I'm working on a rusty pig of a 2000 Chevy k2500 with a 6.5 diesel. The "bottom" pipe that connects the two manifolds together before the turbo rotted off, so I've got to replace it.
Shockingly, on the side that didn't rot off, the bolts came off after a discussion with Mr. Impact Gun. I was floored!
The other side, however, was a real pig. Everything there was rusted beyond recognition and I'm assuming that the nuts were carbonized directly onto whatever remained of the studs. I had to cut them off at the flange.
Luckily that gives me lots of stickout:
I'm assuming the studs are now part of the cast iron manifold, and trying to separate them will lead to more rust in my eyes and less of the stud sticking out.
How dumb is it to just weld new studs on to extend them? Will it actually hold up?
Note that this is one of those cone-connections, so there is no flange-to-flange sealing going on.
In reply to WonkoTheSane :
Are those not just pressed in from the backside? (I don't own any GMs)
thashane said:
In reply to WonkoTheSane :
Are those not just pressed in from the backside? (I don't own any GMs)
Unfortunately not. It would have been equal or less work for GM/Detroit to do that, but they didn't. They drilled and tapped the stud holes. They're blind.
I'd try lots and lots of heat on the manifold flange around the studs, to see if the metal will expand enough to break loose the rust bond.
My concern would be if you could get a good weld in there. There looks to be good metal, but the access looks less than ideal.
How much torque do they have to hold?
I should be able to tell you why from a welding tech standpoint, but all I have is a gut feeling that it's not a good plan. I guess if nothing else, your odds of getting the joint to excellent penetration and full diameter mean that you're likely to have a ready-made weak spot
I like the idea of heat, maybe some heat-wicked wax or similar, and a stud extractor.
And if that doesn't work, drilling them out.
How bad is removing the manifold, should it come to that? How expensive are replacements? (Looks like Rock Auto has them starting at $57...)
I think, if you have the skill to weld stud extensions to them, and keep all three straight, they would be plenty strong. But I could drill and tap the holes easier, if heat did not break the rust bond loose. I would not want to have to do any of those three options in place, so I don't envy you that! Pull the manifold if ya can, heat as first choice, if not.
I'd cut them flush and drill with good cobalt or titanium bits.
When I had a similar situation, I was able to use a MAPP gas torch to heat the broken studs up to dull red, and then turn them out with a vice grip. However, the holes weren't blind on the exhaust manifold I did it to, and I had the engine out of the car, so more room to work with.
If all else fails, I've seen people use small c clamps to hold exhaust flanges together. They seem to last way longer than they should.
Honsch
Reader
5/14/21 12:21 p.m.
How much time to you have?
If it has to be done today I'd weld on a nut, then apply heat to the flange to try to break the stud loose. If that fails, cut it flush then drill it out.
If you have time, welding on a nut then allowing days for penetrating oil to work can help. Try to work the stud to get it to wiggle a bit then add more penetrating oil. Patience works wonders. If alll of that fails it's back to cut flush and drill out.
I can't remember if it is Kroil or another brand of penetrating oil that we used on a 300k mile Michigan Duramax a couple years ago. It was here at the farm because I am the one with the torches and homeowners insurance. The penetrant supplied by my FILs friend, who owned the truck and I assume he stole it from the shop at the railroad where he and my FIL worked. We soaked the carp out of it for at least two days going back two or three times per day to reapply. On the morning of day three I hassled with getting the torches unburied and out to the drive along with a few extensions, a female bolt extractor that kinda fit and a 1/2 inch breaker. I figured I would give it a go and the damned thing nearly fell out on its own. I'm talking less torque than I would use on a light bulb.
Seriously look for the best chem angle first then heat if necessary before the weld ons with what you have.
To answer some questions in no particular order:
I'm a middling welder, and things I weld tend to stick together, but calling what I do welding is an insult to welders. It's mostly luck, gas, and a fairly powerful welder MIG.
Access is... well, it could be a lot worse. I could get a welding gun in there probably okay-ish.
If I take the manfold off, it will add at least 10-16 hours to the project, and then I'd have to deal with 8-12 stuck/broken studs instead of 3. That's also assuming the manifold survives disassembly. Honestly, that might be enough to scrap the truck over. I'm taking this one off the table for now.
Torque isn't crazy high, this is one of those cone-type connections that use the magic silver doughnut to squish, so it's not as bad a typical double-shear flat-flange type connection, but welding always weakens the metal around the connection, which was a big concern.
I did stop by Orielly's at lunchtime today, and I picked this up: 
So I'm going to try MAPP gas, and then strip the finest chinesium pot metal that Orielly has to offer.
Cutting it flush and drilling would be my last resort, there's one hole that doesn't have direct access unless I take the front driveshaft off, which is doable, but I don't need direct access for a welder, only side :)
Thanks everyone!
QuasiMofo (John Brown) said:
I can't remember if it is Kroil or another brand of penetrating oil that we used on a 300k mile Michigan Duramax a couple years ago. It was here at the farm because I am the one with the torches and homeowners insurance. The penetrant supplied by my FILs friend, who owned the truck and I assume he stole it from the shop at the railroad where he and my FIL worked. We soaked the carp out of it for at least two days going back two or three times per day to reapply. On the morning of day three I hassled with getting the torches unburied and out to the drive along with a few extensions, a female bolt extractor that kinda fit and a 1/2 inch breaker. I figured I would give it a go and the damned thing nearly fell out on its own. I'm talking less torque than I would use on a light bulb.
Seriously look for the best chem angle first then heat if necessary before the weld ons with what you have.
I dunno man, that kinda sounds like a fish story... "No, really, the stud came RIGHT OUT!" "I'm TELLIN YA!" :)
It seems to be the consensus to be optomistic about heat and various pulling equipment, so I'll give that a go. I have been soaking it in ATF/Acetone which is my libation of choice.
I'm more of a meat and taters guy but I understand the world and why you may think I'm casting a line. The other part of the story was that I did not start the repair but I got to finish it. Did the two old guys try to take it out righty tighty? Maybe. Did they just get tire of working under a Michigan rust bucket in 65° weather? Possible. All I can say is that I sprayed it again and again until I was ready to give it a shot and the stud came free. I am certain that your mileage may vary which was why I added the heat may be optional caveat.
QuasiMofo (John Brown) said:
I'm more of a meat and taters guy but I understand the world and why you may think I'm casting a line. The other part of the story was that I did not start the repair but I got to finish it. Did the two old guys try to take it out righty tighty? Maybe. Did they just get tire of working under a Michigan rust bucket in 65° weather? Possible. All I can say is that I sprayed it again and again until I was ready to give it a shot and the stud came free. I am certain that your mileage may vary which was why I added the heat may be optional caveat.
I was just joking, I've worked on rusty junk long enough to know that there's always one bolt/stud to give you hope right before your project difficulty and time estimate go crashing with all your hopes and dreams.
You just got lucky that the one you needed was the "the one." :)
In my case, it was the nuts on the other header. They spun "right" off (sure, they were smoking, but they came off!).
AAZCD (Forum Supporter) said:
I'd cut them flush and drill with good cobalt or titanium bits.
Blind holes are a bit more of a challenge. And upside down, in place, under a vehicle... no fun.
ATF/acitone is ok, but it won't have the "creep into the crevices" potential as Kroil. That stuff will work wonders! I became an early adopter of Kroil in the 80's from using it ind the Shipyard. I've gone back to preferring P B Blaster for most stuff, but a rusty exhaust stud, Kroil is head and shoulders above anything I know of.
Remember anything you soak it with WILL be VERY flammable, so be prepared. It IS gonna catch on fire!
Another help for soaking... apply. Let sit for a bit. Add some vibration, by generous application of mechanical persuasion (ie BFH). Let sit for a while. Apply again with more vibration (helps the creep into crevices action) Kroil is advertised as being able to creep upwards into a 1 millionth of an inch crevice.
eastsideTim said:
If all else fails, I've seen people use small c clamps to hold exhaust flanges together. They seem to last way longer than they should.
I just heard "weld disposable c-clamps in position after locating the flange with the studs," and honestly, I'm kinda liking my odds there...
03Panther said:
ATF/acitone is ok, but it won't have the "creep into the crevices" potential as Kroil. That stuff will work wonders! I became an early adopter of Kroil in the 80's from using it ind the Shipyard. I've gone back to preferring P B Blaster for most stuff, but a rusty exhaust stud, Kroil is head and shoulders above anything I know of.
Remember anything you soak it with WILL be VERY flammable, so be prepared. It IS gonna catch on fire!
Another help for soaking... apply. Let sit for a bit. Add some vibration, by generous application of mechanical persuasion (ie BFH). Let sit for a while. Apply again with more vibration (helps the creep into crevices action) Kroil is advertised as being able to creep upwards into a 1 millionth of an inch crevice.
Good to know. I'll see if the FLAPs have kroil on the shelf.
That's a textbook example of why I recommend that every shop have an oxy-acetylene torch. Heat the manifold ears red hot and those studs will come right out.
APEowner said:
That's a textbook example of why I recommend that every shop have an oxy-acetylene torch. Heat the manifold ears red hot and those studs will come right out.
Hmmm.. I Doooo have an O-A torch.. I'm always a bit scared to use it because it gets black "dust" everywhere that I'm assuming shortens my life by years for every minute I'm around it, and I stand about a 50/50 chance of liquefying my problems. Which does solve them. But it also creates new ones.
Looks like Kroil is available here:
Montville True Value Hardware 907 A NORWICH NEW LONDON TPK. UNCASVILLE, CT 06382-1917
Which is apparently THE farthest from where you are in CT
or at McMaster Carr.
Solvents will just give you false hope.
Get them manifold ears orange.
WonkoTheSane said:
eastsideTim said:
If all else fails, I've seen people use small c clamps to hold exhaust flanges together. They seem to last way longer than they should.
I just heard "weld disposable c-clamps in position after locating the flange with the studs," and honestly, I'm kinda liking my odds there...
If it's stupid, and it works, it's not stupid.
QuasiMofo (John Brown) said:
Looks like Kroil is available here:
Montville True Value Hardware 907 A NORWICH NEW LONDON TPK. UNCASVILLE, CT 06382-1917
Which is apparently THE farthest from where you are in CT
or at McMaster Carr.
Yeah, I stopped by all the stores in town with no dice. I'm going to try heat and Chinesium mixed with hope, then we'll see how it goes from there.
