Well, using blue (medium) loctite and letting it dry overnight didn't help.
heliocoil still just works it's way out of the hole.
thanks to everyone for lots of ideas on fixing this. again these holes have
been heliocoil-ed before, so every time i drill and tap them the helocoils
just get looser.
So, below I've listed my possible options at this point, and I'll call my
machine shop tomorrow for their advice. But wait! You say you're dismayed
that your vote on Tuesday is just a vote for the lesser of two evils? Well
cheer up! You're vote below for one option from Plan A and one option from
Plan B will definitely make a difference to this Triumph owner in Carolina!
Vote today, and vote often!
Plan A: The top holes are open on the back, so three possibilities:
A1. I probably could put studs on the top holes with nuts on the backside.
I've still got plenty of aluminum head material around the holes, but i'm
slightly concered that the 3/8 stud will wobble around in the hole which is
now large enough to take a 7/16 bolt (and no, that bolt won't hold either)
so, maybe insert a bushing in the hole, and use flat washers to distribute
the pressure?
A2: If I try the heliocoil again, is there a millimeter bolt size that is
slighter larger than 3/8", but not as large as 7/6" which is the next English
size up and won't fit? Maybe a slightly larger millimeter bolt would keep
the heliocoil in place.
A3. Try using red loctite, which is the permanent stuff, although heat may
be a problem. I also thought about J&B weld, so I'll probably check out the
Internet tonight for other options for holding in the heliocoils.
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Plan B: The lower holes are blind, so studs with nuts on the end aren't an
option.
B1. I did heliocoil one of those holes, and it seems to be holding, so try
heliocoil on the other two with red loctite? Maybe heliocoil works better on
a blind hole for some reason?
B2. Try the other products similar to heliocoil that are solid inserts?
B3. Try the millimeter bolt trick mentioned above.
B4. Tap out to whatever is after 7/16.
Bruce
1980 Inca Yellow TR7 5-speed convertible
Chapel Hill, NC
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