Ford Spark Plug Blow Outs – Oversize Inserts and FAQ’s

11:18 am Auto Specialty Tools, Calvan Tools, Ford Problems, How To Auto Repair, Mechanics Tools


Calvan 11/16″ drill bit used with air ratchet and 1/2″ socket.

DenLors tools has sold hundreds of the Calvan spark plug repair kits and has had no reported failures. We’ve answered many questions about Ford spark plug thread repairs over the last couple of years and have included them in various places on our site. Now in this auto repair blog ALL of the frequently asked questions to date are posted here in one central location, if you don’t see your question answered, feel free to use the comment form and ask. Included here are questions about repairing spark plug holes after Lisle, Napa, Auto Zone, or other brands may be thicker than the Heli-Coil, but still have managed to fail and allow the spark plug to blow out AGAIN. We are not out to discredit any other spark plug insert company, we just know from our customer feedback what works and what just works for awhile. The questions below answer questions from real customers with this serious problem. We recommend the Calvan Ford spark plug insert repair kit as the best solution for Ford 1998-2004 4.6, 5.4. 6.8 SOHC (2 valve) engines, the following will help show why.

Question:  Are there different size or oversize inserts available for the Calvan insert tool and are they included?

Answer:  There is only one size thread insert for the Calvan repair kit and 6 are included. There is only one size because once the Cal Van is installed, it will not blow out and there is no need for an oversize insert. The Calvan insert is larger than competitive brands and Cal Van’s larger stronger design is one of the reasons it can last the life of the cylinder head.  To date the Calvan insert is the largest insert available, that’s the reason it can be used when other brands fail.  

Question:  I have a 1999 Ford F150 with a 4.6 liter Triton engine with 126,000 miles on it. The number 3 spark plug blew out of the cylinder head. I called my local repair shop and was told that this was a common problem with this design engine because of the extremely thin (aluminum) casting in the spark plug area of the engine head, there is only about five threads for a spark plug. How is the Calvan insert better?

Answer:  While it is true there are only five threads for the spark plug in this design engine for the spark plug and the Calvan repair insert has five spark plug threads as well, the Calvan spark plug insert is steel not aluminum and the insert itself is held in place with ten external threads. The Calvan spark plug insert improves the design and durability at fraction of the cost of replacing the cylinder heads; and if replacing the heads they would have the same design weakness.

Question:  I am selling my truck as fast as I can get a spark plug to stay in long enough to get rid of it. I wanted to use a Heli-Coil because I won’t have to drill, but the thread tool isn’t long enough to reach in the spark plug recess, any suggestions?

Answer:  I personally recommend the Calvan spark plug repair kit because it is a better repair, but if you would rather use the thinner Heli-coil insert, the HEL5396-14 has the longer thread tool than the standard Heli-coil kit.

Question:  I have Ford van that has had a parts store insert installed previously, it has blown out and I want to know if the Calvan insert will work since the old insert has left a bigger hole now?

Answer:  Yes, the Calvan spark plug repair insert is larger and has worked well for our customers before, saving the expense of replacing the heads. Read on for more information.

Question:  I bought a rebuilt head and come to find out one of the spark plug holes had a repair insert, it blew out last week. The cylinder head has a warranty, but I cannot afford the down time of pulling thread all over again. Will the Calvan insert repair this hole?

Answer:  Yes, the Calvan insert is a thicker beefier repair that you don’t have to worry about. And I always tell our customers that when purchasing a rebuilt head of this type to be aware of the possibility that inferior repair inserts may be in the head. Buying a brand new head would insure that there are no cheap inserts, but you would be stuck with the original weak design. The Calvan thread insert repair saves down time, money and is stronger due to the material being steel alloy instead of aluminum like the original threads.

Question:  I need to know the size or dimension of the outside of the insert, to know if it will be large enough to repair the spark plug hole threads that have already been fixed once before?

Answer:  The outside diameter of the insert is .73″ or 18.65mm, this is measuring on the most outer part of the threads. If a HeliCoil or regular size Timesert (not a Big Sert) was used before in the original repair this will work well. 

Question:  I have an insert that blew out after an engine rebuild, I can’t afford the down time to have the engine pulled AGAIN. The insert that’s still on the spark plug is not a thin Heli-Coil, it appears to be a bigger insert, maybe an oversized thread repair. My question is; Will the Calvan thread insert work in an engine after the bigger insert has blown out? The outside diameter of the bigger insert is .63″ or 16mm.

Answer:  Yes, I can say this because the drill bit included in the Calvan 38900 spark plug repair kit is 11/16″ (.6875″ or 17.4mm) so what you’re telling me is you have a smaller hole than what the drill bit size is in our kit. So as long as the previous repair was drilled in the center, the Calvan will work great. Also the Calvan has a guide that fits in the spark plug recess so drilling and tapping will be centered every time, if you have a good view of where you’re working or not.

Question:  Does the CalVan insert accept the same spark plug or will I have to remember to use a different spark plug in the repaired port?

Answer:  The CalVan insert uses the same spark plug and has the identical taper and same number of threads, just stronger steel not aluminum.

Question:   The price for one insert seems high, are you sure I don’t get more than one insert for this price?

Answer:   I understand this seems like a lot but for an insert of this quality it’s like many things in life, you get what you pay for. Who wants to trust a weaker design insert to hold in a spark plug, if it fails on a coil over plug design it may break a $50 plus coil, require the job to be done over again, or worse cause extensive engine damage requiring the replacement of the head.

Question:  How long will the Calvan spark plug repair last?

Answer:  The Calvan inserts are designed to last the lifetime of the engine and are stronger than the original threads.


Calvan’s leak down tool to determine when the valves are closed.

Question:  Time Sert says “The only 100% way to know the valves are not open is to remove the valve cover and inspect the cam, making sure that it is not depressing the valves on the damaged spark plug hole.” Do I have to remove the valve cover with the Calvan Ford spark plug insert tool kit?

Answer:  No. The Calvan tool kit allows the mechanic to verify valves are closed with an included cylinder leak detector. Plug the rubber stopper from the leak detector into the spark plug hole with a low amount of air from an air compressor going through the hose. The rubber cone will pop out of the spark plug hole when the valves are closed. The video shows this as well.

Question:  How do I know all the aluminum metal shavings are out of the cylinder?

Answer:  A borescope is used to make sure all foreign debris is removed. A video inspection scope can be used as well, we have a fairly inexpensive video based scope, that in our opinion is better and easier to view than the fiber optic borescope shown in use in the instructional video.


Calvan’s metal sleeve or guide is used to center the drill bit and the tap.

Question:  I’m afraid I might start drilling or tapping the hole crooked, am I going to damage my head beyond repair?

Answer:  With the Calvan specialty tool kit that we sell, since it is made specifically for Ford 4.6, 5.4 and 6.8 Triton engines, it has a guide that fits into the spark plug recess to perfectly guide the drill and the tap making the repair centered, even in hard to access areas.

Question:  Will my spark plug be properly grounded through the engine, since the insert will have JB weld on the threads?

Answer:  I’ve only had one person ask this. The answer is yes. JB weld or Loctite with some other brand inserts is being used on the threads, but there is a large enough percentage of metal to metal contact that provides ground, to allow proper firing of the spark plug.

Question:  The Ford cylinder repair kit instructional video (showing the repair done with the engine on a stand) is good, but can this repair be done in the vehicle?

Answer:  Yes, the video is showing how the kit is used with an engine on a stand, however the tool kit is designed to be used on an engine that is in the vehicle.

Question:  There doesn’t seem to be much room under the cowl area of my truck. How can I drill in that tight area?

Answer:  This repair kit is used in tight areas, on trucks and even in vans. The drill bit, which is used in the guide so the hole is drilled in the correct position. And to allow drilling to be done in confined areas, the drilling is actually done with an air ratchet. The drill bit accepts a 1/2″  socket that is used with your air ratchet, so drilling is done on a right angle. The guide is also used with the thread tap, so making a perfectly centered hole is easy.

Question:  On the CAL38900 – Hi, I’ve got a 1998 Ford E350 w. Triton v10 (6.8L) with a blown plug ( second from the front on drivers side.) I’m just wondering what length the tap tool is? I only have about 6-8″ above the engine to work with and was hoping I could do this without dropping the engine. Also, is there any special type of air-ratchet I should use on the job?

Answer:  I understand your concern. This kit is designed to be used in the vehicle, even in vans. The length of the tap is 7 3/8″ long. The bit is 7″ long. A 3/8″ air ratchet like the Ingersoll Rand 109xpa works well.

Question: I am working on a motor that has had a cheap parts store brand insert installed. The problem is there’s a holes burned along the side of the hole. I’m not sure if the Calvan insert is big enough to take care of that extra width. Is there a larger insert available?

Answer:  Yes. But first since you already have the Calvan kit I would try it first. The top of the Calvan insert has a shoulder that may help seal up the extra hole that was burned through from driving the vehicle with the compression leak along the side of the part’s store insert. If there is still a compression leak heard, after trying the Calvan insert I would turn the motor off quickly to prevent burning an even larger hole beside the insert. We have the Time Sert 5600 which uses an insert inside another insert to end up with the largest outside diameter possible. See the following listing for more information on the largest Ford Spark Plug Thread Repair kit available. It requires the entire kit because it is larger, but it’s still better than pulling the head and replacing it.

Related Links and Products

Ford Spark Plug Blow Out Problems How to Repair – Original article

Calvan 38900 Insert Kit – Product in this blog for sale.  

Calvan 389-100 DLT Inserts – Additional inserts sold separately.

Expedition Cylinder Head Removal w/Body Off – NOT required with the 38900 DLT see what you’re missing 

Time-Sert and Big Sert Thread Repair Kits – FAQ’s

Difference in Lengths for 5553 and 38900 Reamers

130 Responses
  1. dennisb - Auto Tool Sales :

    Date: September 28, 2012 @ 12:11 pm

    Andy, I would not attempt this job without compressed air available. You need a compressor for the air ratchet. I would also use the shop air to blow off the engine and tooling. Good Luck.

  2. Roland :

    Date: October 3, 2012 @ 5:28 pm

    #3 plug blew out and appears to have been repaired with helicoil insert, I have purchased Cal38900 and awaiting arrival, does the intake have to be removed from the 5.4 engine.

  3. dennisb - Auto Tool Sales :

    Date: October 3, 2012 @ 8:13 pm

    Roland, no the intake stays on. Check out or FAQ’s for more info while you are waiting on delivery. Thanks.

  4. Richard :

    Date: December 8, 2012 @ 4:10 pm

    Hi Dennisb. We have a 1998 lincoln Continental w/ a 4.6 36 valve engine.
    “front of car” spark plug blew out, so real easy to get to. We have the Calvin repair kit and have fixed may Ford issues with it. The Lincoln 4.6 liter engine spark plug tube is to deep for the Calvin tools to reach the spark plug hole. Will the Time-sert 5553 work for this engine? Thanks. Rich Cobb.

  5. dennisb - Auto Tool Sales :

    Date: December 8, 2012 @ 7:54 pm

    Hey Richard. Yes, the Time Sert 5553 is the one to use for the Lincoln Continental. Let me know if I can assist you any further. BTW, checked our your business website at Great story. I like to see small businesses adapt and do well.

  6. Joey :

    Date: December 12, 2012 @ 1:12 am

    Hey Dennis I have a 1999 F250 with a 5.4 triton and it had a heli-coil that blew out with the spark plug, so I took it to a dealership and they said I would have to get a new engine. My grandpa was a mechanic and asked me if I could put a oversized spark plug, what would work best.
    Thanks in Advance

  7. dennisb - Auto Tool Sales :

    Date: December 12, 2012 @ 7:01 am

    Joey, Thank God for Grandpas! There is another option that allows you to use the same size spark plug. I would use the Calvan 38900. It uses an over-size thread insert (that fixes ports damaged by Heli-Coil failures) that accepts the same spark plug. Let me know if I can ships one of these kits for you today. You may also just order it on-line anytime by clicking on the following and checking out – Calvan 38900 Spark Plug Repair Kit.

  8. Martin :

    Date: December 24, 2012 @ 1:52 am

    I would like to take the time to comment on the Calvan 38900 kit I purchased. I have a 2002 Ford F-150 5.4L that blew out one of its spark plugs. I had no idea that these engines were prone to this problem.After researching this problem on line I ordered the Calvan kit. Within 3 days I had the kit in hand and made the repair. The repair was so simple and the end result was better than factory. I would not hesitate to recommend this kit to anyone that has this problem. This is a high quality kit and is everything the company said it would be. One question ,can I buy more inserts if I should ever need them? Thanks for a great product.

  9. dennisb - Auto Tool Sales :

    Date: December 24, 2012 @ 9:42 am

    Martin, thanks for taking time to comment. We sell the replacement inserts also, see the link below by clicking on the image.
    Calvan reploacement inserts.

  10. Frank :

    Date: February 19, 2013 @ 12:48 pm

    I have 2003 F250 V10. It has blown the previous Heli coil. will this product work?

  11. dennisb - Auto Tool Sales :

    Date: February 19, 2013 @ 12:54 pm

    For the Triton engine like you have, the short answer is yes. We sell them all the time for repairing holes that were previously Heli-Coiled and have done so since 2005 with no reported failures. The drill bit that comes in the kit is 11/16″. If you have any doubt or want to double check to make sure the hole is not too large already, place an 11/16″ drill bit in the hole. If the hole is smaller than the bit, the kit will work fine. This is because you will be drilling the hole out with the 11/16″ bit before tapping it anyway. After drilling and tapping the hole; it will accept the new spark plug insert. Our inserts are not a temporary repair. They will last the lifetime of the engine. As you may have already read the inserts are made of a steel alloy that shares a similar composition or make-up as aluminum, as to not cause grounding or ignition problems; but has a much higher tensile strength compared to aluminum.

  12. les :

    Date: February 23, 2013 @ 3:17 pm

    I think my insert is 18mm came out a second time what can I do to fix it do they make bigger ones?

  13. steveo :

    Date: April 29, 2013 @ 2:30 pm

    Hello, I just purchased the cal van 38900 because it was less expensive than the time sert product. I am working on an 03 Ford escape with a 24v 3.0l. I assume this product will work since the same timesert kit works on this engine as well as the 4.6, 5.4 etc… Is this correct? Thanks

  14. dennisb - Auto Tool Sales :

    Date: April 29, 2013 @ 2:43 pm

    No, the Calvan is made specifically for certain years of the Triton engine. The insert might work but the tooling is not designed for your engine. We sell the Time Sert 5553 for your application because the tooling lines up differently. It uses a stepped design bit and tap. The Calvan uses a line up piece that is not made for anything but the Triton.

  15. steveo :

    Date: April 29, 2013 @ 10:04 pm

    Thanks for the info. Will be ordering the timesert kit. Will there be a problem returning the calvan unit?

  16. dennisb - Auto Tool Sales :

    Date: April 30, 2013 @ 7:57 am

    Steve, I have emailed return instructions detailing the restocking fee and return address. Thanks again.

  17. Goldfishdigger :

    Date: May 7, 2013 @ 1:39 pm

    I have a 2006 Ford Police Vehicle that had 82,000 miles on it when it first broke and the garage fixed it with the above kit and methods. The vehicle now has 85,000+ miles and the same plug blew again. Now the garage wants to fix it again using the same methods. This is a police vehicle and usually always on the go. Do i expect to be driving a loud VW in another 3,000 miles…

  18. dennisb - Auto Tool Sales :

    Date: May 7, 2013 @ 2:14 pm

    Seems like very low miles for a Police vehicle. Wasn’t it Einstein that said “Doing the same thing over again and again and expecting different results the definition of insanity”? Regardless, I would use one of our kits either the Calvan 38900 (SOHC) or the Time Sert 5553 (works on both SOHC and DOHC) and be done with the problem. Our kits are oversized so the hole can be larger and still be repaired. The Calvan inserts are slightly larger measuring the outside diameter at .73′ compared to Time Sert’s Big Sert inserts at .69″. An 11/16″ drill bit can be used as a gauge. If the hole is larger than an 11/16″ drill bit before starting there is another option. The 5553 and the 5588 can be used together to place an insert inside an insert bringing the outside diameter of the largest insert at .77″. This rarely needs to be done but it’s good to know there’s another option before the last resort of discarding the cylinder head. Good Luck.

    Insert in an insert from 5553 and 5588 kits.

  19. Skip :

    Date: June 27, 2013 @ 10:46 am

    I have to say this was a life saver. My son returned to see me on fathers day before he was deployed again overseas. On his first night back he had a typical spark plug failure on his expedition. We tried one of the over the counter methods and it failed within 10 minutes. We are on a very limited budget and I was hesitant to purchase another tool but this is probably the only product that worked just as described. Even a novice wrench turner can make this work. It took about an hour and has worked great. All I can say if you have a failure on your vehicle that there is nothing else I would try. Thanks Again you made my son and my American Hero very happy with your product. Thanks Again

  20. dennisb - Auto Tool Sales :

    Date: June 27, 2013 @ 10:49 am

    Thanks Skip. And give your son a big THANK-YOU from us for his service!

  21. dave m :

    Date: October 8, 2013 @ 9:23 pm

    I,ve read all questions and comments but have not heard any mention of “lock and stitch” methods of repair as Ford recommends as a non warranty repair. 03 expidition 5.4 has had 3 done on #3 cyl. The first 2 inserts blew out and this one has a combustion leak (audible) which is misfiring. With the style of repair (hole drilled and pin inserted to lock insert) will cal 38900 work? p/s I would not recommend using antisieze on plug threads, modern plugs do not need. Reference Motor Age magazine. Sorry don’t have the mag here for date.

  22. dennisb - Auto Tool Sales :

    Date: October 9, 2013 @ 7:37 am

    Dave, Lock-n-Stitch is a thread repair system that I haven’t had too many questions on. My impression is that besides being a very expensive thread repair, is that it works OK in most cases. As far as the repeated failure of the LocknStitch inserts in your case, I suspect it has something to do with the locking pin. As you know, Lock n Stitch uses a special guide to drill a tiny hole beside the insert and then a tiny locking pin is installed. Since your Lock n Stitch inserts keep blowing back out;  the hole for the pin may be too large now. And the combustion leak that you have (with your 3rd Lock N Stitch insert) is usually a pre-cursor to a spark plug blowout.

    Lock n Stitch has failed to post the measurements on the outside diameter of their inserts on the website. The increased area where the drilling was done for their locking pin also has to be considered. If you have a Lock N Stitch insert and a locking pin, I would measure their combined O.D. (Outside Diameter). That would give you an idea what the overall outside diameter is, with the exception of allowing a little for the wallowed pin hole.  Then it can be decided which kit can be used (if any). Below are the measurements of the O.D. of the inserts in the kits we sell.
    Calvan 38900 – .73″
    TIME-SERT 5553 – .68″ (if someone already has the 5553 kit – a 5588 kit can be used in conjunction to achieve what the kit below does).
    TIME-SERT 5600 – .76 This kit installs a Big Sert inside a triple oversize insert achieving the largest outside diameter made for Ford Spark Plug blowout repairs. If this one is not large enough, the cylinder head would need to be replaced.

  23. Kelly :

    Date: October 29, 2013 @ 11:48 pm

    I just put in my 3rd insert from your Calvan kit. First 2 have worked flawlessly. After I had the insert and sparkplug in the hole, I realized I had used JB Kwik instead of regular JB. Will that cause any problems?
    I know the engine runs too warm for the Kwik but didn’t if it would drip out or cause other problems.

  24. dennisb - Auto Tool Sales :

    Date: October 30, 2013 @ 8:46 am

    Hello Kelly. JB KwikWeld withstands temperatures of up to 300 degrees Fahrenheit. The spark plug can reach close to 850 degrees Fahrenheit. But, I wouldn’t remove the insert just to use the correct JB Weld. The JB weld in my opinion is to help insure the insert won’t back out the next time the spark plug is changed. So one thing you could do is see if the insert comes out with the spark plug. If it doesn’t, I personally wouldn’t worry about it. Let me know if there’s anything else we can assist you with.

  25. Barry :

    Date: November 12, 2013 @ 10:06 am

    Will this tool work on a Chevrolet 1998 S10 pickup? 2.2 4 cyl eng that has already had the healy coil method, has blown out after 100,000 miles. Already did retap once with old tool, and wouldn’t take. HELP!!!!!!

  26. dennisb - Auto Tool Sales :

    Date: November 12, 2013 @ 11:09 am

    Barry, the Calvan is only for Fords. But the Time Sert 5553 will work. It has an outside diameter of .68 measuring on the threads largest part.
    Time Sert 5553

    If that’s not big enough we also have the Time Sert 5600 which measures .75 on the largest part of the outside diameter. It puts an insert inside another insert to achieve this large OD (Outside Diameter).
    Time Sert 5600 Kit

  27. skills :

    Date: May 2, 2015 @ 3:48 pm

    Hi, i have a 2V 6.8 with a thrown plug, i put a 11/16 drill bit down the hole and it went through, how would i know if i cant fix the hole….is there a certain size drill bit that will tell me if the hole cant be fixed, and if so what size drill bit would be the indicator that the hole cant be fixed? thanks

  28. dennisb - Auto Tool Sales :

    Date: May 2, 2015 @ 7:04 pm

    The largest kit we have goes up to about 3/4″ of an inch. You may be able to add thickness to the 11/16″ drill bit with painters tape until it reaches the size of the hole, then measure it. Call if you need assistance at 800-524-9783 10-5 Eastern Time.

    Time Sert 5600 – Stand Alone Kit that repairs spark plug holes larger than .663″ (16.8mm).

    Uses one insert insert another one. 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.

  29. Lupe Montelongo :

    Date: September 27, 2015 @ 2:15 am

    I have 47 years experience on auto repairs, but never before I had come across with a problem like this, a customer brought me his 1998 Pontiac Starfire 2.2 liter engine. The engine was popping and missing, I checked it and it was spark plug #2 that was loose, I have fixed other cars with this problem, I told him that I will fix it, for my surprise when I tried to take the plug out it just kept on turning. So I called him and asked him if someone else had worked on it and he said “yea”. I answer well he messed up your cylinder head because he used an 18MM and put some kind of sleeves which I have a lot of trouble getting them out and saw the spark plug port that it was too large, so I told him that there wasn’t anything that I could do for it but replace the cylinder head, he said that he didn’t have to much money I feel sorry for the guy, but what can I do! If only there were some oversize Helicoils just to help him out. If you have any other ideas let me know. I will appreciate it. Thank you Lupe M.

  30. dennisb - Auto Tool Sales :

    Date: September 27, 2015 @ 9:37 am

    Lupe, If you can measure the outside diameter of the failed insert you’ll have a good idea of the size of the hole. Hopefully it’s not oblong now. An oblong hole can result from leaking compression (and fire) from the combustion chamber which can act as a blow torch. You may want to check with an inspection camera if you suspect it’s been ran like that for very long.

    The largest spark plug thread repair kit is the Time Sert 5600. The outside diameter is almost 3/4″. It’s usually sold for Fords (since they seem to have this problem most often) but since the tooling is lined up with a stepped design (smaller at the first part of the tools) to help pilot them in straight it doesn’t matter what make the car/truck is as long as it takes a M14x1.25 spark plug (which is the most common size). Taper seat inserts are included in the kit and washer seat inserts are available separately. Time Sert 5600 – Stand Alone Kit repairs spark plug holes larger than .663″ (16.8mm). The outside diameter of the largest insert is .77″ – it’s Triple Over-sized.

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