Light Aircraft Association

We were torquing up the newly refurbished cylinder heads on our D9 last night...and one of the studs pulled out of the crankcase.

Has anyone had experience fitting "case savers"? (e.g. http://www.machine7.com/section.php?xSe ... c8385d92d8) Is this a straightforward task? Any tips/advice gratefully received....

I'd be tempted to give Barry Smith a call.

He I'm sure would be able to tell you if using inserts is a good fix.

Nick - too late now but did you use thread lubricant on the studs. If so, for the torque applied, the studs would be overstressed. In addition, torque wrenches, even new ones, are notoriously innacurate, sometimes out by 25%.
For the pulled stud - is there sufficient "meat" for a thread insert (helicoil) to be installed.

Bill, good point -- I'm not sure: one of the other chaps was doing the nuts. I'll check... Thanks for the reminder.

Out of interest are your studs M8 or M10 and what torque did you apply?
I haven't pulled a stud out of the crankcase but I have broken one.

did the same some while back only because i believed a torque wrench .....
it was found to be 50 percent out the wrong way ....
case stud worked fine no issues

I wouldnt use a "Helicoil" insert. Contact VW Heritage, they have the factory replacement inserts as used by VW. Far more superior.

Thanks for all the advice. I spoke to Barry Smith and he was very much in favour of case saver inserts (rather than helicoils).

He did say that the Haynes manual torque figures are for 10mm studs, so are far too much for 8mm. (To quote him approximately "The Haynes manual has been responsible for buggering up a lot of engines!"). I think our studs are 10mm, but we hadn't checked this before embarking on the work.

Having spoken to Barry Smith you will now know that the torque for M10 studs is 23 ft/lbs and that for M8 is 18 ft/lbs.
If you're interested my own experience is described here with a couple of photos and my broken stud is now in the LAA 'Black museum'.
http://sbeaver.com/cgi-bin/fournier/cut ... thread=871

Not very long after learning this I was able to stop a Nipper pilot in the same hangar from going down the same route with his M8's.

I thought I could recount the outcome... We decided to attempt this task in situ. We acquired a 1/2UNF × 10mm case saver (or rather a set),a shiny new 29/64inch drill, and a 1/2 UNF taper tap. We plugged all the orifices we could see with rag and tissue, moistened with WD40 so debris would stick to it, plus another wad behind the hole being drilled out. Then one of our number manfully agreed to wield the drill (cordless), aligning it laterally using another stud as a reference; someone else supported the drill from underneath to maintain vertical alignment, and to monitor that direction of movement. A third pair of hands held a vacuum cleaner nozzle close to the hole... And taking it all nice and easy, that did the trick holewise! Tapping the thread seemed like a bit of an anticlimax, though a bit of a pain with all the other studs in the way. Again, nice and slowly, with constant monitoring of alignment when starting the tap seemed to work fine. Great relief all round that with the case saver in place the stud lined up nicely with the others.

Then it was a case of carefully removing all the wadding, cleaning it up, and bolting everything back together. Final checks. Lots of prop twirling to get the oil back through the system, then some serious swinging... after a few goes the engine backfired half-heartedly. Hmm, that shouldn't happen with a Leburg system. OK: who put the starboard lower plug leads back the wrong way!? With that fixed, the engine burst into life third swing; and sounded very good!

Thanks to everyone for their advice.