Head replacement. Engine in or out?

scott123007

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Jul 27, 2012
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1,471
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Jupiter, Florida
I think a mountain is being made out of a mole hill. Just get some Permatex High Temperature thread sealant, put it on the stud, and call it a day. It's good to 400 degrees. If you don't feel that is enough, you can use some JB Weld extreme heat metallic paste. Put a dab on the tip of the stud and coat the threads with that and screw it in. Since you have a pin hole in there already, it should screw right in without causing a high pressure air pocket. Good to 1000 degrees :)
 
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andrew_donaldson1

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Feb 4, 2024
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Liverpool
Maybe you could make a Threaded Plug (about 5mm long), and insert it with a flat or Alem screwdriver and glue and then insert the stud (a little shorter now)……if you weakened the bottom of the hole (where the water comes out), You run the risk of breaking it even more when you adjust the stud...but if there is already a threaded plug on the bottom, the stud will stop on it...and you can adjust the stud to the corresponding tightening torque...(without a plug on the bottom , “maybe” the stud ends up breaking the hole even more when tightened
View attachment 108697
something like this

View attachment 108698
That's a good idea. A dab of JB weld on the end of the grub screw would also hold the weld in place to cure.
 

blitz11

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Sep 23, 2014
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314
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SW Montana
I bought some used BMW/5 heads off of ebay. Seller packed them like crap. Dented the hemi combustion chamber. Took my dremel tool, and then smoothed the head with a sanding wheel, then filled the "holes" with JB weld (really cleaned it up).

Reassembled, then ran it for a month. Pulled a head, and the JB weld was still there. The 600's detonated like crazy, but the jb weld held.

My daughter's KTM EXC had the a replated cylinder, and there was a small pin hole leak from the cooling channel into the exhaust port. Smoked white, and used coolant.

Made a pressure test rig, found the leak while the cylinder was submerged, and once dry, covered cooling channel with JB weld (not the qwik, but the standard).

She rode that bike 15 years without a bit of leakage.

You'll be fine if you do this.

1. put a bit of JB weld in the hole. Give it plenty of time to set up, and make sure that the new stud doesn't contact that JB weld.
2. Use red stud mount loctite on the threads to seal the threads and hold the stud (see post above). Don't use teflon tape - that stuff is slippery, which is what you DON'T want.

Reassemble with never-seize on the exposed threads. That way you won't have to back out the stud ever.

Ride the p!ss out of it.
 

andrew_donaldson1

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Joined
Feb 4, 2024
Messages
14
Location
Liverpool
I bought some used BMW/5 heads off of ebay. Seller packed them like crap. Dented the hemi combustion chamber. Took my dremel tool, and then smoothed the head with a sanding wheel, then filled the "holes" with JB weld (really cleaned it up).

Reassembled, then ran it for a month. Pulled a head, and the JB weld was still there. The 600's detonated like crazy, but the jb weld held.

My daughter's KTM EXC had the a replated cylinder, and there was a small pin hole leak from the cooling channel into the exhaust port. Smoked white, and used coolant.

Made a pressure test rig, found the leak while the cylinder was submerged, and once dry, covered cooling channel with JB weld (not the qwik, but the standard).

She rode that bike 15 years without a bit of leakage.

You'll be fine if you do this.

1. put a bit of JB weld in the hole. Give it plenty of time to set up, and make sure that the new stud doesn't contact that JB weld.
2. Use red stud mount loctite on the threads to seal the threads and hold the stud (see post above). Don't use teflon tape - that stuff is slippery, which is what you DON'T want.

Reassemble with never-seize on the exposed threads. That way you won't have to back out the stud ever.

Ride the p!ss out of it.
Great thanks. Can i ask why the new exhaust stud couldn't touch JB weld once its set?

Keen to torque the stud down to spec you see...
 

Tenforeplay

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Apr 29, 2023
Messages
253
Location
Kansas, USA
I wouldn't torque the stud, just insert it with the sealant. The only reason to torque the stud would be to keep it from backing out, that would have to be more than spec'd for the nut which is something like 20 lbs or nm. Using studs on engine blocks I've never torqued them, just insert with antiseize, use 80 lbs on the nuts and the studs never come out when the nuts are removed. But if your's does come out, just reinstall with sealant. KISS
 

andrew_donaldson1

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Feb 4, 2024
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Liverpool
Thanks for everyone's help. For continuity of the thread, here's what i did based on the above advice. After an overnight water test and a heat cycle today seems to have worked:-

Put a small amount of Jb well high heat on the flat end of a 7mm drill and pressed it into the bottom of the hole and padded it out.

I waiting for an hour and put a tiny additional layer on top using same method.

Then left overnight to test if it was water tight and it was. Great.

Then today i put a dollop of jb weld high temp gasket sealant into the bottom of the hole and also on the new stud thread and then inserted the stud to finger tight only.

Left for an hour, reconnected the exhaust and ran an engine cycle through and no leaks so far. Will monitor over coming weeks but seems like a fix thankfully saving me a few hundred quid.

Thanks everyone.
 
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