torque/thread specialists? stripped threads

raroz28

raroz28

Forum Member
I know we got a lot of creative dudes in this club and I'm in a pinch.

A bolt stripped out on the back of my cylinder head and it is a bolt that seals oil. I ran in a larger diameter bolt. It's an m6 originally, and I wrenched in a 1/4-20. It worked fine but I had to take it back out and it when I did it wouldn't hold torque again.

I think what I'm planning on doing now is using a stud instead. If I can get the stud in to grab a couple of threads, will the torque transfer from the threads in the head and spread throughout the stud and potentially hold? I'm kind of out of options here, as I cannot drill it to tap it without pulling the cylinder head.

Any suggestions?
 
What kind of head/car? Can you get a short bit and 90* driver then tap with a small wrench?

It might work with the stud, you can possibly jb weld or loctite it in place.
 
Well, M6 and 1/4 bolts are relatively the same size. The M6 is equiv to a fine thread and I am sure the 1/4" bolt you used was a course thread. The 1/4" bolt is just a few thousands larger and that is why it held for an instant. It would never have held for any amount of time. If you want to go up one size larger, then you need to go with either an M8 or 5/16 bolt. Otherwise, you'll need to Heli-coil it.

grr
 
mustangmike6996 said:
What kind of head/car? Can you get a short bit and 90* driver then tap with a small wrench?

It might work with the stud, you can possibly jb weld or loctite it in place.
Click to expand...

It's a B8 Audi A4 with the 2.0T. It's the vacuum pump on the back of the head. Only issue I see with using permanent loctite is if it ever has to come off. The way it's designed, you have to pull the unit with the bolt still inside of it. The bolt cannot be pulled out of the pump, as it hits the firewall and cannot be removed by itself. If I loctite the stud in, it will never come back out and the pump will be stuck to the head.

I was able to run a 5/16 tap in with my 1/4" ratchet, but the tap that came with the helicoil kit I bought (5/16-20) will not fit - it's too big and will need to be drilled.

I'm stumped.
 
Can you cut the tap down?

I mean, at this point there aren't too many options. Cut the new tap, taper the edge and run a die or thread chaser over the modified tap. Then run it in the head the way you did with the initial tap.
 
Make a key headed stud into a "self tapper". wedge the stud with a couple of nuts for easier install, especially for the amount of resistance it'll give back. Go slow and do not wiggle side to side any allowing for that stud to cut its own thread pattern into the head. Also, consider using a metal epoxy/weld compound to cement the stud permanently in place.
 
Beigg said:
Make a key headed stud into a "self tapper". wedge the stud with a couple of nuts for easier install, especially for the amount of resistance it'll give back. Go slow and do not wiggle side to side any allowing for that stud to cut its own thread pattern into the head. Also, consider using a metal epoxy/weld compound to cement the stud permanently in place.
Click to expand...

any idea of somewhere local that will sell a 4" stud like that? 5/16 or an m8 is what I think I'll go with.
 
raroz28 said:
any idea of somewhere local that will sell a 4" stud like that? 5/16 or an m8 is what I think I'll go with.
Click to expand...

I just got some 60mm stainless allen head M8 studs from McMaster Carr......couldn't find any locally. If you don't need the allen head, places like Ace carry them.

--Joe
 
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I would shove another stud in there with red rtv, maybe some Teflon tape also.. It wont be permanent but it will have a good bit of retention. Goodluck! I have had a week full of redneck engineering. ..haha
 
Does the bolt hold the vacuum pump? Does it have to hold anything? If not and you have the material in the head tap it 1/16 pipe. Pipe threads with sealer will seal the oil (is the oil under pressure?) If you must use a bolt, use small copper washers on both sides of whatever it is your holding and loctite.
 
So I got it finally. I ended up purchasing an angle drill from harbor freight that actually fit. I then bought a set of titanium bits from there for $15 and it included the 21/64 I needed for the tap.

Here is the space:
17862544_775054753993_8128438973387919725_n.jpg


I took the bit and broke it with a hammer to get it down to like 3 inches and it fit. I was able to drill and tap the hole for a solid fix. Thanks for the tips motown.
17903962_775054768963_9114228463747660568_n.jpg
 
Great that you didn't go the 'get by' option. Other potential future mechanics will appreciate it.
 
Beigg said:
Great that you didn't go the 'get by' option. Other potential future mechanics will appreciate it.
Click to expand...

I never thought I'd be able to make something like this fit back there.

I mean honestly there was no way to get around fixing that thread. I was going to pull the head if this didn't work.
 
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