clean is helpful in carrying out shavings. Remember to change the oil afterwards in case some brake clean goes past the rings. We have more suggestions included in our exclusive tips provided when you write “Tips” at checkout on the phone mention that you’d like to receive our free tips by email. See the kits below if working on a 2V 4.6, 5.4 or 6.8 Ford.

    TIME-SERT 5600 We offer the free Cylinder Leak Tester for determining valves are closed before starting the repair.

    CAL-VAN 38900 Starting at $169 with one insert. $10 more for each additional insert when first buying the kit from us.

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