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

(6 reviews) Write a Review
In Stock
2.00 LBS
Calculated at Checkout
  • 8 mm Bolt size only. 8 mm head does not necessarily mean the bolt is 8 mm.
  • Specifically for GM Rocker Arm Thread Repair M8x1.25
  • Comes with 5 inserts. More available.


This thread repair kit is for rocker arm bolts on some GM 3.1 and 3.4 liter engines that have 8mm bolts. If the 10mm repair is needed see the 1015CORE. Tip: Don't go by the head of the bolt to determine the the size of the bolt. Use a nut or die to see what threads on it, or measure with a digital caliper (micrometer). The 8mm will be approximately 7.80 mm and the 10mm will measure about 9.8 mm. 

This tooling has been used in rocker arm thread repair where the threads must start a few millimeters deep below a "Slot". This kit is for "first time" repairs which means Heli-Coils or a different competing brand, were not used  previously. If a repair has been made before and this is the second repair, see the 1812CORE BS (Big  Sert) kit which is over-sized.

The core drill countersink combination will have to set by hand.
We use this special 4 flute core drill because it makes drilling
thru a slot easy. Using a traditional 2 flute is difficult because the drill
it wants to hang on the slot and break.

1812CORE Instructions Included:


1. Step Core Drill w/collar

2. Tap

3. Tap Guide

4. Insert Driver

6. Inserts pn 18125117N

*Note, some GM engines use use a 10mm rocker arm bolt. Please verify your bolt size before ordering. If repairing the M10x1.5 hole use a 1015CORE Rocker Arm Bolt Hole Thread Repair Kit


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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6 Reviews

  • 5

    Cool Tool

    Posted by Destry B on 15th Feb 2016

    2003 Impala. Skeptical at first, but this tool is really easy to use and does a perfect job.

  • 5

    Top notch.

    Posted by John D. on 18th Nov 2015

    Was able to make the repair on the side of the road.

  • 5

    Great Product

    Posted by Randy J on 1st Oct 2015

    Simple and easy to use. Lived up to expectation!

  • 5

    Better than Helicoil thread repair

    Posted by Stewart S on 31st Jul 2015

    Looked at using the Heli Coil brand to fix bad threads for a rocker arm on a Chevy 3.4 Liter engine. A guy I work with at the GM dealership said that he used a Helicoil before and it failed. The Time Sert thread repair kit uses a solid threaded bushing that looks and feels much stronger than the coil/spring Helicoil method. The repair went great. Now I know Time Sert is better - PERIOD.

  • 5

    Works as advertised

    Posted by Kurt V on 6th May 2015

    Used this kit on a GM 3.4 that had the dreaded stripped out boss for the rocker arms. Following this method seemed much better than the other thread repair choices and it was. Take your time, follow the directions and you will have a successful repair.

  • 4

    1812 kit

    Posted by Carl on 19th Aug 2014

    Very good kit.

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