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Old 12-22-2016, 10:21 AM   #16
Mustachio
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Thanks for positive replies. Reweld it is then!
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Old 12-22-2016, 07:35 PM   #17
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Dont worry about the welds they will hold if you reweld it everything will move and they more than likely wont fit.

Just have the flange milled flat or if your careful use a big beltsander and just flaten it out and bolt them on
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Old 12-23-2016, 10:23 AM   #18
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I will definitely sand down the welds so I can see if they are as porous as I suspect. Also, the mating surface is only the bead of weld material so it's quite narrow, is that enough for a good seal? I will have to sand it down to make that smooth, and possibly reweld the connections on the other side as it's only tacked on, would that cause any warpage?
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Old 12-23-2016, 06:22 PM   #19
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I wouldn't touch them. I'd install as is and test them. If after testing you find leaks then reweld.
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Old 12-24-2016, 01:43 PM   #20
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Quit worrying and use a standard GM LS header gasket. They work just fine -- we've had one set on our car for 7yrs+ with no worries. I'm skeptical that no gasket is a good idea: expand-contract every heat cycle with steel headers expanding half as much as the aluminum heads. Yes, Sanderson says "no gasket, just HiTemp RTV", maybe that works but I trust that the GM Powertrain engineers know what they're doing.
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Old 12-24-2016, 03:30 PM   #21
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Appreciate the advice Garret, and thanks again for sending me the missing mount .

I just don't like re-doing things when it could've been done right in the first place, but anyways, we will see...
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Old 01-03-2017, 12:57 PM   #22
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Any updates on this?
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Old 01-06-2017, 08:35 PM   #23
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No and probably won't be for a little while. But I saw that your are looking into the headers yourself, it seems like Hooker is an option, pun intended. If you can get them for 300$ like you say then go for it since I'm sure the quality will be better.
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Old 01-06-2017, 10:26 PM   #24
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Wow, just wow. I'm rather surprised at your patience. Here's to making lemonade out of a sour situation.
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Old 01-07-2017, 08:12 PM   #25
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Originally Posted by Mustachio View Post
No and probably won't be for a little while. But I saw that your are looking into the headers yourself, it seems like Hooker is an option, pun intended. If you can get them for 300$ like you say then go for it since I'm sure the quality will be better.
hahaha I am trying to get some 5th gen manifolds for cheap and see how they fit. I wont start the swap until I graduate from college, but thats a little over a year from now.
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Old 01-09-2017, 12:45 AM   #26
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I can't speak to the quality of the welds but the flange which bolts to the head is suppose to look like that. Garagistic recommends using a bead of high temp Permatex but otherwise the headers are suppose to be "gasket less"
"Gasketless" is horseshit.

That is also one of the most horrifying designs for a sealing surface I've ever seen. Just because someone sits at a CAD workstation does not make that person an engineer.
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Old 01-09-2017, 12:25 PM   #27
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"Gasketless" is horseshit.

That is also one of the most horrifying designs for a sealing surface I've ever seen. Just because someone sits at a CAD workstation does not make that person an engineer.
Why is that a bad design for a sealing surface?

While I agree that adding silicone or Permatex is cheating and what I would still consider a gasket, industry standards allow for the use of Permatex and still call the assembly "gasketless."

Don't confuse design with execution.
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Old 01-15-2017, 12:08 AM   #28
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It's weld bead applied to a flange and then ground. The contact pressure on the rings and the globs next to the bolt holes is going to be very high. It will be bolted to aluminum, which creeps and relaxes at elevated temp and high stresses.

ETA: To which "industry standard" are you referring?

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Old 01-18-2017, 03:38 PM   #29
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Why is a high contact pressure bad? What does it being bolted to Aluminum have to do with anything? Headers that use gaskets are steel bolted to Aluminum with a thinner piece of steel sandwiched in between.

The exhaust has minimal pressure (if any) and a perfect surface, while ideal, isn't needed. Gasket less manifolds come factory on many vehicles and their surfaces don't look pretty either, but they work. The biggest issue with bolting steel to aluminum is the difference in expansion rates will cause the header bolts to back out. A backed out / loose bolt will cause a leak regardless of what material is used as a gasket. Cast manifolds are slightly less prone to this but it still occurs. Either way, this has nothing to do with whether or not there is a gasket between the surface. Higher contact pressure is good, better seal. Since the torque on the header bolts remains the same, the only way to achieve higher contact pressure is to reduce the area. Hence ground flat bead run around each of the openings. The globs around the bolt holes are there to support the flange and even the clamping force across the whole flange. Otherwise, the flange would warp around the bolt holes when tightened. <-- that would really cause all kinds of issues.

Perhaps "industry standard" was a poor choice of wording. "Common practice" might be better. There isn't an ASTM, ASME, ANSI, etc reference I can send you to (at least not that I am aware of). However, it is common for manufactures to not use a gasket and still recommend some form of sealant be used.
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Old 01-21-2017, 09:29 AM   #30
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Why is a high contact pressure bad? What does it being bolted to Aluminum have to do with anything? Headers that use gaskets are steel bolted to Aluminum with a thinner piece of steel sandwiched in between.
"Creep" as I mentioned above. Go look it up. Evidently my pithy explanation of the phenomenon wasn't sufficient.

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The exhaust has minimal pressure (if any) and a perfect surface, while ideal, isn't needed. Gasket less manifolds come factory on many vehicles and their surfaces don't look pretty either, but they work. The biggest issue with bolting steel to aluminum is the difference in expansion rates will cause the header bolts to back out. A backed out / loose bolt will cause a leak regardless of what material is used as a gasket. Cast manifolds are slightly less prone to this but it still occurs. Either way, this has nothing to do with whether or not there is a gasket between the surface. Higher contact pressure is good, better seal. Since the torque on the header bolts remains the same, the only way to achieve higher contact pressure is to reduce the area. Hence ground flat bead run around each of the openings. The globs around the bolt holes are there to support the flange and even the clamping force across the whole flange. Otherwise, the flange would warp around the bolt holes when tightened. <-- that would really cause all kinds of issues.

Perhaps "industry standard" was a poor choice of wording. "Common practice" might be better. There isn't an ASTM, ASME, ANSI, etc reference I can send you to (at least not that I am aware of). However, it is common for manufactures to not use a gasket and still recommend some form of sealant be used.
Name one OE application for "gasketless" exhaust manifolds.
Or whose manifold looks like the Sanderson example.
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