heavy85 Posted January 20, 2005 Share Posted January 20, 2005 Well after porting my P79 head, too many hours polishing valves, valve job, two sets of seals (dont ask), misc other machine shop work I finally get around to assemling it back together and one of the #@$%'in cam tower bolts strip out when I try to pull torque. Turns out previous owner(s) had been in there before and poorly installed helicoils. Well the helicoils pulled out and now there is nothing left, sigh. So now what to do? I took it back to the machine shop (who had nothing to do with the helicoils) and asked their oppinion. They suggested trying a precision machine shop and seeing if they can plug the hole and remachine it. Since it locates the tower through the dowel pin it obviously has to be right on. It's the short bolt on the side that also had the head bolt going through the tower so I was pondering ..... would it really be that bad to just not use that bolt since the tower is located by the pin and held down by the cyl head bolt anyway? Can I JB weld the bottom of the hole and tap new threads into it so I dont disturb the pin bore at the top? What can I do? Thanks Cameron PS - one of these days I'm going to rant on all the things the PO's screwed up. Lets see, cam tower shims that were different thicknesses, mis-matched main bearing caps, various different jets in each carb (tripple mikuni), one jet not even screwed in because it was cross-threaded, twisted throttle shafts, stripped intake manifold bolts because they need to be studs, throttle that only opened about 1/2 way - and I'm just getting started on the engine let alone the rest of the car.....erg Quote Link to comment Share on other sites More sharing options...
SHO-Z Posted January 20, 2005 Share Posted January 20, 2005 Could you drill out both the head and the tower to a larger bolt size? Quote Link to comment Share on other sites More sharing options...
Pyro Posted January 20, 2005 Share Posted January 20, 2005 Common problem but not a big deal. Just install new threads (heli-coil). Buy some at NAPA or have a machine shop do it. Quote Link to comment Share on other sites More sharing options...
preith Posted January 20, 2005 Share Posted January 20, 2005 Common problem but not a big deal. Just install new threads (heli-coil). Buy some at NAPA or have a machine shop do it. I was going to reply the same thing, but in his post he mentions somone prior to him did a poor job installing the helicoils. I think the larger bolt might be the ticket, maybe that with a slightly larger helicoil? Quote Link to comment Share on other sites More sharing options...
heavy85 Posted January 20, 2005 Author Share Posted January 20, 2005 The helicoil is what stripped and there is not room to use a larger bolt without getting into the counterbore for the locating pin. If you screw with that counterbore then there is nothing to positively locate the tower on that side. Cameron Quote Link to comment Share on other sites More sharing options...
mjfawke Posted January 20, 2005 Share Posted January 20, 2005 As per the original question, I guess it would be O.K. as long as you leave the locating dowel in place, but I'd dummy up the head on the block and check the cam rotation to be sure. Quote Link to comment Share on other sites More sharing options...
olie05 Posted January 21, 2005 Share Posted January 21, 2005 If it was me I'd start with another head from the J/Y to not have to worry about having stuff torqued insufficiently... But you may not want to do that since you already have so much work into this head already. -Oliver Quote Link to comment Share on other sites More sharing options...
heavy85 Posted February 7, 2005 Author Share Posted February 7, 2005 I ended up using a 'thread repair kit'. Sort of like JB weld which you fill the hole with, put release agent on the bolt and set the bolt into the stuff, let sit for 5 minutes, remove bolt and you have fresh threads. Well I wasn't brave enough to trust this so I ran a tap through the stripped holes so there was a little roughness for the goop to stick to then just used the goop to glue a new helicoil in. Worked good. Cameron Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 7, 2005 Share Posted February 7, 2005 They do make oversized helicoils for such situations... I wouldn't trust epoxies in the head for long-term stregnth. I like metal-to-metal interlocking. If nothing else a Keen-Sert would have solved the problem, the next step if the "Helicoil Helicoil" gets pulled out somehow. You pull a keen-sert out, you need to have your head examined! The keen sert uses something like a 1/2-13 outer male thread for a 5/16-24 effective female thread! Quote Link to comment Share on other sites More sharing options...
tah Posted February 7, 2005 Share Posted February 7, 2005 If the threads are gone to the point of no return, why not have the opening filled by "brazing or welding" (whatever you want to call it!), machined and threaded? Whole lot cheaper than a new head. Quote Link to comment Share on other sites More sharing options...
510six Posted February 8, 2005 Share Posted February 8, 2005 See if the machine shop can install a Time Sert.I have had several stripped bolt holes repaired this way. http://www.timesert.com/ Quote Link to comment Share on other sites More sharing options...
Jolane Posted February 8, 2005 Share Posted February 8, 2005 I would also suggest a Keensert. Basically, pull the locating dowel out first, install the keensert, then replace the dowel. Joshua Quote Link to comment Share on other sites More sharing options...
heavy85 Posted February 8, 2005 Author Share Posted February 8, 2005 I would also suggest a Keensert. Basically' date=' pull the locating dowel out first, install the keensert, then replace the dowel.Joshua[/quote'] Not that it really matters but I couldn't have gone that route for the same reason I couldn't go with a bigger bolt because either method would have required drilling out the counterbore for the dowel which I obviously didn't want to do. Same reason welding it up wouldn't work. Cameron Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 8, 2005 Share Posted February 8, 2005 which is why the helicoil oversize would work.Basically they are sized for you to sink a tap down the already stripped hole directly, and thread in your coil, which restores the original thread on the interior area. Either way, the dowell would probably have to come out for the installation. Quote Link to comment Share on other sites More sharing options...
Jolane Posted February 8, 2005 Share Posted February 8, 2005 I am sorry, I did read that about drilling out the dowel hole. I was only thinking that you could plug the hole basically, and then redrill and retap for the dowel hole and bolt hole. Thought a keensert might get you close, so all you had to do was redrill for the dowel. Joshua Quote Link to comment Share on other sites More sharing options...
Kash Posted July 16, 2012 Share Posted July 16, 2012 Currently in the same boat, anyone know the size keensert/ timesert or helicoil kits that I will need to replace several of my stripped cam tower threads? thanks. Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 19, 2012 Share Posted July 19, 2012 Jeebus who's been working on these heads?!?!?!?! Put it on a shelf and get another from a JY while you still can. Later, the head can be machine repaired when there is no alternative. Quote Link to comment Share on other sites More sharing options...
BlueStag Posted July 20, 2012 Share Posted July 20, 2012 Jeebus who's been working on these heads?!?!?!?! Put it on a shelf and get another from a JY while you still can. Later, the head can be machine repaired when there is no alternative. He has a ton of recent word sunk into this one. Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 21, 2012 Share Posted July 21, 2012 I refuse to use Twitterisms like "@Kash" but it should be inferred my reply (since I replied above earlier) is in response to the newest response...which doesn't state that. Having work done on a linered head... OK, suit yourself... But proper machine shop would check / tap these holes and pay particular attention to any previously installed Helicoils. Stripping out a Helicoil is EXTREMELY difficult unless you MASSIVELY overtorque the fastener. Has nobody measured the tapped depth of the hole and seen if a 'deep Helicoil' can be installed in the threads deeper down the hole. On an M8 Helicoil, they are ONLY 8mm Deep. That's all you need for full grip strength. On bare aluminum threads maybe more than that, but assuming the standard Helicoil was installed, then reefed out, a slightly longer bolt, along with a Helicoil at the bottom of the existing hole would do the job. This is basic machine shop stuff. That the shop didn't know this is disappointing. Pulling a locating dowel and re-reaming halfway through a Keen Sert is not a big deal, and I can't see why the OP is so resistant to doing this. We're talking a $50 repair to a head which I have to assume has $2,400 in head work by the way it's played up. Seriously, if you got $350 into it for a valve job and a 'port cleanup' shelve it, get another, and save the head for when spending $50 for a repair on a Linered P79 makes economic sense. You got $2400 into the head, this repair is a no brainer. Does he have $2400 into the head? If not..... Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 21, 2012 Share Posted July 21, 2012 (edited) And I don't know what "Precision Machine Shop" means, as any guy with a Bridgeport Mill and Starrett Last Word indicator can do the setup on this repair after half a bottle of Jack Daniels and a weekend in Vegas... There are more than enough NC Shops in Illinois (well, maybe not Rantoul...) to do this work. A PHOTO should be worth a thousand words on this one... As I can't see how all this work was done and 'Poor Helicoils' went undetected until assembly! <div><br></div><div>Were I doing this in the back shed:</div><div><br></div><div>Measure pin bore.</div><div>Set up on pin bore centerline.</div><div>Drill / Ream for Keen Sert & Install.</div><div>Top Cut appropriately for bottom of Pin Bore</div><div>Bore Oversize for Locally-Fabricated Step-Pin</div><div>Install Step Pin</div><div>Reassemble...</div><div><br></div><div>Maybe more than an hour, forgot to take step-pin into consideration...but then again, making a SOLID over sized threaded-in Step-Pin to locate the tower is more involved (permanent, too, as the external threads on the lower portion of the step pin and inner threads for the bolt will NEVER come out or strip! But I digress...</div><div><br></div><div>This is all basic machine shop stuff. There is no 'specialty shop' required. Just a 'competent' one!<img src="http://forums.hybridz.org/public/style_emoticons/default/dry.gif" alt="<_<" class="bbc_emoticon"></div> Edited July 21, 2012 by Tony D Quote Link to comment Share on other sites More sharing options...
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