Header Building

don-f

don-f

Well-known member
I just thought I would share. I was starting to build a header for my 70s GTC Civic being restored for vintage production racing.
I started printing pieces on a 3d printer to help mock up the thing. This helps a lot. I can tell you what doesn't work pretty easy now without wasting a lot of time cutting and welding. They are reusable if you are careful pulling them apart. The parts are modeled after the 3" radius bends I have.
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I built a jig for cutting tubes for the collectors also

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The collector jig gets things close, but each tube is slightly different so requires some hand fitting. Burns has nothing to worry about, but it will do. The materials for the plastic bits are cheap. About $30 total for what I have made with many mistakes and I broke a few. The parts take a long time to print but they run without being watched so its OK.
 
David Dewhurst":26mcxegc said:
Not trying to bust don-f's balls but not very one has access to a 3D printer. :D A friend with an H Prod car bought one of these sort of header kits. He was/is a happy camper.

https://www.penntoolco.com/icenginework ... mkEALw_wcB
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It was not intended to be a solution for everyone, its not an easy path. If you don't want a printer don't buy or borrow one! Its not for everyone I was not telling anyone they had to do it this way. There is a steep learning curve. Projects on the printer do not always go as planned, you are basically extruding plastic with a refined chinese toy, not the highest quality at all. The good news if you have a problem, there is probably at least a hundred other people that have had the same problem and already posted a possible solution online. The header parts have to be printed in PETG, its a bit more trouble than PLA. You do have to learn CAD (Fusion 360 is free for 3d printing files) and a slicing program to generate G code. I have a lot of pieces printed and there are things I would reinforce if doing them all again. Its just a process, but lucky mine is almost done design wise. If someone wants my files they are welcome to them, but really most are better off doing it from scratch if the diameter and radius is not the same. Once you do have the setup and skill though its not just header parts you can make. I made this AXA tool rail for my Boxford lathe over the weekend. No more shelves and drawers! https://www.thingiverse.com/thing:4877281

The big thing with commercial header kits... Can you buy one for 1-3/8" diameter? No! What about when you need a different tube radius mine is 3" but I may need a few 2"? Maybe a 11.25 degree part instead of the standard 22.5 curve? The base commercial kit is very limited. What happens when you need more of one part and need none of the others? Break or step on one? I have done both more times than I wanted to. Neither solution is perfect commercial or DIY, but it works for me. The investment is not so much that when I am done playing I cant just set it on a shelf and let it set for a year or two until its needed again.
 
I buy the E bay header with the flange that fits, the Goose SS tube and a collector set . Set the collector where you want it and work from the head to the end . Lots of slices . You have to design with welding in mind or you screw yourself . So,often you need to make an area of the tubes , weld that section complete and move on. Oh, it changes shape as you weld .
30 hrs maybe
 
Here is how the plastic pieces attach to the metal stubs for mockup. Its a dorman temporary freeze plug. I think the box of 5 was under $20.

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One homemade merge collector. I need more welding practice and its not perfect but its will be a good enough start for now. It was good practice and I think there is only about $20 in materials. The preformed cone that's not attached yet cost more than the 2 u bends I used to make it. The backside in between all the tubes was a pain to get closed up good. I ended up using a mig and point and shoot. There was no room to do much else. let alone get a standard tig torch in there.

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This is what I am thinking routing wise. Keeping the exhaust out from under the oil pan keeps it from getting crushed and keeps the heat away from the oil too. Waiting on a few bends from UPS this week. The plastic bits have some slop in them and sag in and down so the real routing will not be as close to the v belt pully like shown in the picture. I still like them though for figuring out the tube layout.
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For test fitting of stainless pieces take a pair of narrow hose clamps and tack 3/4 long strips between them. Then you can rotate the pieces intil you get it correct and tack weld between strips. I have about 10 of these I use for header builds.
 
If you have something you want to print, send me the .STL file and I will print it. My printer sits idle most of the time.
 
I uploaded the stl files to thingiverse if someone needs 1-3/8 header mockup parts. I have two mild steel tubes tacked and these really do make it easy to get the same shape in steel, it went fast and its clean. Just waiting for the different radius bends to show up now. Here is a link to the files. https://www.thingiverse.com/thing:4886707

Steve Eckerich":anwrn0wl said:
For test fitting of stainless pieces take a pair of narrow hose clamps and tack 3/4 long strips between them. Then you can rotate the pieces intil you get it correct and tack weld between strips. I have about 10 of these I use for header builds.
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Good idea! Thanks!
 
I spent a lot more time working on the collector than I did worrying about equal length. Pipemax says 1-3/8 primaries, 27 to 29 inches long and 1-1/2" choke in the collector so that's what I am shooting for. A really good forum to read what really works for headers is speed-talk.com. Equal length that most people get laser focused on has an effect but its about 5th on the list they give for designing a good header and the other criteria is much more important. One of the more interesting threads is the one where one member who builds headers for a nascar team put that to the test and made a 8" primary log manifold and ran it against his best designs. Its a 21 page discussion "Log Manifold lessons!" in the advanced section that you have to sign in to see. There are other examples also the same header builder made a header for a vintage tr4 in the 200 hp range and made very significant gains also. There is a horrible header someone used for an example that was "equal length" and that's all the builder put a priority on and it was used as a "what not to do". Here is a quote from another thread "I think Calvin said that pipe length is the least important thing, even in NA engines, even less in turbocharged I think. So just use right size primaries, smooth bends, and length is whatever it becomes. Someone's theory was that if a positive return pulse is timed so early, very short pipes, that it reaches the cylinder during blowdown, or at least way before TDC, it can't do much harm. When cylinder pressure is more than double the exhaust back pressure then back pressure has no effect." I do have a chassis dyno so if the thing ever gets out of the shop, I could test and see. At this point though I will be happy if it makes it to an open track and runs dead last.
 
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The hose clamp tip was useful! A few more hours and it should be close to done. I have a cone for the merge collector on the way.
 
Its all tacked. I have a lot of welding practice to go and some misc parts like a support bracket and the collector cone, but its getting there.
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David Dewhurst":10yeiocz said:
If you were trying to get equal lengths, how close did you get?
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I measured it today with a tape measure. 3 tubes are close, within an inch and a half. The #3 cylinder is worse at four inches shorter than the longest tube at twenty eight inches. It is not a big deal to me. I am happy to just be making progress and moving the project forward. I bought the car in 2005 and pulled it apart in 2007/8 so its been a long time blocking up the space in my garage.
 
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