exhaust thread repair - M10 1.25 to M8

RatLabGuy

RatLabGuy

You look like a monkey and smell like one too
Joined
May 18, 2005
Location
Churchville, MD
On our 73 beetle, the exhaust studs are M8 1.25s. Some numskull PO drilled one out and re-tapped it for an M10, 1.25... which is the less-typical Jap-spec for M10 instead of the more common 1.5 thread pitch for European vehicles and what most bolts around here are.
I would just replace it with a step-down stud, but they are all M10 1.5 to M8 1.25. I'd love to find a proper M10 1.25 to M8 1.25 if anyone know of an application...

I tried a really thin heli-coil style adapter but they suck and it still wiggles a little bit. I suspect the case threads are a bit messed up.
Any other ideas?
The heads are cast AL alloy.
Is it feasible to TIG weld in AL into the hole, then re-tap it?
I'd have to rely on somebody w/ real weld skil;z rather than my hot boogers
 
Spend some of my tax doll hairs and buy a set of heads. They really aren’t that expensive compared to the butt pain you’re trying to overcome. See also. Fresh heads/vlaves/valve seals & seats XYZ…. Also, you’d know you’ve got a fresh matched set of heads in case you kind any other compression issues down the road. Not trying to spend your money but to me it’s pretty simple math.

Call apple tree or JBUGS and see what they say. Their tech is pretty on point.
 
skyhighZJ said:
Spend some of my tax doll hairs and buy a set of heads. They really aren’t that expensive compared to the butt pain you’re trying to overcome. See also. Fresh heads/vlaves/valve seals & seats XYZ…. Also, you’d know you’ve got a fresh matched set of heads in case you kind any other compression issues down the road. Not trying to spend your money but to me it’s pretty simple math.

Call apple tree or JBUGS and see what they say. Their tech is pretty on point.
Click to expand...
this might be the smart move, but the >$500 for a set of heads... when the prior ones seems to be working fine... is hard to justify when the whole point of this was to work through a relatively low-budget daughter/dad build project, knowing we're likely going to need to spend coin on something more modern as a daily anyway.
I only tore it down bc it was nasty and leaking.
Tom@Hilltop_Machine said:
Easy enough to make one if you want to go that route.
Click to expand...
thanks I will definitely keep that in mind, if I don't find another solution quickly I may hit you up.
 
You could apply some JB weld to those heli-coils, or...

www.ebay.com

4PCS M8x1.25 to M10x1.25 Reducing Screw 304 SS Exhaust Manifold Stud ATU | eBay

Adapter 1:M8x1.25. Adapter 2:M10x1.5. -This M10/M8 reduction screw is very easy to use, just screw it into the threaded connector or internal threaded pipe. 4x Exhaust Manifold Stud. -The product is made of 304 stainless steel material, with high hardness, good durability, good corrosion...
www.ebay.com
 
jeepinmatt said:
Buy an M10x1.25 bolt and drill the hole out in the exhaust. Done.
Click to expand...
That's what the PO did, but the exhaust manifold had some problems so I'm replacing it and the new one doesn't have a big enough lip around it.
And I'd rather have a more proper fix that won't cause future me to cuss at past me.... bc thats's happened enough already
 
OnlyOneDR said:
You could apply some JB weld to those heli-coils, or...

www.ebay.com

4PCS M8x1.25 to M10x1.25 Reducing Screw 304 SS Exhaust Manifold Stud ATU | eBay

Adapter 1:M8x1.25. Adapter 2:M10x1.5. -This M10/M8 reduction screw is very easy to use, just screw it into the threaded connector or internal threaded pipe. 4x Exhaust Manifold Stud. -The product is made of 304 stainless steel material, with high hardness, good durability, good corrosion...
www.ebay.com
Click to expand...
Nice find. But here's the thing...
from the pics
1773894088154.png

I suspect the title is wrong bc its some no-name drop-shipper of Chinese goods they don't know anything about.

Twice I have ordered something similar via Amazon and found that what came was mis-labeled and is actually M10 1.5. The above gives me little faith of not having the same thing happen again. In fact I'd wager this is the same thing I got previously.
 
The correct answer is to buy the 1.5 pitch stud, locktite the shit out of it, and jam it into the hole. It'll probably cut its own threads in AL.
 
mbalbritton said:
Is it that big of a deal to have one stud different? Just drop a 10/1.25 in and mark it/note it for future reference. Can’t imagine it’s something you’re going to constantly, if ever again remove. Hell, swap it for a bolt so you know it’s different.
Click to expand...
The exhaust flange is really close to the tube. There isn't enough room for the larger bolt head.
 
mbalbritton said:
But it’s large enough for a nut?
Click to expand...
An M8 nut, which is only 12mm. Or 13 if E-spec.
Your typical M10 is 17. J-spec is 14 but has a flange.

The old exhaust fits, new one doesn't.
This is a bug head that only has 2 studs on the flange, so its not like 1 can just be loose. I'd prefer it done right.
 
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