<VV> Helicoil Advice

tony.. tony.underwood at cox.net
Fri Jan 28 10:28:19 EST 2022

>> On Jan 27, 2022, at 11:48 PM, Todd Miller via VirtualVairs <virtualvairs at corvair.org <mailto:virtualvairs at corvair.org>> wrote:
>> Hi Folks:
>>   Looking for a little advice with helicoils, and to be honest, this isn't directly related to corvairs, other than I know many of you have had experience with having to use these with aluminum corvair engines.  The offending issue is on my son's 1986 Corvette with an L98.  We changed out the leaking water pump, and were concerned about the thermostat as well, so we attempted to remove the two bolts in the thermostat housing.  As these may not have been out since the car was built, both bolts sheared off.  One loosened a bit, and broke off when we tried to tighten it back up.  The other broke off trying to get the bolt out.   A friend tried to Mig weld a nut on the end of the broken bolts to try and remove them, but couldn't get enough penetration in to make it hold with any strength.   So, we are thinking that the only fix at this point is to try to drill out the steel bolts from the aluminum manifold and then put in a helicoil

You can bet the steel capscrews have bonded/jammed up to the dissimular 
aluminum via corrosion.    I have a C4 also, now I'm wondering if I'm 
gonna see the same issues if I have to replace a thermostat... odd 
considering such, seeing as how it's liquid cooled and 'Vairs don't ever 
need anything like that so it's been a very long time since I ever had 
to replace a thermostat.  :)

One thing you might try, from my dirt bike days with fasteners made of 
butter when they shoulda been made of guns:

Flat faced punch, wack the broken stud a bit with hopes the stud will 
"stretch" the aluminum threads slightly, opening up just enough space 
between the threads in the aluminum to allow the stud to loosen enough 
to come out.  Then maybe try a left-hand drill bit/stud remover kit 
(they sell them cheap, various sizes) or give the mig-weld nut another 
shot.  I'd exhaust all possibilities before trying to drill out the stud 
with the drill bit walking all over the stud doing its best to dig into 
the aluminum, and still the stud is likely to refuse to come out.

Another last ditch trick would be to heat the stud with a torch, just 
shy of melting the aluminum, the logic being to drive the O2 out of the 
"white rust" corrosion in the threads.   It might make the difference.  
MIG welding a nut to a broken stud does this as a part of the bargain 
which is the reason a nut welded onto the broken stud can take it out 
while the original head of the bolt would not.

Either way, BTDT, so good luck...

BTW I've always managed to remove any broken stud via any one or all of 
the above methods... it sometimes just wasn't very much fun.


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