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Building a turbo header, have questions


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I'm building a 304L stainless turbo header for my 83 280zx turbo. Should all the flanges at the head be connected? Also should I fit the pipes inside the flanges or can the just be butted up to the flanges? I've watched all the header building videos from stainlessheaders.com and was left with these questions. Thanks.

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You can cut the flange after it's built. It might (will) warp a bit after heat cycling though. This helps keep thermal expansion from breaking studs. Be sure to drill out the stud holes a bit more to allow for it as well. Corky Bell's Maximum Boost has a whole chapter or two about all this.

 

Are you using butt weld pipe connectors, or thin gauge tube?

 

I fit my pipe into my flanges. IIRC, my exhaust outlets were like 1.3" or something, I used 1-1/4" SCH10 pipe, which has an ID of 1.44". Close enough. The flanges, however, were about 1.6" at the openings so I decided to turn down some small sections of straight pipe and jam it in there.

 

The idea is to keep the ID consistent all the way from the head to the turbo.

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If you look back at anyone who has built headers for these, even for natural aspiration, they always have a big thick exhaust flange.  The reason for this is on a long inline six the expansion that occurs from one end to the other is pretty drastic. 

Okay, stop.  Are you looking for help with a VG header or for the L-series header that you are showing pictures of?

 

I was going to sit out when you said VG, but if we are talking L-series then I'll put in my $.02...

 

I agree with the above comment regarding the flange. You'll have a lot of trouble getting getting everything to line up with the ports without one, especially after a heat cycle or two.  Next, for an L-series, DON'T EVEN CONSIDER building this without expansion joints to accommodate the afore-mentioned expansion.  The tubes always will take more heat than the flange and will therefore expand at a considerably different rate than the flange.  If you don't have bellows or slip joints the header WILL warp and/or fatigue and fail.  

 

Here's a link that talks about a good OEM (Mercedes) source for a bellows:

 http://forums.hybridz.org/topic/29475-problem-with-european-kn2-turbo-exhaust-manifold/?hl=+mercedes%20+bellows

 

Burns Stainless used to source stainless slip joints - they probably still do, but you might have to call them.  either will work.

Edited by TimZ
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Your welds have insufficient gas shielding (ashen or gray beads), too much heat, and you are not running a back purge (or not enough) and you're getting carbides (sugaring) on the inside of the tubes.  They will fail through cracking fairly quickly.

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I called stainlessheaders.com and the sales associate who seemed very knowledgeable said they can make me a stainless flange for $100 and weld my header for $300. The only thing is their flange will be 3/8" thick and small spacers will need to be welded on to make up the difference. And just to be clear will it need to be one piece? Thanks.

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  • 3 weeks later...

I would recommend using cold rolled steel for the flange as it has a lower CTE vs SS.  Bolt it to a piece of 0.5" steel when welding to keep the flange from warping.  Also, if going 0.065" you need to use 321SS as the 304SS will crack.  You can get away with 304SS if you use the thicker schedule 10, which is likely a better choice due to space contraints and the tightness of the bends required.  Make sure you purge with TIG or use Solar Flux B instead of purging.

 

As Tim stated, use slip joints or make sure you have plenty of bends to help absorb the thermal expansion to avoid cracking.

Edited by 240Z Turbo
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