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need advise for building my own headers

4K views 44 replies 17 participants last post by  1971BB427 
#1 ·
I want a set of fender well headers for my little 87 Nissan P/U with a 302 {5.0 L} motor and drive train ...I going for that Gasser look ...I'm going to have to build them myself but I've never attempted it before and want to ask a few questions BEFORE I get started...
First off....Is there any kind of material made for mock up ,like pvc pipe ?something ez to bend that holds its shape well, it'll take a lot of time and money mocking it up with steel pipe,especially if it dosent work...it seems there should be something made just for this.

my second question is....are there any rules to making a set of headers ?like all the tubes have to be the same length, I don't know where I heard that but thought I'd ask.

third question what size primary tubes should I use? It'll have to be steel and not stainless because I have no way to weld stainless nor do I have the experience to weld stainless....I believe its a stock 302 with a 4bbl carb since it idles nice I don't know if it matters much but my plan so far is to have something like a 4" side pipe that will also be used as a step (it has a body lift ) heres a pic of the truck showing theres plenty of room
 

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#5 ·
electricians pizza oven

electricians use a heat box to warm pvc conduit and make custom bends. If you leave it in too long it will melt-burn the pipe. You need heavy welders gloves to hold th conduit untill it cools. having someone spray watter wil speed up the cooling. I saw a rear engined 34 roadster the builder fabbed to mockup tube frame, used holesaws to make the cuts all iv pvc first.
 
#6 ·
I have done several sets over the years. On Chebbies.. 1 5/8" tubing is common for most of these. The Fords usually have smaller exhaust ports so probably can get away with 1 1/2". It probably depend on what flanges/kit you use.

I found that the aluminum material that air cooled VW engines use (looks like small dryer hose) from the fan housing to the heater port works excellent for mock up. I used to buy it by the foot inexpensively and five/six ft. is usually enough to do plenty. It bends and keeps the bend till the next tube is fabbed. Common wire coat hanger can also be used to "eyeball" bends.

Years ago I made a deal with a local muffler shop and had them take 8-10 ft sticks of my tubing and bend series of "U" bends in each stick. This gave me plenty of stock for bends. Still have a couple of sticks left.

Mig welder and chop saw will serve you well. :thumbup:
 
#7 ·
Not sure if mocking up from PVC or anything else will really help that much. It's going to be a trial and error, even with a mock up, as matching the sample will still be difficult. I usually start with the rear tube and tack it together to set where the others will go. Then tack each tube together as you move forward. Once they're all tacked, cut each from the flange, and weld each one together. After that they can be fitted to the flange on the vehicle, and tacked again. Then remove and do the final flange welds, and collector install.
I've used small rod and a brake tubing bender to just hold up and see where there might be an interference issue, but thata's about all I've used it for.
 
#8 ·
Without having viewed the above videos (or any videos) which couldn't hurt to see, I'll just give you my own tips...ideally these comments and my cup of coffee end at about the same time...

It can take a couple tries before your headers start to look good, so be patient. Don't shy away from do-overs when it's just not coming out right.

1 3/4 primary diameter is good for an SBF. Use 16-gauge u-bends, wherever you get them from, instead of the thinner 18. Why not have your headers last a little longer after all that work?

You can start with an old set for that-type motor and just cut the tubes back to where you can work with them, instead of dealing with a new flange if you want.

To design (and this is my method only, 'cause there are different ways): Make a steel or aluminum plate (say from 2x1/4" strip or whatever) that bolts to the head in a couple places, then drill/tap 5/16-18 holes where the center of the exhaust ports would be, and run old bolts through them so they stick out a ways with the plate fastened to the head. This is your fake practice flange. Get a coil of 3/8 aluminum fuel line (it's really soft and bendable) and cut/straighten 30" (or what ever you choose) sections to represent equal-length primary tubes...and jam onto those bolts sticking out the head. Cut a piece of 3/4" wood to serve as a radius mandrel for bending over, make the radius the same as the c/l of the radius that the header tubing you bought is (i.e., if your tubing bends are a 6" radius inside...that plus half the actual header tubing diameter, minus half the fuel-line tube diameter). Now bend the aluminum around the wood to make fake header tubes at the right radius, keeping them the 1 3/4" apart and working with the cut length. Have "tubes" be either straight or bent at the right radius along any particular portion, just like the real ones will be. Don't cheat. You can do it over and over on each "tube", bend/straighten/bend again, until you get four tubes laid out that all wind up next to each other down where you want the collector to be. You can tape tubes to each other w/ masking tape using wood blocks as separators for temporary. You may wind up with a lot of masking tape on there. You can work out all your routing this way, before making a cut on your real and somewhat costly material.

If this is sounding complicated or a waste of time, actually you should get this far before lunch (often headers are a 3-day job) and you'll get a much better result if you start this way (i.e. having a plan) instead of just getting busy welding before you know how the tubes need to be shaped. If there were one or two only to do it would be different, but four tubes all needing to snake around and work with each other and clear chassis components and starters and end-up equal length is another story.

Once you have a suitable design (did I mention, have spark plugs in the head and be thinking about maintaining access), again keeping those tubes equal-length and changing bends to have them all end up in the same place, you just more-or-less reproduce it in the real material and you don't have to be exact. Measure straight lengths, and portions of angle and transfer that to the real stuff. When cutting bends, it can be tough to get a "square" end, marking before hand with masking tape helps. You want each tube to end up looking like it was bent from one piece and not having sudden sharp angles happening, either in a straight part or in the middle of a radius bend. Having a Makita or similar 4" angle grinder handy helps a great deal as you go along fitting each joint.

Do only tack welds, especially at the flange and collector, until the whole rest of each tube is the right shape. This ensures you can pull a tube out and do a proper weld all the way around a splice joint. Once tubes start getting welded in all the way, weld access on an adjoining joint can be a problem. As you progress, you'll be pulling your design set and installing the real set, over and over but it's worth it to get it right. Header building is as much about strategy as fabrication. Take breaks, sit and look at what you've done and think about what's next for awhile before actually doing it. Almost every mistake you make when you realize it, you'll be able to trace back to impatience.

Looking at an existing header collector and flange, you can see how they did it there (you'll have bought your collectors from the same place your u-bends came from) or anywhere. Spark plug clearance shaping can be tricky, a ball-peen hammer is helpful. Monkey-see-monkey-do...

Ooops, coffee's all gone and we're not even done yet. Anyhow, when you've got it the best you can do it, weld it all up good, maybe grind a little here-and-there for appearance and if it really came out nice consider having it coated, inside and out, after you've used them once or twice and know they're not going to need any more work. Headers get red-hot under hard use, and they rust too...Why have to do it all again in a couple years?

Good luck in any event, my hat's off to anyone who tries such a project for themselves.
 
#11 ·
Boy ,you can say that again Sam, I'm pretty confident I can get started now.
1 3/4 tube ,the aluminum flex tube sounds cool and ez to get just the right look I want too. So it wasn't just BS about all the tubes being the same length, good to know too.
Now, one more quick question about something I heard or read just to confirm.
Lets say I use the1 3/4 tube ,would it be better for low end power to have a smaller tube about 2" long welded to the flange and then the 1 3/4 welded over that, also to the flange ,if its a slightly better I'll do that too.
Ok, I think I'll get started ,I'm off to find some aluminum flex pipe...and a new camera...so I can get some feedback...
Thanks guys, as usual ya'll came through for me again
 
#12 ·
Actually, smaller-than 1 3/4" overall as mentioned in other posts would probably be the best for low end...just if you're doing fenderwells, like race stuff, it might look better to go with a race size. Call it an artistic choice. As far as going with step features etc, you'll probably be busy enough just doing it the simple way, to get started, without getting too trick. Your choice, however, that's what we have hobbies for.:cool:
 
#13 ·
it looks like the smallest aluminum flex tubing I can get is 2" but as far as looks go I feel 2" looks best,then I had another idea to shoot past you guys.
if I used two flanges on each side I could bolt one to the head with the 1 3/4 X 2" long stubs and the second flange with the 2" would slip over that...does that sound workable? I've seen two flanges on race cars the first flange bolts to the head and the second set has a different bolt pattern that bolts to the first flange so they can run bigger primaries..... no dimples
 
#14 ·
If you want 2" to start at the head you will have to do the dual flange and bolt pattern arrangement, as 2" can't be fitted to the stock bolt pattern, there isn't enough room.

2" is going to just murder your low and midrange power though, would need a 9500+ rpm Super Competition engine to need 2" tube on a SBF.

1-3/4" step header starting with about 8-10" long 1-5/8" tubefrom the head flange would be a nice size for the engine you have and trick looking fenderwell header.

Take a good look at the weld-up kit you buy from some place like Summit or Jegs, most are just unwelded T-Bucket Roadster headers/Sprint car headers/tube frame drag car headers and won't have any u-bends....they will just be 4 prebent primary pipes, 2 collectors, flanges and bolts, made to weld yourself into a premade straight over-the-frame-rail setback engine placement design that won't clear your tire.

www.schoenfeldheaders.com is a good source for the parts you will need....flanges, a couple boxes of random bends(because you will need a variety of J and U bends with different length legs) collectors and bolt rings, gaskets and bolts.

Don't get too hung up on having all the tubes the exact same length, as long as you are within about 4" you'll be fine....as you have no way of knowing what the ideal tuned length is.... you could make all the tubes exactly 29" long, only to learn on the Dyno that the engine needs 36" for best power....so all that time spent making perfectly equal 29" tubes was a waste of time.

All that having the tubes be equal length does is tune the header to a specific point in the powerband....without testing several sets/lengths you would be very lucky to just hit that spot for your engine....having all the tubes unequal just loses out on that high peak at a specific rpm but spreads that peak out lower over a wider rpm range....some say that is a better thing on street headers (Hedman does).

There is a computer program called PipeMax that is very extensively used to accurately pick primary tube diameter, length, at what distance out from head a step should be, collector size and length, etc but it is quite expensive for someone who isn't using it on a regular basis.
 
#16 ·
If you want 2" to start at the head you will have to do the dual flange and bolt pattern arrangement, as 2" can't be fitted to the stock bolt pattern, there isn't enough room.

2" is going to just murder your low and midrange power though, would need a 9500+ rpm Super Competition engine to need 2" tube on a SBF.

1-3/4" step header starting with about 8-10" long 1-5/8" tubefrom the head flange would be a nice size for the engine you have and trick looking fenderwell header.

Take a good look at the weld-up kit you buy from some place like Summit or Jegs, most are just unwelded T-Bucket Roadster headers/Sprint car headers/tube frame drag car headers and won't have any u-bends....they will just be 4 prebent primary pipes, 2 collectors, flanges and bolts, made to weld yourself into a premade straight over-the-frame-rail setback engine placement design that won't clear your tire.

Schoenfeld Headers - Manufacturer of competition headers is a good source for the parts you will need....flanges, a couple boxes of random bends(because you will need a variety of J and U bends with different length legs) collectors and bolt rings, gaskets and bolts.

Don't get too hung up on having all the tubes the exact same length, as long as you are within about 4" you'll be fine....as you have no way of knowing what the ideal tuned length is.... you could make all the tubes exactly 29" long, only to learn on the Dyno that the engine needs 36" for best power....so all that time spent making perfectly equal 29" tubes was a waste of time.

All that having the tubes be equal length does is tune the header to a specific point in the powerband....without testing several sets/lengths you would be very lucky to just hit that spot for your engine....having all the tubes unequal just loses out on that high peak at a specific rpm but spreads that peak out lower over a wider rpm range....some say that is a better thing on street headers (Hedman does).

There is a computer program called PipeMax that is very extensively used to accurately pick primary tube diameter, length, at what distance out from head a step should be, collector size and length, etc but it is quite expensive for someone who isn't using it on a regular basis.
I didn't realize the 2" would make so much difference good thing I mentioned it ...so I'm back to 1 5/8 into the 1 3/4....just got back from lowes ,I didn't think they would have any flex tube other than the dryer vent so it I may to to order something on Monday if its not to pricey...
 
#15 ·
What do you have to work with? As mentioned this can be done with a chop saw and a mig welder. I've prefer a metal cutting bandsaw but have done this with a sawzall or a portaband and a good vise. Not only does a good vise come in handy to holdthe tubes for cutting a medium to large vise works to shape the tube end to the header flange.
While it's nice to have access to TIG welder both mild steel and stainless can be MIG welded. If you fit up is expertly done you could oxy/acetylene weld up mild steel but all the weld joints will rust out before the rest of the tube because the metal gets so hot the steel picks up oxides in the HAZ area. Lastly there is the arc welder. Beg, barrow or rent a mig before you even dream about this. With perfect fit, 5/64" rod and expert skills this could be done. There is 1/16" rod but the only thing it is usefull for is a bad example of what welding rod is.
Even if you have a mig welder make a set out of mild steel before trying stainless. Stainless is so expensive you want to get to the point that you make few mistake before you wiork with it.
 
#17 ·
I have pretty much everything to cut steel including an industrial horizontal bandsaw, plasma cutter ,chop saw 4 1/2' side grinders and even tube notchers and then all the air tools and metal shaping stuff, sheet metal and fabrication is kinda my thing...Tools I don't need, knowledge is lacking ,although I know a whole lot more tonight than I did this morning..I just got off the phone with my friend who's a drag racer and he said the same thing about the tube length...he also said having a good custom set of tig welded headers made is at least 1,000.00 ....2-300.00 and my own free time is more what I'm after so as long as I don't have to worry about all the specifics and stick with the 1 5/8 -1 3/4 primaries I should be ok and I'm free to let my imagination run wild. that sounds good to me...now for some quick mock up material so I can get started...BTW thanks for all the links im going to check them out right now.
 
#19 ·
Usually the best place to start is to get a you weld them up set of headers from someplace like speedway motors. These kits are really reasonable priced. This will get you a starting point of straight ana bent tube to cut up and the flanges will be precut and drilled. You can get a set of flanges with stub tubes already fit and welded but they are a bit pricey. By the way a $1000 for a good set of custom headers would either be a set thats super easy to make or a very good deal. When everyone ask where you found headers for that The feeling you'll get when you say "I made them" is priceless.
 
#20 ·
For the flexible ducting in a size you need, go to your auto parts store, it is used as the warm inlet air heat riser tube from the exhaust manifold stove to the air cleaner snorkel on a bunch of 1960's-1985's cars. They are likely stocked up on it at this time of the year.

Only thing I could find at Speedway Motors were T-bucket type roadster header weld-up kits, doesn't look like a good enough assortment of bends to do a stock frame rail and engine compartment fitted fenderwell header to me. No U-bends
 
#30 ·
I gotta admit that mock up kit IS cool and if I was building headers for a living it would be a must have tool. and on the occasion the grand kids get dropped off at the shop for pawpaw to watch, they could play with it all day in the office. I've got the PVC and since the exhaust ports are all the same for SBF, I can order the flanges and collectors along with the kit itself. this should be a fun little project
 
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