elbekko Posted April 3, 2011 Share Posted April 3, 2011 Looks like the thread of the centre stud of the rocker shaft has stripped... probably got damage while transporting the cylinder head (or while they were skimming it). Tried copious amounts of strong loctite, but that let go as soon as I drove it a few metres. I've looked into Helicoils, but it seems to me they're better suited for through holes, as the little tab at the bottom has to be removed. And I don't fancy having to drill and tap an oversize hole in the head. And the damn thing has to be straight too. Any brilliant ideas on how to fix this? We've considered trying some 2-component metal glue, but I'm a bit hesitant to use that too... Quote Link to comment Share on other sites More sharing options...
rtbarton Posted April 3, 2011 Share Posted April 3, 2011 I've used Helicoils to line blind holes for head studs in a cyl;inder block without any problems. You use the same tool to wind the Helicoil in and to break off the tang. You have to take great care when you drill the oversize hole not to get the stud at a slope. Quote Link to comment Share on other sites More sharing options...
bishbosh Posted April 3, 2011 Share Posted April 3, 2011 Yep, helicoil is the way forwards. Quote Link to comment Share on other sites More sharing options...
NegevLandRover Posted April 3, 2011 Share Posted April 3, 2011 Yep, helicoil is the way forwards. Both my 300 TDIs are running helicoils in the middle of the cylinder head - don't know why it is always that one that lets go but it is. Brilliant invention that bit of kit - helicoil that is. Quote Link to comment Share on other sites More sharing options...
elbekko Posted April 3, 2011 Author Share Posted April 3, 2011 You have to take great care when you drill the oversize hole not to get the stud at a slope. Yeah, that's one of the things I'm least looking forward to... maybe I need to make (or get) some kind of jig for the drill so I can drill straight down. Also, what price range am I looking at for this helicoil tool? Quote Link to comment Share on other sites More sharing options...
rtbarton Posted April 3, 2011 Share Posted April 3, 2011 A Google should find you suppliers and prices. Also try Googling "Thread Repair Kit" as I'm sure there is a competitor to Helicoil, but I can't recall the name. Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted April 3, 2011 Share Posted April 3, 2011 I did a couple on my last 90, helicoil is the way :-) if it is not perfectly straight then tweak the stud with a bit of tube until it sits on the middle of the hole in the shaft. on my 300 the middle stud was fine but the front and rear had sheared the thread. I put it down to the strain of 2 timing belt failures. HTH Mo Quote Link to comment Share on other sites More sharing options...
mmgemini Posted April 3, 2011 Share Posted April 3, 2011 Machine shop. Drill out threads and tap a new one. Then have studs turned to suit the new thread insert and the rocker shaft stud. Quote Link to comment Share on other sites More sharing options...
Landy'd Gentry Posted April 3, 2011 Share Posted April 3, 2011 I have to say Helicoil or "Thread repair kit". I had a shot bolt in the middle of the rocker shaft, so, as stated above, drilled out old bolt, and then used a helicoil to reassemble. Job done! Quote Link to comment Share on other sites More sharing options...
Richy B Posted April 3, 2011 Share Posted April 3, 2011 Wurth do a product called "time serts" similar ( ish) to a helicoil but is a one piece item unlike a helicoil that is kinda a spring set up, Very strong, Many motorsport castings have them fitted as std, Your local engine shop should be able to help you out in this area Quote Link to comment Share on other sites More sharing options...
Les Henson Posted April 3, 2011 Share Posted April 3, 2011 KH Engineering in Swindon did the last one for me - £40 for cash and an excellent job Les. Quote Link to comment Share on other sites More sharing options...
elbekko Posted April 3, 2011 Author Share Posted April 3, 2011 Thing is, I'm NOT taking off the cylinder head again. I'd rather burn the damn thing to a smoldering heap of ashes. So taking it to a machine shop is a bit of a no-no. I'll try to get a hold of a helicoil kit... Quote Link to comment Share on other sites More sharing options...
mmgemini Posted April 3, 2011 Share Posted April 3, 2011 Why take the head off. You omly need tap the new thread. The maching shop makes the stud. Quote Link to comment Share on other sites More sharing options...
Range Rover Blues Posted April 3, 2011 Share Posted April 3, 2011 If you are worried there are companies that will comep out and do the helicoiling for you, my mate mentioned it before (when he used to work somewhere else than he does now, or I'd ask who it was). They did a lot of classic cars so a spare head or block was not always an option. Helicoils are brilliant, the fact that they aree a spring is part of their success, once wound in they are already an interferance fit. When I used to buy cast ali moulding tools I specced helicoils for the mounting points and important inserts because they were so durable, unlike a thread into ali Quote Link to comment Share on other sites More sharing options...
elbekko Posted April 3, 2011 Author Share Posted April 3, 2011 Thanks for wanting to suggest companies that do it, but I don't think trailering it across the channel for a bit of drilling is a good idea I'm up for doing it myself (or have a friend with more steady hands do it, I shake an awful lot for being 21 ), I'm just a bit worried about drilling straight. Quote Link to comment Share on other sites More sharing options...
v8bertha Posted April 4, 2011 Share Posted April 4, 2011 (edited) Could you not leave the pedestal and rocker shaft in place, just remove the bolt and then use that as a guide for the drilling? We did it to a friends 90 while on holiday in France a few years back. Just go at it with a certain amount of caution, make sure you catch all the swarf, and all will be fine. There is another type of thread repair kit thingy, an alternative to helicoils, but for the life of me I can't remember what they are called These was post not so long ago that mentioned it. Found it! http://www.timesert.com/ Edited April 4, 2011 by v8bertha Quote Link to comment Share on other sites More sharing options...
GBMUD Posted April 4, 2011 Share Posted April 4, 2011 Don't worry too much about drilling perfectly straight. Get a friend to help, you hold the drill while he stands back to look at the drill and tell you if you need to adjust the angle any. If you are really anal then you can buy pistol drills with spirit levels built into the body. It is quite easy really. 'Proper' machined aluminium parts are very often manufactured with thread inserts fitted from new. This is because aluminium is not really strong enough to take much stress on cut threads and will often strip during disassembly. Of course, motor manufacturers like to save money wherever possible... Chris Quote Link to comment Share on other sites More sharing options...
rtbarton Posted April 4, 2011 Share Posted April 4, 2011 ........Get a friend to help, you hold the drill while he stands back to look at the drill and tell you if you need to adjust the angle any. ...... Chris You need two friends at right angles, or maybe one cross-eyed friend Quote Link to comment Share on other sites More sharing options...
elbekko Posted April 4, 2011 Author Share Posted April 4, 2011 Could you not leave the pedestal and rocker shaft in place, just remove the bolt and then use that as a guide for the drilling? Probably, but I don't fancy drilling out the rocker shaft too, and you need an oversize hole for helicoil, right? Was wanting to order a kit, but I'm doubting between two now: http://www.amazon.co.uk/Silverline-1-25mm-Thread-Repair-Kit/dp/B001C7M4DG/ref=sr_1_1?ie=UTF8&s=diy&qid=1301933944&sr=8-1 or http://www.amazon.co.uk/Draper-Expert-44067-Heli-Coil-Thread/dp/B0034BCOTW/ref=sr_1_2?ie=UTF8&s=diy&qid=1301933944&sr=8-2 The price difference is pretty much negligible, but the Silverline kit seems to be more complete. Which one do you think would be best? Quote Link to comment Share on other sites More sharing options...
rtbarton Posted April 4, 2011 Share Posted April 4, 2011 Given reputations I'd go for the Draper. It's strange that they use the name "Helicoil" I thought this was a registered tradename, perhaps Draper have bought it? Quote Link to comment Share on other sites More sharing options...
elbekko Posted April 4, 2011 Author Share Posted April 4, 2011 Draper it is. Thanks for the help guys, if I feel like it I may do a write-up for the tech archive. Edit: ... or not. Draper doesn't ship outside of the UK apparently Guess I'll just go by a few stores tomorrow, and see if I can find it. Quote Link to comment Share on other sites More sharing options...
Range Rover Blues Posted April 4, 2011 Share Posted April 4, 2011 If you have a drillstand for you electric drill you can (with a bot of modification) assemble it with the drill on the opposite side to the baseplate. Clamp the baseplate to the flat surface of the gasket face and it will drill a "vertical" hole. Quote Link to comment Share on other sites More sharing options...
GBMUD Posted April 4, 2011 Share Posted April 4, 2011 <br />You need two friends at right angles, or maybe one cross-eyed friend  <img src='http://forums.lr4x4.com/public/style_emoticons/default/blink.gif' class='bbc_emoticon' alt='' /><br /><br /><br /><br />One portable friend should prove ample! Chris Quote Link to comment Share on other sites More sharing options...
Phil Hancock Posted April 4, 2011 Share Posted April 4, 2011 The rocker pedistal will work fine as a jig and the size you open out the hole to for rethreading is the original bolt size usually. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted April 4, 2011 Share Posted April 4, 2011 The rocker pedistal will work fine as a jig and the size you open out the hole to for rethreading is the original bolt size usually. I thought it was the original plus the size of the insert, so that the hole in the middle of the insert is the same as the original hole. Quote Link to comment Share on other sites More sharing options...
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