In a message dated 07/17/2001 12:52:16 PM Eastern Daylight Time,
brian@uunet.ca writes:
<< First, you get an 11 stud head to copy and drill the
head. Note that the stud is actually a necked down bolt that has a 5/16"
NC thread rather than the 3/8" NC thread of the stud. The head is then
used to locate the new hole in the block, which is normally drilled down
into the water pump opening on Cooper S blocks. If you're drilling a non-S
block then you could choose not to drill through and thus eliminate a
potential water leakage issue. The bolt is torqued to 25 ft-lbs only, and
not over-torqued, as the block is not very strong in that area. If you
don't have a handy Cooper S head to copy, just get a 1275 head gasket -
they all have the 11th stud hole punched in them. I've done this mod once,
but never bothered after that, as I never seemed to have head gasket issues
in that area that I needed to solve as long as I was using uprated studs
for all the regular studs. >>
All you really need is the head gasket for a drilling guide. The real trick
is to get the head gasket in EXACTLY the right place by aligning the other
nine holes. Make a centerpunch mark EXACTLY in the center of the hole to be
drilled. It is best done on a drill press so that the stud will be absolutely
straight. The tap can be mounted in a drill press too, and rotated by hand to
make sure everything is straight.
The head itself is pretty easy but again, proper location and straightness
are important.
I don't know anyone who still uses the smaller bolt next to the thermostat
housing. Just put a regular stud there and keep it simple. You can get an
11-stud set from ARP.
It helps to drill the extra holes through the head a little oversize in case
you miss your centers a little. I wouldn't worry if you drill into the water
pump cavity. Just put a little sealer on that stud.
This is for a 1275. I don't think this can be done on a 1098.
Jack Woehrle
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