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3.1 And 3.4 GM Rocker Arm Thread Damage

This comes up so frequently that I would like to explain 2 easy fixes that exist in these situations. We have encountered so many people who try to fix these stripped bolt holes themselves and wind up not solving the problem. It is our experience that this usually is from bad advice on how to fix it from who ever (usually those who don't know these methods).

Below is a picture of a cylinder head a customer brought back to our shop on West Anderson Street that he had tried to install over the weekend. In his haste to get the cylinder head installed he wound stripping 2 threads. So after being unsuccessful in repairing one of them, he didn’t even attempt to repair the other head. This image below is the one he attempted to repair. The hole was drilled too big for a Heli-Coil or Time-Sert (our 2nd example).

Image one

We are going to deal with this one first.

The most common method of thread repair is a Heli-Coil (coiled insert). In most instances a Heli-Coli does a satisfactory job. However, I don’t like it for this type of job. For this application I prefer a solid insert such as these shown below:

Image two

The Pioneer insert on the left, the Time-Sert on the right.

As you can see, these are solid inserts versus “coiled” like Heli-Coil. The one on the left is for the oversized repair, one on the right for standard pulled threads. Either of them will work well and the first is probably easier for an individual to get the materials (and cheaper too).

How to install the larger of the 2 inserts:

Items needed:

  1. The Pioneer Inc., Automotive Products insert part# is EL-41. Unfortunately they are normally sold in boxes of 10. If you can’t find a single insert, call us.
  2. 27/64” (.4219”) drill bit
  3. 1/2"X13 tap.

Using the 27/64” drill, drill the rocker bolt tower 7/8” deep from the tip of the drill bit. To be sure to get the right depth, put a piece of tape on the drill at 7/8” from the tip as shown below.

Image three

Tap and thread the hole using a tapping lubricant or equivalent. Clean the threaded hole with Brake Kleen or equivalent. The EL-41 insert has some kind of thread lock compound on it from the factory. I suggest you remove that, clean the insert and apply a small amount Loctite 263 (Red) or equivalent to the insert as well as the top threads of the hole. Screw the insert until it is just below the bottom of the slot the rocker arm pivot fits in the slot pictured below. View from the top is the second picture.

Image four

Image five

Below is the picture of the second failure, the threads were simply stripped out and no one had attempted any repair.

Image six

The second repair is using a Time-Sert kit part# 1812 with part# 18129 insert. The reason I like the Time-Sert repair is the method used to lock the insert in place. The bad news, the kit is around $60 where you’ll probably have less than $20 using the first method.

The only “trick to using this method is to run the counter bore tool deep enough so the shoulder of the insert will be just below the slot for the rocker stand as it is in the previous repair.

Now for the instructions………. I’m going to cheat; here is a link Time-Sert’s website. Scroll down and find the videos: (1) Standard Bolt Repair Demonstration and (2) Standard Bolt Repair Close Up. We also recommend Loctite 263 (red) with this repair.


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Hopefully I have helped somone out with this article, call if we can help in any way.


Southeast Cylinder Head
1438 West Anderson Street
Orlando, FL 32805

Toll Free: 855-791-0132
Phone: 407-730-9777