Header Welding Tips Needed

[MR P-BODY]

The headers I showed were on my race car and it sets 4" off the ground... if you get into a problem
you can oval them... you will get a VERY small reduction in area(in most cases it wont hurt).. the 4"
is the lowest point in the front... I use to have the car at 3.5" off the ground but it was a PITA to load
on my trailer even with extended ramps

[CDMBill]

My TIG skills are still 5th grade, but I've built multiple headers with a MIG and the set on the car are doing great at six years old. I did everything with the MIG except the flanges which were done by a good buddy, certified TIG welder as we did inner and outer. I also had them coated which is the greatest invention ever for exhaust tubing. I also built them as step headers which makes fabrication easier IMHO.

For your super low profile set-up you may net benefit from a stepped design, but like Mr. P-Body i use the largest radius that will fit off the flange at as uniform a distance as possible. I couldn't get equal length but really pushed to get similar total bends in each primary along with a cone in the collector and putting the primaries into the collector in a circle by firing order. I really don't know if those things work but I copied stuff I saw at Burns Stainless.

[MR P-BODY]

My TIG skills are still 5th grade, but I've built multiple headers with a MIG and the set on the car are doing great at six years old. I did everything with the MIG except the flanges which were done by a good buddy, certified TIG welder as we did inner and outer. I also had them coated which is the greatest invention ever for exhaust tubing. I also built them as step headers which makes fabrication easier IMHO.

For your super low profile set-up you may net benefit from a stepped design, but like Mr. P-Body i use the largest radius that will fit off the flange at as uniform a distance as possible. I couldn't get equal length but really pushed to get similar total bends in each primary along with a cone in the collector and putting the primaries into the collector in a circle by firing order. I really don't know if those things work but I copied stuff I saw at Burns Stainless.

I've never seen a HP increase by putting the primary tubes in a certain location when it
comes to the dyno.... at least if the tubes were the same length... as soon as the tubes
merge into the collector they are all equal and draw the same IF the temps were close...
on a BIG percentage of headers I made I put a probe at 1" from the flange(all the probes
were precisely 1" from the flange to monitor distribution of the manifold for A/F reasons)..
you can see the bungs on my headers shown
EDIT
I actually made 2 sets of headers with equal tubes and mounted them in
different locations for the same engine... when dynoed we seen zero difference
but I was interested from some stuff I learned over the years..... thank you
to Chrysler for all my dyno time.... and I spent a LOT of time doing header work
over a 6 year period

[Scott Liggett]

I watched my friend TIG weld headers for his turbo'ed 6.0 LS engine. They taped the ends of the tubing, then fed Argon gas into the pipe. This cleaned up the welds inside the pipe and also reduced the ridges.

Now, I have seen headers crack because the exhaust does not give when the engine moves under load. Stainless is much more likely because it doesn't seem to be as flexible as mild steel. The exhaust on cars that run through the frame rails don't allow the pipes to move and that pulls the headers. That will cause the least flexible part of the exhaust to crack.

[MR P-BODY]

I watched my friend TIG weld headers for his turbo'ed 6.0 LS engine. They taped the ends of the tubing, then fed Argon gas into the pipe. This cleaned up the welds inside the pipe and also reduced the ridges.

Now, I have seen headers crack because the exhaust does not give when the engine moves under load. Stainless is much more likely because it doesn't seem to be as flexible as mild steel. The exhaust on cars that run through the frame rails don't allow the pipes to move and that pulls the headers. That will cause the least flexible part of the exhaust to crack.

Stainless is basically a soft material BUT has a lot of abrasion in it(as in cutting it)... think of it
this way... you wouldnt buy SS bolts to hold big loads but they look good on a intake and will
hold that easily
EDIT
It can become brittle with too much heat on the welds... I built 1 set of headers out of 316SS
and another 304SS ... if a car has a stainless exhaust its 304 which has a very good life span...
Also... a few other things to do for the headers to live is... cut the flanges between any ports
that you can... also make 1 hole larger than the bolt so it can slide and not buckle the flange
as in(if you have 2 bolts per tube make 1 larger).. if 3 holes per set of tubes the center bolt
wil be the normal size but the outers will be larger to allow slipage

[SuperBuickGuy]

I'd avoid dissimilar metals - I suspect that your original cracking issue with the stainless was because you used better rod than the material. The Chinese love 430 stainless, ironically the cheapness of the material means less nickel yet - here's the irony - less nickel makes 430 a better header choice. It will, however, rust... problems arise when you weld the stainless with 304, 312 or 316 rod - it has higher nickel content thus when it heat cycles the metal moves at different rates. So presuming you welded with 'normal' stainless rod, it caused more cracks - it wasn't (oh good lord will this probably get me flamed) the Chinese headers that were the problem.

Everdure - silicone bronze - is great for filling holes; it is not great for strength and cracks quite readily. Thus, using it to fuse steel pipe together will probably result in lots and lots of cracks (wherever there is strength needed) coating the headers won't keep it from cracking - but it will probably irritate you when you see the coating chipping off.

[Orange65]

Has anyone tried annealing the welds after the fact? Thermal stresses from welding would be relieved and if the heat is slowly reduced allowing the metal to cool slowly, the metal will anneal to a softer state as opposed to rapid cooling in air. This might minimize or eliminate cracking.

[JeffMcKC]

Filling the tube will help the weld, a lot of guys will also use the thicker tube right off the flange, and it may have been welded to hot, very low amps to weld the tubes with. Once its on the car Stress and harmonics can be killers

[DanStokes]

My friend Steve Smith (Specialty Fabrications) in MI is one of the few guys on the planet who can make double wall headers that live. The expansion rates are amazingly different but the double wall keeps the heat pretty stable in the exhaust stream which helps turbos a lot. He did some for us at EPA, along with a ton of other stuff. When he was at Watson Engineering he did a ton of headers for Ford R&D. I can pass his number along if that would be helpful.

Mr. P-Body - was the dragstrip shot from Milan? Kind of looked like it. Happy memories.

Dan

[BKBridges]

This thrtead has been great re: solid info!
Im going to cheat big time and start with a set of hedman hedders with a flange and primary tube set-up that fits the car. I had to chop the collectors and last 4" of pipe off to avoid my frame rails. Now I need to decide if Im going to go "all the way" with some 40" long 1 3/4 tubes or wimp out and end up with a set of pseudo shorty headers. This car is my daily driver and gets driven everywhere (like off road, drag strip, slalom, etc.) so I do need a lot of ground clearance. Need to get more argon.
BKB

[JeffMcKC]

build some 4-2-1 s Ebay Nascar headers plenty cheap lots of merge stuff on them

[MR P-BODY]

My friend Steve Smith (Specialty Fabrications) in MI is one of the few guys on the planet who can make double wall headers that live. The expansion rates are amazingly different but the double wall keeps the heat pretty stable in the exhaust stream which helps turbos a lot. He did some for us at EPA, along with a ton of other stuff. When he was at Watson Engineering he did a ton of headers for Ford R&D. I can pass his number along if that would be helpful.

Mr. P-Body - was the dragstrip shot from Milan? Kind of looked like it. Happy memories.

Dan

Yes that is Milan.... I was there testing with Chrysler and they would always let
me bring my car out to make some passes(I worked with a team called DCAE)
that was young engineers and was teaching them basically how to build/hot rod
a car/truck... was a fun project.... I use to build the headers on all of those cars

[BOOOGHAR]

Gary P from the Drag Week board needs to come over and see this, ive been following some headers hes been fabricating on FB for the past couple of weeks, they are more like works of art than headers

[Barry Donovan]

Filling the tube will help the weld, a lot of guys will also use the thicker tube right off the flange, and it may have been welded to hot, very low amps to weld the tubes with. Once its on the car Stress and harmonics can be killers

harmonics is a word.
I learned from the same model engine, an old log open jet carb, to a feedback carb with an o2, to a wideband with an o2..

the o2 wideband keeps headers pretty the longest. Frequency stuff. I learned it plays with up to 1khz. if you are into equal length, good math, it comes back to you.

304 can do anything..stay nice as to hanging too tight on any car.

preheating any combo as objects by themself works great, and the enlarging at leats one hole is clever too.

I have an upside down headering, and even needed to sleeve into the head.
the drama went onto changing fuel ratio because of the way stainless acted versus regular. same size stuff.

very precise is a header.

[SuperBuickGuy]

This thrtead has been great re: solid info!
Im going to cheat big time and start with a set of hedman hedders with a flange and primary tube set-up that fits the car. I had to chop the collectors and last 4" of pipe off to avoid my frame rails. Now I need to decide if Im going to go "all the way" with some 40" long 1 3/4 tubes or wimp out and end up with a set of pseudo shorty headers. This car is my daily driver and gets driven everywhere (like off road, drag strip, slalom, etc.) so I do need a lot of ground clearance. Need to get more argon.
BKB

here's where I built headers for my Buick using much the same principle (bought a box of tubes for a 454 kit).

http://www.bangshift.com/forum/showthread.php/11037-1970-Buick-Skylark-part-II/page10?highlight=skylark

starting at post 94