Hello everyone:
Not sure if I'm responding to the whole group or just James regarding
his head stud problem, but hope I can be of some assistance. I race a
1147 cc Spitfire in SCCA (G-PROD) and we tend to have head studs pull
from the block. There are several ways to improve this problem.
1. you can heli coil the block. once the threads are pulled out all you
need to do is clean the hole with the required drill bit and retap. the
hole will for the most part keep the tap straight but do keep a close
eye on it.
One thing to consider is that a course thread would be better in the
block than a fine thread as there is more meat to bite into the somewhat
poor casting ( though less threads ). You may also want to put as many
threads into the block as possible thus turning the stud over. This may
require you to put a sealant on the stud as you may break into the water
jacket.
2. you may also consider going upto a 7/16 stud. this also requires
retapping the block and makes fitting the head gasket difficult.
3. In the event a heli-coil fails you can go to a machine shop and have
them tap the block for a 5/8 to 3/4 plug and then drill and tap the plug
for the head stud.
4. When torqing the new head gasket I would recommend using a machine
shop nut. I use a fine thread nut with a built in shoulder that is used
on a mill table for holding down clamps. I think it takes a 11/16 wrench
you can also get the matching washers, This combination will never fail
and won't distort. Also use either a moly lube or cam lifter grease on
the nuts and washers. You may need to grind a little off the washer and
shoulder of the nut to fit them by the valve cover studs.
We torque to 55 ft-lbs and not had a problem since following no. 4 as
outlined above and have not had a problem in several years and we
replace head gaskets every other weekend.
Please feel free to ask any racing type questions and I will do my best
to let you know what at least we do on our car.
New to the group Chris C.
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