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TIME-SERT 1812COREBS Rocker Bolt Hole Thread Repair Kit M8x1.25

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In Stock
2.00 LBS
  • 1812CORE Big Sert is for repairs when a Helicoil has failed making the hole bigger
  • Time Sert 1812CoreBS Big Sert


This is for second time repairs when a Helicoil or other brand has failed leaving a larger hole to be repaired. Since it is oversize the the outside diameter of the inserts are larger in diameter allowing a second chance to repair holes that were previously repaired.

This tooling has been used in rocker arm thread repair where the threads must start a few millimeters deep below a "Slot".

The core drill countersink combination will have to set by hand. We use this special 4 flute core drill because it makes drilling through the line-up slot easy. Using a traditional 2 flute is difficult because the drill it tends to hang on the slot and break.  *When installing BIG-SERT inserts do NOT back up. Use a continuous right hand rotation of the install driver tool.

Instructions Included:


1. Step Core Drill w/collar

2. Tap

3. Insert Driver

4. Tap guide 75825

5. Inserts qty 5 part number 58121

6. Hex Key 55516


1812CORE pdf Instructions


 Related Products

TIME-SERT Big Sert 58121- Replacement Inserts for 1812CORE BS 

*Note, some GM engines use a 10mm rocker arm bolt. Please verify your bolt size before ordering.    

Mouse over the images above for a more detailed view of the kit components. Also notice our bulk discount prices on TIME-SERT replacement inserts for thread repair kits. Need more information on TIME-SERT thread repair kits? Visit our auto repair blog section on thread repair kits for tips, advice and all your thread repair questions answered. Just comment and we will be quick to respond.

See the pdficon-small.png TIME-SERT products pdf for more information on thread repair kits and inserts. Some are listed for certain applications on cars, trucks and motorcycles. The pdf is a partial application list so feel free to email or call if we can assist with your particular need. We also accept inquiries regarding our daily TIME-SERT specials. Remember TIME-SERT is recommended by leading car manufacturers like the General Motors Corporation. In fact TIME-SERT is GM's only authorized repair for head bolt threads.

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1 Review

  • 5

    Best FIX!

    Posted by Jesus A on 22nd Sep 2015

    Fixed threads for rocker arm on my 3.4 Chevy. Much better than other repairs that I looked at.

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