Here is another way to approach the problem. This comes from a very talented hobbyist for whom I have great respect. The threads stripped when the engine was completely together, and he was on the final round of torquing. This solution has been in place for more than three months.

The short story is that I made a hardened stud from a 10mm bolt and
epoxied it into the block.

I found a total of 38 mm of hole in the block. 11mm at the bottom
still had threads and 27 mm apparently was stripped out allowing a
bolt to slip in to the point of the remaining threads at the bottom.

With the cam and towers out of the way I was able to use a long 10mm
bolt with flutes cut in it to chase the remaining threads.

I ended up making three different studs from bolts. I used vinyl
tape to create a dam/squeegee at the top of the lower thread portion
of the stud. I did not want epoxy in the head hole and thought this
would help prevent that. I also put a single layer of vinyl tape on
the portion of the stud that would be in the head. I did not want a
bond with any stray epoxy between the stud and the head as I assumed
it would give me a false torque reading.

I raised the temperature of the workspace to 65 degrees and directed
a heat gun on the outside of the block closest to the hole assuming
this would improve the set up of the epoxy.

I used a funnel with a small hose extension to get lacquer thinner
into the bottom of the hole. I did not want to saturate the head
gasket around the bolt hole with lacquer thinner. I used an air
nozzle with an extension to blow oil and debris out of the hole. I
repeated this twice.

I mixed up a sample of JB Weld epoxy and applied it to one of the
extra studs I had made to see what its consistency was going to be
and watch its behavior on the threaded portion.

I applied epoxy to the stud that I had taped up. I made my best
guess on how much to apply. I did not apply any epoxy to the bottom
10mm of the stud. I had cut a slot in the top end of the stud to be
able to screw it in. I did my best to keep it off of the sides of
the hole in the head. I screwed it in with a screwdriver.

I put a nut on the stud and preloaded the assembly with 20ftlbs of
torque. I was confident the threads at the bottom would carry that
and I wanted the preload to give me a good final alignment while it
was setting up.

I directed the heat gun on the block for several hours to raise the
temperature and perhaps increase the flow of the epoxy.

Sixteen hours later I removed the nut and replaced it with a hardened
one. I had the "practice" stud that I had used to monitor the cure
of the epoxy. I torqued it down to 42ftlbs. It appears to be rock solid.

I am currently replacing the cam and towers and will proceed with the
final assembly as time permits.

If the stud holds I think a lot of credit can be given to the 11mm of
threads that were available at the bottom of the hole. They gave me
a foundation to work off of.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe