LSx Exhaust flanges / collector flanges

[BR3W CITY]

What are you guys using for exhaust flanges off of stock manifolds?
The tbss manifolds I have use a 3 bolt pattern, but its not a standard bolt circle. What are you guys using to connect your stock manifolds to the rest of the exhaust system?
My only thought is to track down a set of junkyard cats, and have them cut off the flanges and a stub of piping, and use that to start my exhaust from. I'd appreciate some suggestions.

[faribran]

i thought it was a bit strange.. but the guys on one of the Sunday TV shows just "whacked" off the original flange and welded on an extention of pipe(the manifolds are steel, not cast, so they said) for what its worth...

[BR3W CITY]

I've heard that mentioned as well, mainly from the turbo guys putting vbands on them. I'm plenty capably of welding exhaust piping, but welding that thick manifold steel is probably above my skill level, was hoping for a flange to start with.

[harnalien]

This is a big obstacle I'm trying to overcome as well. When I call around to yards, they don't seem to know what I'm talking about. I just ordered these from eBay http://cgi.ebay.com/ebaymotors/2-5-3...item3f0939549e. I haven't tried them yet but have my fingers crossed
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[BR3W CITY]

hmm. Those look like regular 3" bolt circle flanges, are you thinking you can elongate a hole to get it to work or something?

I'm going to see if they will cut me a "stub" off of the exhaust, I might be able to get the 02 bungs in there if im lucky. Do you know if the truck exhaust and the tbss exhaust pattern are different?

[harnalien]

I really don't know if there is a difference between the tbss and truck manifolds. I've got a bad feeling these flanges won't work, but I'm getting desperate. I may just have to have the exhaust shop make me some or start calling yards again.
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[TR65]

I used the stock pipes from the manifolds to the back of the cab. I have SSR exhaust manifolds, the same as Trailblazer SS I think. They used a regular exhaust biscuit on one side for a seal and a copper o-ring on the other side. Made a very solid connection. So using stubs off of a stock rig should make a good system.

Amazingly in my case the stock pipes, cats, and all perfectly fit in my C10. No modifications required. I just hooked up to the outlet flange at the back of the cab.

TR

[usmcchevy]

The passengers side flange is symmetrical, but the drivers side is a bit odd.
https://dragtimes.com/parts/LS1-Exha...641553675.html

I'm currently in need of a drivers side...

[harnalien]

So those in the link will work for sure?
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[85burb]

I went to every shop in town that did exhaust and none had a pattern or anything that would work. I went to a junk yard and took some off a motor they had on a shelf. They did not even know what i was talking about. It is just best to go walk the yards calling is mostly a waste of time around this area. Only gave 10 bucks for the set.

[usmcchevy]

Originally Posted by harnalien

So those in the link will work for sure?
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That is the pattern that the Van, trucks and TBSS use.....I don't have any car manifolds here to check them.


Problem that I see with cut flanges like that is, how do you seal them? Factory flanges have a grove for a seal, those don't.

[BR3W CITY]

u could use sheet copper and do a flat gasket

[usmcchevy]

Looks like GM used the same flanges on all of the trucks. Got one off of a 00 GMC 1500 with a 4.3 V6. Just laying on the ground next to the truck like it was ment to be mine $2

[BR3W CITY]

I found the flanges in raw steel (as priced) or avail. in stainless
from spd exhaust
F5172109 $36.70 each
F5162109 $33.25 each
Those are the part numbers for the drivers and passenger flanges. I haven't ordered them yet, as I have a junkyard trip coming this week, and I'm going to see if i can get them on the cheap.

[harnalien]

Would these work?

http://cgi.ebay.com/ebaymotors/Ls1-f...Q5fAccessories

[ls1nova71]

Originally Posted by harnalien

Would these work?

http://cgi.ebay.com/ebaymotors/Ls1-f...Q5fAccessories

Those will only work if you have F-body manifolds, won't fit truck manifolds.

But as a side note, they're not hard to make, provided you have a torch a drill and a die grinder. You can make just the flange, like the ones you put the link to, then go to a muffler shop and find a donut gasket that will fit in the end of the manifold, it doesn't have to fit tight, but it does help when installing them if they stay in by themself, then get some exhaust pipe a foot long or so, and have them flare the end to match the donut gasket you just got, slide the flange over the pipe and bolt it to the manifold with the donut gasket in between. This seems to work better than a flat gasket because it's not trying to bolt the whole exhaust pipe up flush with the manifold, it gives you some ''wiggle room'', then when you tighten them up you're good to go. This pipe is also a good place to put your O2 bungs in if you cant use the location in the manifolds. Muffler shops sell them pretty cheap.

[softballnrd27]

Just put a v-band flange on it and call it good. These manifolds weld very easy, just preheat and then let them cool in the oven.

[harnalien]

ok, last try before i hit the yards again. what about these?

http://cgi.ebay.com/ebaymotors/LS1-E...item4158a0fd88

[ls1nova71]

Originally Posted by harnalien

ok, last try before i hit the yards again. what about these?

http://cgi.ebay.com/ebaymotors/LS1-E...item4158a0fd88

Yes, those will work for truck manifolds. You are looking for truck flanges right? I just realized this thread is kind of generic, and when you posted the last link, I just assumed you were wanting truck manifold flanges.

[Clyde65]

Harnalien, I thought you had headers?

[harnalien]

Yes i'm working with the stock truck manifolds. I'd like to have headers, but the ones that are known to fit are way out of budget. there are some other cheaper headers that some say work, but I can't afford to take chances buying something that may or may not work. I would love to find the stock flanges with the pipe down to the o2 sensor, but my plan for now is to use those flanges and have an exhaust shop build off of those and mate to my existing exhaust.

[BR3W CITY]

hmm that ebay link ain't bad, about 1/2 the price of the spd ones I found. I'm hitting the yard tonighte, so if i strike out there, I may have to use those.

[67shortie]

If this will be of any help, the TBSS manifold I used worked with standard truck flanges that the exhaust shop had in a big box of stuff they had lying around. I guess I got a little lucky with that. they are different one is more triangle style and one is more unsymetrical like the 2 bottom holes are closer together like a skinny pyramid style.

They used 2 different style of gaskets one used a small donut style of gasket and the other used a rolled steel compressable ring. Doesn't leak, and the gaskets were only $9 for both.

[harnalien]

Well I broke down and bought some Schoenfeld headers. I read a few build threads on here and other sites and they should work. I figure they are priced nice and by the time I buy different flanges hoping they work then try and get an exhaust shop to piece something together, I've spent just about the same amount ad the headers of not more. I should have them on by the beginning of next week.
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[Clyde65]

Harnalien,

Please explain to your wife, I had nothing to do with that decision.