Cam Cap Stud Problems

[2cams70]

I've done some more investigation regarding this using the Lock N Stitch option and here are a couple of possibilities:

From Helicoil charts I have determined that the major tapping diameter for the 5/16" Helicoil insert that has pulled out is 0.3884" (9.87mm). This means that you will need to choose a new insert that has a minor tapping diameter 9.87mm or greater for installation.

Best quality option:
The best option is to use a Full Torque FPS solid plug that is 0.465" diameter and 0.575" in length. The solid plug can be drilled and tapped for the 5/16" stud thread and it can also be bored for the cam cap dowel location. The resulting repair will be perfect, better and stronger than original. The kit part number is FPS30400K.

2nd option:
Use a Full Torque FFT style insert. The extermal diameter is the same as the FPS plug above however it is fully threaded in the middle with a 5/16" thread. You can't really bore it for the cam dowel location. You may hovever be able to cut the dowel down so it doesn't protrude above the cam cap surface. The location accuracy will therefore depend on th fit between the shoulder of the stud and dowel inside the cap. Not ideal but may prove to be sufficient if the dowel location on the other side of the cap is still in good condition. The kit part number is FFT3S51618K

In my opinion the Lock N Stitch method of thread repair is second to none (no affiliation). I'd recommend however that the inserts be inserted by a professional with access to milling equipment, etc. to ensure proper machining accuracy. Refer attachments below.

Welding to fill the hole and re-tapping was not recommended in my case because of the depth of the hole, possible distortion, and due to lack of appropriate heat treatment the weld material would be soft resulting in new threads stripping easily.

[Greg Foster]

The actual dimension of the Heli-coil is .397" The Key lock insert is just right for this size BUT... I'm waiting for a reply from the manufacturer in regards to the application. The remaining dowel should keep the cap allignment quite stable on the cam especially if I don't have to muck with the dowel recess on the damaged hole.
We will see. Not going to make any decision until I have clarity..(may never happen)
Greg

[2cams70]

That FPS solid insert with 0.600" shoulder diameter will have plenty of meat to allow for the machining for the dowel tube at 0.437" diameter. If you aren't so concerned about accommodating for the dowel location then the FFT insert is the obvious choice.

To me the Full Torque inserts are a much better system than Keyserts although admittedly they don't come cheap. They are an OEM repair for Caterpillar Diesel Engines and typically heavy duty Diesel engines have at least a 1,000,000 mile design life. They really are a "Rolls Royce" thread repair.

The inserts themselves usually aren't that expensive but the tooling is more so. If the workshop you use already has the tooling then the cost should me minimized. Any Caterpillar or maybe Cummins Diesel engine workshops in your area?

P.S. Hmm... looking at your diagram the shoulder on the FPS insert will likely encroach upon the cam bearing seating area which will require a line bore of the tunnels to correct. Maybe an FFT insert is better in that case. Whatever insert you choose however will need to checked for clearance in that area.

[Greg Foster]

After obtaining the Key Lock Inserts and looking over the instructions, I decided to remove the drive pins as you can see above the stud. A .397" or size X drill bit was required for the Key Lock bore and I already had that when the helicoil popped out. I deepend the bore with a size X drill so the insert would sit low enough in the head to allow the cam cap dowel room to seat. I cut the stud bore with a standard 7/16" x 14tpi tap as per directions. I then used a bottom tap of the same size, cutting the threads deeper in the bore. This gave me room for the hollow dowel.
I then attached the Key lock to the studs coarse threads with sleeve locker making sure the Key Lock insert was deep enough in its location on the stud, when the stud was installed in the head, to accommodate the cam cap. See picture of the stud installed. From there on it was install the modified stud in the head and install the cam cap. Of course all the swarf and debris was cleared from the bore prior to installing the stud.

[Greg Foster]

Here is the end result. Cam cap good as new. Torqued to 9 ft#. This was much easier than I thought, especially with the good input of ideas. Instead of having a stud made with oversized threads to fit the hole, I used the standard stud and the Keylock. And I didn't have to modify the stud hole.... peace of mind.
Thanks for all the input.
Greg

[2cams70]

Great! Thanks for sharing the resolution.

[SJ Lambert]

Fantastic result Greg!

I have a handful of similar keyserts that I intend to use on a magnesium spacer plate (bell housing) - it's gear box mounting holes have been flogged out severely.

The plate is a spare at the moment - so I'm currently not motivated to repair it, but it's nice to see you getting a first rate result in aluminium!!!

Cheers

James

[512BB]

Yes, that looks like a very nice job Greg, well done. A problem like the one you had is so satisfying when it comes out right in the end. I do not know if you have replaced the cam cover yet, but check and triple check that you have indeed removed all the swarf. Maybe hang a small but powerful magnet in there if you have one.

Leslie

[Greg Foster]

I have made sure all the metal shavings have been removed. Nice and clean.
Greg

[billwill]

Leslie, what would be the use of a magnet on aluminium swarf?