<VV> Fwd: Re/ Pulled head stud/block repair

[ScottyGrover at aol.com]

I did this trick to a crankcase that had been in an engine fire;when I  
torqued down the head studs (the repair was on the last stud in order) the 
Grade  8 insert came apart along the thread lines. I went to the next size 
larger  tap--twice--same thing.  I wound up buying a new crankcase.
 
 
Scotty from Hollyweird
 
 
  
____________________________________
 From: simpsonj at verizon.net
To: cityhawk at sprint.blackberry.net
CC:  virtualvairs at corvair.org
Sent: 4/24/2011 11:06:06 A.M. Pacific Daylight  Time
Subj: <VV> Re/ Pulled head stud/block repair


I had a similar problem with a pulled head stud.  The  problem with 
helicoils
is that the commonly available ones are short (not  the full length of the
threads in the block) and you need all the holding  power you can get.  You
can get longer helicoils, but if the hole has  been enlarged beyond the 
"step
up" size of the helicoil, you have three  approaches.

One is to replace the block.  But if it is in good  condition otherwise, I'd
try a repair.

There are two repair options  as others have pointed out.  One is to have
someone weld the hole up  and then redrill and retap the hole.  That would 
be
the most  "professional" route.  The other -- which I used -- was to make  
an
insert.  Tap new threads into the existing hole sized to fit a  larger bolt.
That is, find a bolt that can be threaded into new threads cut  into the
existing hole.  Center drill and tap the bolt to fit a new  head stud.  Cut
it to length to match the thickness of the crankcase  -- ideally it will be
flush with the outside of the crankcase when you're  done.  You'll insert 
the
bolt from the INSIDE of the crankcase; but  before you do, measure the
clearance between the crankshaft and the inside  of the crankcase.  You'll
almost certainly have to grind the top of  the bolt down to ensure there's
enough clearance.

As long as there's  enough of the hex head of the bolt left to give a wrench
something to hang  onto, you're fine.  Put a sealant of some kind -- I'd use
Locktite to  make it permanent -- and screw the bolt in and snug it down.   
It
doesn't have to be overly tight -- the remnants of the hex head will  keep 
it
from pulling through.  Once the Locktite is set, screw in the  new head stud
(again with some sealant).  I don't think that stud will  ever pull out
again!

Jim Simpson
Group  Corvair
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