Failing helicoils - rocker shaft caps - What now?

[Bart Verbeek]

Dear Fulvistae

I have a problem with the bolts of the rocker shaft caps. Two of the helicoils in the head are broken and are failing now to tighten those caps.

Searching on this forum I found a tread (called: "any Ideas?") where Lancialulu aka Tim H. has/had the same problem.
The solution of using Timesert (www.timesert.com) also failed on Tims engine.

Was this bad luck on Tims engine, or is this not the solution?
If not, what is?
Buying a new (second hand) cylinderhead is an option although I refurbished this one; soo I first want to check the other options....

Is it an option to bore the hole and to use an M10 helicoil oversize (standard M8)?

Would it be possible to rescue the head by machining an alu plug - 'glue' it in place, bore it up and place a new M8 helicoil?

It's a 818302 cylinderhead with 32mm inlet ports for my zagato.

All solutions are welcome.

Bart

[lancialulu]

Bart

I rescued my head by giving it to a cyclinder head repair specialist who repaired by a combination of techniques including welding up and remachining. If the timesert doesnt work (it should) you can get a larger version called a "big sert" from the states. Always care with cap alignment and if the alloy is soft then the repair may fail again. The cost of my repair (it was a 1600 head) was cheaper than a replacement head.

My repair man said the torque specified was 40% over the m8 recommended for helicoil - I guess not only has it to hold down the caps with racing valve springs (1600 again!) but also has an additional "pull" from the rocker cover.

Good luck - but if you have a 1300 you have more options!

Tim

[racing]

Two times i have had the same problem. One times with head on the other with head off
the engine.

I have made my owen repair insert.

You have to pull off the helicoil insert at first.
Then you can use a M12 screw to make the insert by your self.

You have to drill with a M12 threader a new thread in the head.
Diameter 12 is original inside the head for centering the bearing cap with
the bushing

If you are carefull, it works also with the head on the engine.
With good eyes and a sure hand

No Problem with this solution until today.-D


Good luck

Andreas

[ekranoplan]

1. Make sure your cam caps match the head - sometimes this is the reason for thread failure
2. Make sure your camshafts are all straight.
3. Check your valves in case they were bent by the experience.

All the best!

[gamma a.i.]

Bart, where is your reply...or do you have a splitting headache ? Johnny

[lancialulu]

Splitting head ache? Best with head off Bart.

By the way one of my failed inserts was a 12mm "repair" - maybe I had an old head of Andreas.

Anyway the alloy is sometimes so soft that it will fail in a larger area (maybe not immediately.) - I had this one welded up to sort.

Tim

[Bart Verbeek]

Hi all

Thanks for the advice and support. After some ours on the google-highway, the Wurth-answer on the Timesert story was giving me the best hopes. Untill I heard the price for the wanted kit. I just needed 1 (uno) kit not the entire factory. :S

Some telephones later, I found a guy who was familiar with the problem and was able to fix it. Price: the hours spend by the craftsmen. I'm not sure what it will be... later on this week (friday) I'll know the answer.... I sure think it's cheaper than the kit. And if one looses again now; it's WARRANTY. -D (or a slap against MY head for MY incompetence)

I was hoping to have the engine ready so I can put it in the berlina this weekend. Next week I wanted to invade 'la France' for holiday & some trailblazing for the sunday-route of the meeting. Not sure it will be with the zagato engine.... but it will be with the berlina which is serving as a shelf for zagatoparts and desk for the repair/concise/parts manuals for the zagato rebuild.... I think she will be happy when she's gone from her annoying sister who is getting slightly more attention for the moment. Girls & envyness.....

I'll keep you posted on the head-issues....

Bart

[racing]

nice joke tim

[tonykov]

A reminder that some of the the rocker shaft bolts are a different length and using the wrong bolt can result in a stripped helicoil

[Bart Verbeek]

Different lengths,..., hmmmm, I'm quiet certain the previous owner didn't knew that! B)

According to the variety on bolts he used.... the last owner was a owner of a British sportscar garage, he had the car for some time in maintenance, and later on, he bought the car from the customer. He loved the handling and the looks, but it was a forbidden love since he dealed in open british sportscars. So, I doubt he had seen such an unique advanced technique. He also hussled the bolts for the oilpan, some of them peeped into the engine! :X
I love this Italian complexity, I check all the bolts on it's lenght and mesure the holes.