head bold repair kit

Buy a Manufacture Specific Head Bolt Repair Kit for $450 & Up or Use This Head Bold Thread Repair Method for About $90

We get a lot of calls from people who go to put their cylinder head(s) back on the engine (aluminum block) and the threads strip while trying to torque the head bolts. Let’s talk about the different threads first. Standard “shelf item” metric bolts are 6MM, 8MM, 10MM, 12MM etc., all even numbers. The auto manufactures sometimes use the odd number metric threads on some of their fasteners, 5MM, 7MM, 9MM, 11MM etc. Because of that, the people who make thread repair kits have those sizes. Here’s the rub: most of the threads are recessed down in the block, usually 35MM (1 3/8”) to 51MM (2”). The thread repair kits won’t go down that far. You can buy a Time-Sert kit specifically designed to do this very repair for a meager $415.34 and it includes free shipping! Or you can do it this way and spend less than $40, and it’s easy. If you thread the top of the block with a 11MM/1.5 thread pitch, our example below, you can’t buy replacement bolts that are 11MM X 1.5 pitch the correct length (that we could find) to bolt the head to the block. We install 7/16” thread repair inserts instead. They are virtually the same size, .433” versus .437” and we can buy the bolts in ¼” increments. If I’ve confused you, the following example should clear it up.

This example is a 2001 Toyota Camary 2.4 liter DOHC and the Hondas are very similar. I’m not picking on Toyota or Honda. If we were discussing an in-line aluminum BMW 6 cylinder block, I’d start out saying plan on re-threading the block before you even take it apart (it’s 12MM X 1.5 and you can still use the OE head bolts).

The factory head bolt approximately 6 ½” long, 11MM X 1.5 thread pitch. The threads in the block don’t start until approximately 2 ¼” down from the deck of the block, 4 ½” from the head bolt hole in the head.

This is the factory head bolt:

Here is the new head bolt:

head bolt thread repair

time sert head bolt repair

The reason I showed the tap with the new head bolt is a few people have not threaded the hole deep enough. The tap is tapered at the beginning to get it started. If you don’t thread it deep enough the bolt gets tight at the bottom and you can’t get the right head torque, called “clamp load” on the head gasket.

Here’s what you need:

  1. 1-7/16″x 14 TimeSert kit P/N 0761. The inserts that come with kit are not long enough, order P/N 076135 (1″ long) as many as you need( a couple extra probably a good idea).  Here is the installation video link if you like: http://www.timesert.com/html/install.html#1
  2. Installed properly you don’t need loctite. We buy from Neal @ Mechanics Tools, here’s the link:  http://www.mechanicstoolsandbits.com/
  3. Lastly the bolts you need are “Grade 8 Socket Head Cap Screws”. We by the from McMaster-Carr. Here is the link:  http://www.mcmaster.com/#socket-head-cap-screws/=121vu66 .

 Most 11 MM applications take 4″ long, full size such as Camry, Accord etc. Some of the 10 MM applications take 3 1/2″ long such as Civic, Corolla etc.

Here is the block before the repair:
Block Before Repair

Here it is with the insert installed:
Block With Insert Installed

The drill size for the insert is 29/64” (.453”). Since the holes are already .465”, we didn’t even have to drill them. Be sure to use thread cutting fluid or light oil when tapping the threads. Clean the threads with Brake-Kleen or equivalent before using Loctite. In this case you don’t have to worry about where the chips go, these are dead end holes (as most are) meaning they can’t do any harm at the bottom of the hole.

Let the Loctite dry overnight before you assemble. Thread all the bolts all the way through the insert by hand. If there is a bind, remove the insert, re-tap the hole and install a new insert. You can remove the insert by grabbing the end of the top tip of the insert with a pair of needle nose pliers, turning it clockwise wrapping it around the needle nose and spiral the insert out.

The entire job won’t take more than an hour or so. Once you do the first 1 or 2, the rest will go easy.

Hope this helped,

  1. November 25, 2014

    thank you for this info. is this the method and info to use on a 2001 Toyota rav 4 2.0 1azfe engine block? time sert kits are so expensive. trying a less expensive way to fix my car. thanks again

  2. August 12, 2015

    How are the new bolts long enough to screw in?

  3. November 27, 2015

    where to find and what kind of bolts to use as shorter head bolts

  4. January 19, 2016

    2003 2.4 not taken apart yet are the bolts hardened what kind of heads are on them and where to get them mine is leaking from rear should I retread all of them

  5. March 26, 2016

    I just completed a repair using the above info. I torqued the 7/16 X 14 cap screws to 85 ft lbs. Worked very well. Saved some money for the customer. Thanks John for the great info.

  6. February 12, 2017

    How to purchase thred insart

  7. August 15, 2017

    Can I pick up if you in Orlando

  8. August 25, 2017

    Ummm…..the long head head bolts keep the engine block in one piece. Remove the long head bolts and the block is severely weakened.

    It may take a lawsuit to prove this……just think if the engine block explodes while someone is accelerating to get out of the way of a semi using this process. The lawyers will eat your young if they find this web page.

  9. January 18, 2018

    Thank you for this information. Ran across it after requesting a quote for a 6.0 Powerstroke head quote. I have a 2007 Toyota Camry with 2.4 that has this very issue. As a former technician, this repair not only will save money, but is a strong repair. The comment above obviously has no engineering background nor a practical mechanical experience. This repair will not fail, unless the person putting it together does not follow the directions as given. This is a high quality repair. First, the bolts suggested claim to be better than the original bolts used by Toyota. The Timeserts are made from high quality steel, which is better than the aluminum threads supplied by Toyota. (they pull out on a regular basis). Toyota itself recommends the Timesert kit for $400+ to fix this issue, but will not own up to a failure that is totally their liability. With the higher tensile strength insert and bolts to go with it, on top of providing a larger thread size and longer thread into the aluminum block, this is a solid repair from an engineering standpoint. As long as the head and gasket are secured equally across (torqued correctly) the headbolt pattern, they should not fail due to this repair.
    Thanks again for your money saving tip.

  10. March 27, 2018

    I did mine this way. The timeserts are just below the surface of the block. There are two guide pins that will need to be pulled out temporarily. I not recess these holes with the bit provided as I did the others, I just ran the tap in 1/4 inch further. I also put the timesert on a 7/16 bolt with the head cut off and put it in a drill to reduce the stop head to fit into the pin recess hole. I did this so I could re-use the guide pins in the original hole. I also shaved a bit off the pins for clearance sake. Thanks for posting this Southeast!

  11. June 1, 2018

    In my case new head bolts got striped with new helicoils 15 or 15 mm lenght . Many of them they got striped with torque of less than 40FTLB.. So I got that your idea about installing different head bolts and new tread on top of engine block but I was thinking why not reusing my still much new bolts by shortening them for 1-2 inch (cuting them) then installing new helicoils on top of eng. block but longer ones 30mm lenght wich will able (I assuming ) be able hold more torque than 15mm helicoils. Yes exhisting bolts are Torque to yeald type. My problem is Hyundai Santa Fe 3.5 engine 2010 model with Alum . block and 16 problematic head bolts. one of benifits of instaling new helicoiuls on top of head will be no need to remove first set of helicoils because they will not be on way . i would like to hear opinion of other people. Thanks

  12. August 30, 2018

    I have 45 years experience installing inserts and helicoils, I’v built 1200 plus engines. I see your method is appealing to many, but replacing TTY (torque to yield ) headbolts with non TTY headblots changes the clamping load. Also by changing the location of the threads to closer to the deck, you run the rick of cracking blocks. I do echo the comment about liability, those lawyers are crafty and vicious. Thanks for the work you put into this technique as it has many applications in different fields of mechanical repair.

  13. March 6, 2019

    Will this work on the 3.5 kia?? Can I get the right length bolts to do job correctly? Thanks

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