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Old 05-11-2013, 08:02 PM   #1
drewvdw
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Default Newbie to fabrication, need advice.

Alright, a buddy offered his old Holset HX35 to me for free and I'm going to need a fabrication project for school, so I'm going to be making a custom rotated setup for my car. I'm going to be starting my fabrication class in 6 weeks, so I figure that gives me a little time to figure out a few things. I'm thinking I'll shoot for somewhere in the range of 450-550whp. Of course, the turbo needs a rebuild and I'll probably be doing an HX35/40 hybrid with a billet compressor wheel to get more flow.

First of all, what kind of steel should I use? I used to know, but for some reason I can't think of it at the moment, it isn't 341, is it? Also, what diameter would you think is best? I may be making a full exhaust system and am considering going to a 3.5" turboback, but I'm not sure what diameter to use for the header runners/up pipe. I also will need to source some flanges for this.

Does anyone have any advice for a first timer? I'll have instructors helping me out, but I'll take any help I can get.
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Last edited by drewvdw; 05-11-2013 at 08:08 PM.
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Old 05-11-2013, 08:45 PM   #2
RockNRace03
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the first advice i can offer to you is practice makes perfect.

i've been a tig welder/fabricator at a custom exhaust shop for a little over a year now and can definitely tell you that there is so much to learn!


things i have learned.

1: take your time, its not a race. the more time you spend making sure things line up and fit with no gaps, the easier it will be to weld and the less it will move.

2: tack things when you can, nothing is worse than trying to hold 4 pieces with 2 hands and rotate them to try and figure out how they fit. one or two little tacks will make it so much much easier to test fit things. and they aren't hard to undue if things need to be adjusted

3: weld as you go if possible. if you have 5 welds in a section and try to weld them all at the same time, things will warp and shrink causing you a ton of frustration. if you would like to tack it all together for mock up, thats fine, but plan on having to un tack a few sections to re-adjust it

4. get a second opinion. sometimes you don't see things that look out of place or out of radius because your mind lies to itself because you are sick of spending an hour on one little piece of tubing.

5. pie cuts work, but personally look bad. the less welds the better.

for headers i would recommend 304 stainless tubing. .083 sidewall would be ideal, but .065 would work too.

i believe the exhaust ports on the engine are 1.75 inches. so maybe try for anything between 1.5 and 1.75 inch tubing. dyno tuning would tell you whats best. but any of those sizes would probably be fine, maybe see what other companies use.

i buy bends for side work from mandrel-bends dot com ( we bend our own at work)

if you have any more questions let me know. i dont know it all by any means, but im glad to give advise where i can
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Old 05-12-2013, 02:24 PM   #3
drewvdw
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Default

Thanks for the info, I'm almost positive that we've got a tubing bender at the shop since a lot of people make a roll cage as their project. Any ideas on where I could get some flanges? Or am I going to have the pleasure of making them myself? Also, you said go with 1.5-1.75" tubing, is that inner or outer diameter? Just briefly looking around, I found a place to get 1.76" inner diameter tubing, but it has a .12 sidewall, is that a bad idea to use or would it be fine? I'm planning on having the header and up pipe coated by Swaintech if that makes any difference.

PS, I just got reminded of how much I love this site, I went to a Cummins forum for advice on the turbo and haven't gotten a single response, I posted here about fab stuff and in the built motor section about turbo advice and I've got some decent info already
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Old 05-12-2013, 03:20 PM   #4
Loscaldazar
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Just try to get some scrap metal (the more similar to what you will be using in your project, the better) and weld it till you can't anymore.
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Old 05-12-2013, 08:27 PM   #5
RockNRace03
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i was talking outer diameter, but to get the inner just subtract the side wall thickness, you dont want to to be too thick though, or it could hold in heat, but if thats all thats available to you, go for it! its a fun learning experience, if its not perfect, you can always go back and learn from your mistakes! just keep an open mind and know that its not easy, take the frustration and laugh it off. practice makes perfect
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Old 05-13-2013, 12:33 PM   #6
DeleriousZ
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Most important thing about fabrication is fitup. If your fit sucks, it's just going to spiral downward from there.
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Old 05-13-2013, 02:14 PM   #7
Zefy
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Quote:
Originally Posted by drewvdw View Post
Thanks for the info, I'm almost positive that we've got a tubing bender at the shop since a lot of people make a roll cage as their project. Any ideas on where I could get some flanges? Or am I going to have the pleasure of making them myself? Also, you said go with 1.5-1.75" tubing, is that inner or outer diameter? Just briefly looking around, I found a place to get 1.76" inner diameter tubing, but it has a .12 sidewall, is that a bad idea to use or would it be fine? I'm planning on having the header and up pipe coated by Swaintech if that makes any difference.

PS, I just got reminded of how much I love this site, I went to a Cummins forum for advice on the turbo and haven't gotten a single response, I posted here about fab stuff and in the built motor section about turbo advice and I've got some decent info already
.120 wall is WAY to thick. 0.083 should be about the max in my opinion.

Also, tube benders for sch40 or DOM will not work with exhaust. It will crush it. Go buy mandrel bent sections and cut them to fit. Your school will most likely not have a proper mandrel bender for exhaust tubing.

A good starting guide I found was this 6 part series on youtube. It's a good starting point to learn about what it involved in making a header. Compliment this with your fab classes and a bunch of practice, you should end up with a pretty nice result.

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Old 05-17-2013, 07:04 PM   #8
drewvdw
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So really, 321 would be the way to go instead of 304.
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Old 05-17-2013, 09:02 PM   #9
bugeyesubie
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Yes for weight and longevity 321 is the best way to go, if you are just looking for a cheap way to learn use 304 first as 321 is almost double the cost.
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Old 05-21-2013, 04:39 PM   #10
DeleriousZ
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That's a pretty good video series Zefy, thanks!
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Old 05-25-2013, 10:58 PM   #11
drewvdw
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Does anyone have an estimate on how much tubing I will need for the header?
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Old 10-22-2013, 02:15 PM   #12
T-WRX13
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Use the stock header to get in the "ball park" for the amount of material usage, and then add in a little extra, because when you are first learning you will need it. If you end up with spare material it will ALWAYS come in handy on another project down the road.
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