CAM CARRIER TORX BOLT ISSUE

[giorgio67]

Guys,

I was working on my head yesterday, the IN carrier has been shimmed properly and after a various check I start to sealing the cam carrier to head with Loctite 518.

Well, while torquing down the torx bolts I have discovered that one bolt seems stripped, I cannot torque it at the corret range but only at 16 Lf.

Strange, it was working perfectly while checking shims a lot of time.

So, disassembled again the carrier and found that the bolt on the thread is working correctly with no sign of stripped threads...checked various bolts various time...reassembled the carrier on the head and again the bolt seems stripped, is turning free on the threads with any sign of retention.

ARGHH!!!! what can be?

I'm starting to think at the helicol way...

Any tips?

Thanks

Giorgio

[giorgio67]

Ok. disassembled again the carrier to found the original helicoil totally stripped.....

time to buy a 8mm helicol kit for the job.

:thumbdown: :realmad:

Giorgio

[Simon350S]

Bummer. Hope it's easy enough to fix!

[molemot]

Has it been helicoiled before?? If it has, then the hole will have been drilled out and the special helicoil tap used to create a thread for the helicoil itself to screw into. If you have stripped the helicoil...unlikely to have stripped the actual helicoil insert, as this is hardened steel; more likely to have stripped the thread in the alloy where the helicoil screwed in. If that's what has happened, it won't be a simple matter of drilling and tapping and fitting a helicoil....but you'll need to drill and tap it oversize and fit a special helicoil as a repair. I hope all you've stripped has been the original thread in the alloy....then you can use the normal M8 helicoil kit. When fitting helicoils, you have to drill the hole co-axial with the original...square to the top face of the head where the cam carrier fits. You can do this by eye, if you're confident and competent...or make up a jig to hold the head at the correct angle on a pillar drill. A digital angle gauge is good for this, you can set the drill to be at 90 degrees to the workplate, then use spacers or wedges or something similar under the head and clamp it in place, using the digital angle gauge to get the top face horizontal...90 deg to the drill. Then drill out the hole.... tap the resulting hole with the helicoil tap (some grease on the tap helps) and wind in the helicoil. It's an acquired skill...knowing you, you should be OK. You don't want to get the helicoil stuck half way, as trying to get it out again is a swine. WInding it IN, the coils close up and in it goes; winding it OUT the coils open and it jams solid! 

[giorgio67]

John,

as always great technical post.

I know what you said but....to be sincere I have put some helicoil in the past but this time it's not clear to me what's happen.

I have tried to re-thread the exsting thread of the helicolid with a male tool but nothing, now the hole in the cam is too wide for the 8mm bolt but I have removed a lot of pieces of the old helicoid so I think drilling with the proper 8.3mm drill and oversize the thread with the male tool will be good to fit just a new heli.

I will update soon once received the helicoil kit...

I don't like to take the tapping route...

Giorgio

[Vulcan Grey]

Sounds like you stripped out the aluminum thread.

 

I had the same problem recently.  I went ahead and Helicoiled all of the holes for the cam tower bolts in my head.

 

It is important to always clean the bolt threads, since any gasket material, stuck to the bolt threads, will damage the aluminum threads in the head.

[giorgio67]

Thanks for the pics mate, I have take out a lot of broken steel spiral so I think I need just to refresh the thread and insert a new Helicoil, found that the 8x1.25 helicoil are 12mm long, seems a little bit too short for me...?

Giorgio 

[Vulcan Grey]

12mm long is correct.  Any longer probably will not work.  I actually had to dremel one link off on one that wouldn't screw in all the way, so that the Helicoil didn't stick up too high.

 

Also, what John said about drilling at 90degrees is VERY important!

[fjmuurling]

Below is a link with lots of information about helicoils, I used these. There are even helicoils (twinsert) in which you can put another helicoil. The lengths of the helicoils are 1.0d / 1.5d or 2.0d where d = nominal thread diameter of the coil.

http://www.boellhoff.de/en/de/fasteners/special_fasteners/thread_technology/helicoil.php

[andydclements]

12mm long is correct.  Any longer probably will not work.  I actually had to dremel one link off on one that wouldn't screw in all the way, so that the Helicoil didn't stick up too high.

 

Also, what John said about drilling at 90degrees is VERY important!

AS long as you clean it well afterwards, putting the cam carrier on, with some PVC tape wrapped around the drill to stop it cutting it, you can use the cam carrier as a guide for the 90degrees.

[molemot]

The idea of using the cam carrier as a drilling jig is a good one. Just as long as the helicoil drill fits down the bolt hole in the carrier... iirc it does, but check first! Also, helicoils are available in different lengths, not just one for each diameter. To use longer ones, you obviously have to tap the drilled hole deep enough with the helicoil tap. As I said, it's a matter of experience...the more you do, the easier it gets. Which doesn't help the first time....(!) 

[giorgio67]

I'm intrigued about this:

http://www.specialty-fasteners.co.uk/products/threaded-fasteners-thread-locking/keensert-inserts

 

any experiences?

Giorgio