Cam carrier studs size

[peteyg]

Oh joy! Whilst refitting the exhaust cam carrier, two of the studs decided to make a bid for freedom taking part of the head with them. Can anyone give me the size and pitch for the  studs so I can look into helicoiling. Hoping to do it in situ without removing the head. Anyone successfully done this? Irritatingly they are at the pulley end so a little less wiggle room without crouching over the engine.

Pete

[andydclements]

I'm pretty sure they are M8, certain they are metric, and certain it's the "standard" thread rate for the size (i.e 1.25m if 8mm).

[sailorbob]

As the same M8 nuts (part no. A075W3021Z) are used on the early cam carriers that use 20 studs and the later cam carriers that use 4 studs (M8 x 1.25 x 60 mm) and 16 E10 Torx bolts it's safe to assume they are M8 x 1.25 studs.

Edited July 10, 2018 by sailorbob

[CarBuff]

Pulling the threads out is a common occurrence. 😵

 

Many of us prefer Time-Serts to helicoils .

 

http://www.timesert.com/

https://www.baggersmag.com/time-sert-vs-helicoil

 

[Sparky]

Haven't found an engineer that doesn't hate Time-Serts.  Personally, I'll never touch one again after seeing what they'd done to a head earlier this year.  When a Time-Sert slips (and several did) you're left with a bloody big hole that's almost irrepairable.

[Paul Coleman]

11 hours ago, peteyg said:

Oh joy! Whilst refitting the exhaust cam carrier, two of the studs decided to make a bid for freedom taking part of the head with them. Can anyone give me the size and pitch for the  studs so I can look into helicoiling. Hoping to do it in situ without removing the head. Anyone successfully done this? Irritatingly they are at the pulley end so a little less wiggle room without crouching over the engine.

Pete

Pete, if you don't get an answer let me know as I have an S1 head off the car at the moment with all the studs out. I can measure but not until later on.

[molemot]

It can be done in situ...got to be very careful about swarf and keeping the drilling at 90 deg. to the face. All down to the skill level of the operator...

[CHANGES]

4 minutes ago, molemot said:

It can be done in situ...got to be very careful about swarf and keeping the drilling at 90 deg. to the face. All down to the skill level of the operator...

I use a drill jig set up, it makes sure its 90' without the guess work..  I have several jigs now for various applications ..  They are easy to manufacture and make the job straight forward.  Its well worth taking a little extra time making one on the bench , you will save so much more time on the job..     All you need is some 10mm flat plate.  Drill m8 on bench press to keep straight matching holes on the application ... drill the hole needed for H/ coil to that size needed . bolt to head with other holes then drill head using the jig as a guide ..   If needed you can also make a threaded jig for taping the H/coil insert , just to be sure its square..  its a bitch when it ain't.    Small tip .. I also  wrap some tank tape around the jig to make a wall to stop the swarf  spreading when done in situ..  works a treat.. 

[mike_sekinger]

Excellent advice - something like this for exhaust manifold thread repair

[molemot]

4 hours ago, CHANGES said:

I use a drill jig set up, it makes sure its 90' without the guess work..  I have several jigs now for various applications ..  They are easy to manufacture and make the job straight forward.  Its well worth taking a little extra time making one on the bench , you will save so much more time on the job..     All you need is some 10mm flat plate.  Drill m8 on bench press to keep straight matching holes on the application ... drill the hole needed for H/ coil to that size needed . bolt to head with other holes then drill head using the jig as a guide ..   If needed you can also make a threaded jig for taping the H/coil insert , just to be sure its square..  its a bitch when it ain't.    Small tip .. I also  wrap some tank tape around the jig to make a wall to stop the swarf  spreading when done in situ..  works a treat.. 

Pretty much exactly what I ended up doing...drill jig is the way to go. Have seen it done freehand, but would rather use engineering than hope the skillset stretches to that! I have a number of special tools I have made up over the decades...one for pressing back the rear caliper pistons painlessly...some for greasing bearings...cylinder liner extractors, etc.etc.

[peteyg]

Great advice all, thanks! @CHANGES have you got a pic of your jig setup?

Pete

[peteyg]

Well, here's what I have fashioned so far. Picked up helicoils today so will crack on when I have a moment. Nice thing is that the studs top and bottom match in reverse so the same jig can be used for both!

IMAG2076 (1) by

IMAG2074 by

 

[peteyg]

So my first attempt at drilling and helicoiling in situ was a 75% success. Drilling went fine with the jig. The first helicoil I made another jig for and tapped a thread but the result was a slightly angled stud in the end but the cam carrier just about fits on with a little wiggling. Not ideal but not much option. The second hole threaded perfectly and I just lined the tap up by eye, no fancy jig. Lesson learned.