stripped out Al. bolt holes

[Wolfmantoo]

I started working on a Toyota pickup with an aluminum head.
The eng. head has 2 stripped out bolt holes for the exhaust manifold.
What is better? Helicoils or re-drill and re-thread?
Or is there something else that can be done without welding on the eng.head?

 

[CoryPad]

Heli-coil should work well for this.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[coughdrop]

I agree with CoryPad. If you were to re-drill & re-thread, you would have to open up the manifold holes and then probably struggle to have enough room for the larger sized nuts!
I have done the helicoilling on my Audi quattro turbo head, where the manifolds have a habit of warping and ripping studs out !
Have fun.

 

[tbuelna]

Wolfmantoo:

Helicoils are CRAP (but they're still better than running a bolt in and out of the aluminum base material). With helicoils, after you've run a bolt in and out of the helicoil-ed hole a couple times, the helicoil usually ends up coming out with the bolt. I highly recommend using a key-locked type insert (Keensert) if you have room in the cylinder head. They are significantly more reliable.

As for redrilling and tapping, you will have to do that anyway to prep the hole for a Keensert or a Helicoil.

Regards,
Terry

 

[coughdrop]

tbuelna is of course correct in his comments, however given the nature of cylinder head castings and the lack of space, it seems prudent to compromise with the Helcicoils. A standard practice is to use "thread-lock" adhesive when inserting the coil, This will allow further occasions of disassembly and reassembly of the manifold without problems. Please note, DO NOT refit the stud into the helicoiled hole until the "thread-lock" has cured.
Alternatively use "Screw-Lock" helicoils to BS 7751.
Cheers,
John.

 

[Flowczar]

I recommend the use of a product called a Time-Sert.

http://www.timesert.com

These have cured the problems associated with the poor strength of a Helicoil and other "cheap" thread repair options.

 

[patprimmer]

My experience is that helicoils regularly fail if not done right, but seldom fail if done right

Regards
pat