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Looks like you've drilled into the water jacket and one of the inlet manifold orifices on the block. As far as I can remember the order from the front is exhaust, inlet, inlet, exhaust, exhaust, inlet, inlet, exhaust. The guilty stud would seem to be the second one in. To prove this, you could block/fill it with some form of high temperature 2-pack epoxy such as J-B Weld (after drying, de-greasing and cleaning it out) let glue dry and reassemble without that stud in. If it doesn't leak QED but obviously you've got some serious thinking to do re. a permanent solution. Bodges like this would probably 'get you (a short distance) home'. Other way is to fill/loctite 1/4 - 1/2 thread with a flat screw head and rest with shorter stud thread but depend on quality of thread but will be much weaker. Permanent and more expensive solution will be replacement block.
Location: Ferring, Worthing, West Sussex
I always have believed that the manifold studs go through into the water jacket. A major contributor to the studs seizing and then shearing off when being undone. The same applies to head studs.
Yes, the studs go into the water jacket, and you have to hope the thread seals the hole....or it goes too far and blocks the small middle water passage - see an earlier topic about a week ago.
But is sounds like this stud has been drilled too far an water is coming out of the back of the hole directly into the inlet port, down the manifold, and out of the carb.
I think I would make a stud with a threaded portion long enough to go into the port, loctite it in, file the end off, add Radweld when refilling with water, and keep my fingers crossed.
Location: On a hill in Wiltshire
Thanks for the helpful comments.
This is adding up, as the leaking no.2 stud I originally removed was not a standard stud, but some threaded bar, going in quite a long way.
I only sent my drill in a short way before re-tapping, but
I think I may have disturbed an earlier repair of a hole in the waterjacket, because I didn't recognize the signs.
Someone else advised attempting a repair, so think I will have a go- not much to lose...
Will post an outcome.
I suggest removing the manifold and adding water to prove conclusively where the water is getting into the inlet port. It can't be the centre stud as that is between Nos 2 & 3 exhaust ports.
The implication is that the threaded bar you removed went through into the water jacket (As it should) but then further on and through the wall of the inlet port. If that is the case you should be able to feel the hole with a finger in the port.
It seems to me that the problem comes from removing the threaded bar which has opened the hole in the port. In all probability your repair to the manifold stud is done correctly but it doesn't seal the hole left in the port.
Manifold studs only have sufficient thread to do the job and so couldn't reach into the port.
If you take out the new stud you'll be able to tell if the old threaded bar went in a great deal further than the new stud. Also you'll be able to tell if it protrudes into the port as it should be possible to feel it in the port.
If this is the case then you might well be able to use a short length of the threaded bar you took out to screw into the hole in the port. As it apparently sealed before it might well do so again.