ATS 093 leaky slip joint repair

david85

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Okay, story time.

There's been some discussion on this for a while. Basically, the ATS 093 turbo kit is designed to be installed relatively easy around the engine and you can tell the designer put some though into this. Aftermarket installs would have been in frame, while appropriately optioned assembly line trucks for 1993 and 1994 would have been factory installed. There are slight differences between the aftermarket 093 kit and factory turbo IDI kit, but the parts in this discussion are identical.

Specifically, Items 4 and 5 in the attached diagram. The connection between the Y-pipe and the up pipe is a ball joint interference fit. This allows 6 degrees of motion to allow ideal alignment between the pipes and also for thermal cycling. Overall, the 093 kit is well designed and also lends itself to relatively easy upgrades with custom turbos.

The problem is this interference fit tends to wear out over time. Probably due to some combination of vibration, corrosion and thermal cycling. The older 088 use a nearly identical slip coupling and it seems to be holding up just fine on my truck, which still has the 088 kit. I'm not sure if it affects all such kits produced by ATS, or if there's something unique to the smaller Y-pipe on the 093 that makes it more vulnerable. I don't know what specific alloy the cast iron is, but I presume its weldable since some have been able to weld other castings in the kit (downpipe upgrades, for example). I'm counting on the weldable part.

The easy solutions to this have been tried by a few others:

1. Exhaust pipe cement
2. Hi Temp Silicone sealant
3. Steam pipe sealant (deacon)
4. Insert a thin metal shim to take up the clearance

As far as I can tell, they all work for a little while. I had high hopes on option 3. High enough that I actually ordered can of the Deacon product that ocnorb used on his thread: https://www.oilburners.net/threads/...-leak-has-killed-my-boost-2022-edition.91627/

But as some of you already know, it still ended up failing.

The solution I'm going to attempt is probably the most expensive but I also feel is most likely to work. Basically, this will be similar to a knee or hip replacement surgery:

1. Cut off the worn out parts
2. Install a replacement connection that is machined to original tolerance.

Here's what I've done so far.

1. Take careful measurements of the original parts.
2. Design a 3D model in AutoCAD of what the parts should be (to the best of my ability).
3. Take that model to the local machine shop and have them make new ones out of 304 stainless steel.

See attached for what I have right now. I asked for 0.001" - 0.002" interference fit. Some quick measurements look good but there seems to be a slight taper in the inside bore of the cylinder side. I could probably use this to my advantage though.
 

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IDIBRONCO

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Definitely keep us updated. If this is successful, I'll bet that there would be enough of a demand for this that the price may drop somewhat.
 

david85

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Definitely keep us updated. If this is successful, I'll bet that there would be enough of a demand for this that the price may drop somewhat.
I presume the machine shop would be open to a bulk production run but I'll see how this works before I broach the subject with them. They generally work on bigger items for MUCH bigger customers.

Welding is done. I made two welding passes with stainless steel filler rod. Then I heated each repair with a torch to hopefully anneal the welded zone. Some distortion already happened on the female side but we'll see how it all turns out once its cooled off. Even if it's slightly out of round, the thinner wall is flexible enough to still allow the two parts to conform.

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Nero

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Looks beautiful, always appreciate a good weld.
 

david85

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Looks like it works. The female side is slightly out of round so I used a vise to help assemble (by squishing it back into round). It might be worth making that part out of thicker material next time to prevent distortion. I'll have to see if there's enough room at the firewall.

The fit itself is really nice with good and tight interference. The assembly even rings as one piece when tapped with a metal tool. Now I have to go through the rest of the turbo kit to see what else I need. But this was the biggest hurdle right here.


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Nero

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ive been making these for about 4 years or so now.
Do you have any issues with the bellows cracking? Looks like the collector is also modified? Is it something that can be installed in chassis? I'm interested in one too....
 

david85

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ive been making these for about 4 years or so now.
That's probably a better solution if it still fits in a stock truck. Easier to take apart too.

Only thing that might happen is the turbo won't be held as rigidly to the engine. Maybe vibration could cause cracking of the pedestal over time? 4 years should be more than enough time to know if that's likely to happen though. Nice piece.
 

IDIoit

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That's probably a better solution if it still fits in a stock truck. Easier to take apart too.

Only thing that might happen is the turbo won't be held as rigidly to the engine. Maybe vibration could cause cracking of the pedestal over time? 4 years should be more than enough time to know if that's likely to happen though. Nice piece.
Do you have any issues with the bellows cracking? Looks like the collector is also modified? Is it something that can be installed in chassis? I'm interested in one too....
fits a factory truck, with the firewall to floor pinch weld deleted.
this is with a 3" down pipe.
i havnt had one come back as cracked, the only issue ive had was a non factory turbo application, where the customer was running something different.

ive had one on my truck for 6 years and zero issues.
 

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david85

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I already deleted that floor seam when I did the cab restoration so it should fit. Looks like that'll be my next option if this doesn't work.
 

ISPKI

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With regards to the 304 stainless option - was that chosen for it's weldability or for low material cost (or both?). 304 doesnt handle high heat and friction well and I would be concerned that the vibrations and pivoting in that joint would cause it to wear out and fail. How long it would last is anybody's guess though. Looks like the cast iron welded great. I am also curious as to what filler wire you used for it, 309? 308? 312? Either way, those are some darn good welds on old cast iron.

I am trying to fix a cracked exhaust manifold from a 50s MG that had been brazed and it is proving to be an absolute bear. The moment I start to wet it together, it just blows up into the torch and craters out the manifold wall. Using NI-99 and NI-55 rods and they dont even wet into the iron, just ball up and float on the surface.

I use alot of those stainless steel bellows pipes at work - Helium spectrometer testing electron beam chambers. The ones we use are not cheap, coming in around 400$ per foot for a 3" diameter tube. I am guessing you're not using these however since these are high vac rated.
 

david85

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I used 316L welding rod, simply because that's what I had laying around. As for why I used 304, that's what I always used for other exhaust parts and it held up well. I doubt it would have cost much less if I asked for mild steel since most of the cost is usually shop time. Stainless does have a tendency to gall when subjected to abrasion but I figured it should still hold up better than cast iron. In theory, even mild steel should have worked here.
 
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