building custom headers


Staff member
theres a great deal of useful info in these links , and sub linked info so don,t skip over them without looking thru carefully, as theres years of experience to be gained
yeah its amazing how everything costs ten times what you think it will and takes five times longer to do even at that inflated price
BTW, its not really all that rare to find that the headers you have present a spark plug wire clearance issue,


that makes installing the spark plug boots in such a way that they don,t contact the hot metal surfaces almost impossible , this can sometimes be helped a great deal by the addition of a header flange, or SPACER PLATE, that MATCHES YOUR PARTICULAR ENGINES CYLINDER HEAD EXHAUST PORT AND HEADERS,


thats significantly thicker being welded to the existing header flange , to space it out further away from the cylinder heads, obviously you don,t want to do this without testing all the clearances so installing the extra header flange with an exhaust gasket on both the cylinder head surface and between the header flange spacer and the existing headers as a test is strongly suggested as a test.



heres where you get spacer header flange plates




Accel Extreme 9000 Ceramic Wire Sets

ACCEL now offers the cure for burnt spark plug wire boots with Extreme 9000 Ceramic Wire kits. The 8mm Ferro-Spiral core wire now has ceramic boots on the spark plug end of the wires that will withstand up to 2,000° F. If you are running headers with close tolerances, an engine bay with little room, or an RV with boots that melt because of heat, these wire kits are the answer. and yeah! youll still need the heat resistant plug boots to prevent the wires from melting past the ceramic plug boot

at times you need to do some minor fabrication to get things to fit & function, so having a welder and knowing where to get header flanges helps, but some careful measuring will yield surprising results at times, like BIG BLOCK CHEVY HEADERS CAN BE MODIFIED TO FIT A 500 CADDY ENGINE

you might want to install a 496 big block chevy in a 1969 AMX, and a DANA 60 rear differential, that will require a bunch of carefully measured custom fabricated custom components, something any true hot rodder can do with the correct tools like a decent welder and access to a mill,but you won,t find the parts required in any catalog.
if you have ever done the math required to calculate the ideal header dimensions for a serious big block engine youll find most headers would require longer header primary tube lengths, closer to the 36"-39" length and using the 3.5"-4" collectors at least 18"-22" long that are rather easily built with the side exhaust design but almost always too restrictive to fit for clearance issues with an under the car exhaust.
or put a different way, the basic lay-out of a properly designed side exhaust lends itself more easily to a max effort exhaust,provided you junk or replace the highly restrictive inserts and replace them with some other option
lsheadflowd.jpg ... sionLR.pdf ... brication/

viewtopic.php?f=56&t=1303&p=16831#p16831 ... ipe_dream/ ... ipe_dream/ ... index.html ... usion.html ... g-137.html ... -gauge-74/

viewtopic.php?f=56&t=185 ... _list.html ... erRevA.pdf ... index.html ... g-137.html ... sions.html ... ndex2.html ... t/page.htm

viewtopic.php?f=56&t=352 ... OK-2956HKR ... ctors.html Flanges.htm

now obviously the exhaust lego kit the links point too, is a better route but I never knew they existed until recently and their kit of fabrication parts, is very expensive..

Ive done this many times its not that hard. here is what I do, get some of that plastic smurf tubing in the 2" diam. size and some ceiling hanger wire and some of that hard set construction insulation foam. now weld 1" stubs of the exhaust tube to the header flange exhaust ports and bolt it to the cylinder heads. clamp the collectors to a 6 foot section of 2x6" wood and jack it up solid under the car (collectors not touching the car anywhere)to position them where you want them under the car, now cut (8) sections of smurf tubing too about 36"-42" long(theres a formula to figure the exact length)slide 4-6 pieces of ceiling suspension wire in each tube with the ends looped over inside the tube. now starting with the upper inside collector position and the rear exhaust port, bend and fit the smurf tubing to fit, the next forward exhaust port goes to the lower inside collector port the next exhaust to the upper outside collector port and the furthest forward to the lower outside collector port , once they are all bent to fit shoot the tubes full of hardening construction foam, let it harden and then pull each individual tube off one at a time and duplicate it in steel tubing, by cutting and welding sections and dozens of trial fits before you permanently weld ANYTHING!(or have your local muffler shop duplicate it,.. MOST WON,T AS ITS VERY LABOR INTENSIVE) this method REALLY makes the fit and try time minimal.(YES ITS STILL A ROYAL P.I.T.A.) and assures equal length tube headers.SMURF TUBE is flexible plastic electrical conduit that's normally BLUE or ORANGE and COMMONLY called smurf tubing by contractors its a plastic version of that metal GREENFIELD tubing that electrical contractors use but its cheaper and easier to work with, it resembles a canister type vacuum cleaner pickup hose but stiffer, its available at big hardware stores,and electrical supply houses dirt cheap in 10' lengths about $6 each or less you will need (3)BTW the 4-6 wires act like re-bar in concrete, the loops keep the wires from moving in the foam while their encased in the construction foam, the hard plastic foam is what keeps it stiff and no it will not be exact you will still need to tweak it to get it to fit but it will speed up the process of making the tube pattern shapes. just keep in mind that you can buy headers fairly cheaply (under $300 in many cases) for most cars its when you go and get an odd ball combo this comes in handy, like putting a 502bbc in a 57 vette or a 392 hemi in a 63 falcon.

example , my 383 vette has a cam with exhaust cam timing that opens at 83degs bbdc, thats 97 degs atdc,
Bore: (Inches) 4.03"<BR>Exhaust Valve Opening Point: (Degrees ATDC) 97 degs
Peak Power RPM: 5500rpm Calculated information appears below
Header Pipe Diameter: (Inches) 1.84"<
Header Pipe Length: (Inches) 37.65
Collector Diameter: (Inches) 3.5
Collector Length: (Inches) 18.82
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Staff member
as a tool junkie.....damn this looks nice (would be nice to be filthy rich....would it not!)so you could afford to put 3" stainless exhaust like this on all your cars


in the ideal exhaust system youll want to have less than .5
(thats 1/2 a PSI of back pressure) at the engines peak rpm




keep in mind installing an (X) almost increases the effective cross sectional area, of the dual exhaust ,or collector cross sectional area to double what it had been behind a single header collector, by doubling the area that the exhaust flow sees, dropping the restriction to flow almost in half


3" o.d = 2.87" diam. inside--approximately 6.5 sq inches of area
2.75 o.d = 2.62"diam. inside--approximately 5.4 sq inches of area
2.5 o.d = 2.37" diam. inside--approximately 4.4 sq inches of area
2.25 o.d = 2.12" diam. inside--approximately 3.5 sq inches of area



well worth reading ... ndex1.html








ITS extremely important that you ask questions and get accurate answers , BEFORE purchasing headers about what style cylinder heads the headers are designed to fit, below is pictured a set of headers obviously designed for factory strait plug heads but bolted to a set of angle plug heads making spark plug access and wiring a clearance and heat , destroying ignition wire nightmare



It really looks like those headers ,in the picture you posted directly above, that, your using were designed for use with the angle plug heads,
and use of the strait plug heads causes the spark plug to header tube,
and related ignition wire clearance issues.
this is, unfortunately a very common miss match of components.
look at the heads and the exhaust header tube routing and the difference in clearance,
that the designed angle plug heads use would make on spark plug to header tube clearance.
one of the least understood yet common problems is that the header manufacturers seldom bother to tell you what cylinder heads were used during the header design phase of production of the headers and damn few people purchasing headers bother to do the research or ask detailed questions until they run into problems caused by the design miss match, and yes its very common to find headers designed for strait plug heads can cause similar issues if used with angle plug heads , but that's slightly less common

Some people think that angle plug heads produce more power than straight plug heads. This common misconception is not true! In reality, the ONLY benefit to angled plug heads is to provide more spark plug boot clearance with some header designs.

The idea of these designs producing more power came from some early angle designs that placed the plug location closer to the exhaust valve. This WILL create more power, but straight plug designs that have since been moved in the same fashion produce the same power.

BluePrint Engines offers both straight and angle plug design heads – your choice should be based on appearance and cost – not on one being more powerful than the other.

– Tech Tip courtesy of BluePrint Engines"



angle plug

viewtopic.php?f=56&t=3155&p=8423#p8423 ... chines.htm

keep in mind most header manufacturers are primarily concerned with making a PROFITABLE, and EASY to MANUFACTURE IN QUANTITY product, and TO PRODUCE AND EASILY INSTALLED HEADER , the power level , or rpm range its most efficient in, is a SECONDARY concern.
most headers will have primary tube lengths that are to short for max power.


Design Software

Header Design Articles And Tips


adding an anti-reversion baffle to a 18"-24" longer collector on open headers with the internal pipe about 1/2 the collector length tends to help scavenging on some engines

some guys do exceptionally nice fabrication work,



If you can,t find a decent quality header there are ways you can build a custom set-up, just a a custom set exactly to the correct length for your application, with the correct collector.
obviously youll want to do a few basic calculations and realistically assess your intended power and rpm range
but don,t get crazy, a good set of full length commercial headers may give you 70%-90% of what a custom header that costs three times as much will give you, especially if your using an exhaust system and its restriction to flow behind the collectors

you start by clamping the collectors where you want them after measuring to allow room for the correct primary tube length, and bolting the header flanges to the heads with the engine in the car, read thru the inks for ideas

theres readily available calculator info in the links posted below so take the time to read thru the linked info and sub links as it can save you days of work and a bunch of cash
theres pre-cut header flanges

theres pre-welded collectors, its really not all that difficult

yes I had built and used a similar custom designed, or lets say extensively modified set, on my 1965 Pontiac le mans with a 496 BBC engine
they worked great!

the fast route is to buy these and carefully measure cut old headers and weld them on

but due to the restricted clearances you are generally better off visiting a muffler shop and having them fabricate 8 short sections of expanded exhaust tube (they may need to be angled first) with both ends of a 2"-4" long length expanded to slide over each primary tube in the cut header and extension, obviously careful measurement is critical here


IT would be hard to significantly improve on this basic lay out

LINKS YOU'LL WANT TO READ ... ndex2.html


knowing a few constants in engine pressure and flow helps

an engine usually requires approximately 2.257 cubic feet per minute per horsepower to maximise intake flow and exhaust flow at about 115 cfm per square inch

so assuming your building a 500 hp engine / 2 (divided by 2 as there's normally two header collectors on a v8) we have 250hp per header collector, (open header collectors) multiply that by 2.257 cfm and you see you need 565 cfm and divide that by 115/square inches and we see we need a 4.9 square inch minimum exhaust collector pipe, per side (open header collectors).

as a cross check 500hp /8=1129/8=142 hp per header primary , 2.257 x 142/115=2.76 sq inches 0r a header primary a bit larger than 1 3/4 and smaller than 2" or a 1 7/8 to maximize peak hp, per header primary, but keep in mind you'll spend most of your time below peak rpms so a slightly smaller 1 3/4" primary on a street strip engine that sacrifices a bit of peak hp for better mid rpm torque makes sense, and once you install longer exhaust pipes and mufflers you'll need to step up the exhaust pipe size cross section past the header collectors or they will tend to be restrictive at the minimum size the formula predicts



I got asked if swapping to custom header collectors was worth the effort and if 4-2-1 collectors worked?
Ive done it easily a dozen or more times and its never HURT, a few times it failed to produce noticeable gains but most of the times it improved low and mid rpm torque and broadened the torque curve, many factory headers are too short to provide ideal power curves, obviously do the math and measure first, because getting it correct helps, getting it wrong just costs money and takes time and probably ruins your current headers, BTW a TIG welder and BACKING the weld with shield gas helps.
keep in mind its not likely to be a huge improvement, your likely to gain 20-30 ft lbs in low rpm torque and 5-7 hp in the mid rpms, but peak hp might even fall 3-4 hp, but your average torque generally improves and picking up a 0.10 in the 1/4 mile is not UN-common in my experience, and don,t make the common mistake of cutting off the old collector and welding on the new extended collectors without carefully checking angles and clearances under the car, its amazing the number of guys that never think about clearance and routing issues until after they weld on extended collectors



heres a few pictures of 4-2-1 collectors off the internet
summit sells these
you ideally want to have a 4-2-1 config to maximize the engines power potential with the exhaust primairy tube size just a bit larger that the heads exhaust port size, with each step up in diam, in a 4-2-1 config header where two smaller tubes join a larger remain as small as practical while still allowing the twin feed pipes to fit into the larger pipe they feed into,thus the internal area of a 1.625" primary pipe, (as an example ) is about 2.01 sq inches, so at least in theory a 2.25 inch diam could be swaged to fit and allow the twin 1.625' primary to feed, but in reality the 2.5" is going to be more practical taking the tubing wall thickness into account, Id then feed both those into a single pipe of the smallest practical size that will physically fit

I generally just buy the set of these and weld them on,to the primaries cut to 36"-38" as it saves a great deal of work and the results have proven to be similar, ideally the two collectors feed into an (X) pipe with fairly long tail pipes as this seems to help the torque curve be a bit broader , even if it does cost a few peak ft lbs

CORSA came out with a more efficient DUAL (X) PIPE exhaust and headers for the c7 corvettes, the increased scavenging effect of dual (X) pipes is something I've promoted for decades
MY c4 vettes exhaust looks similar to this


Ive always been amazed at the number of guys who think the only options they have in components , they can use on a car, involve buying and installing parts listed in a catalog.
adding a dual (X) to the exhaust system has proven to reduce the decibel level and spread the torque curve on several corvettes, Ive done that mod to the exhaust on,as it tends to increase the cylinder scavenging efficiency,and reduce the exhaust back pressure, and I read that modifying headers in a similar manor is worth .05 seconds on several cars, so don,t think a bit of thinking outside the box as they say won,t pay off in a bit more power or power over a wider rpm band.

headerxc.jpg ... ngray.html ... ngray.html

heres the new corvette dual (x) pipe




cylinder fill efficiency is a compromise, your engine design is forced to make selecting the way components are matched, the factors of cam timing compression and exhaust header tuning all must fall in the same 3000 rpm power band and ideally in the same 1500 rpm range to maximize power.
the choices between cam timing and compression ratio, and head and intake flow rates, valve size and valve lift and duration,
has a huge effect on,exhaust scavenging and while most people think the port flow rate is mostly the result of the piston dropping away from TDC,
lowering the cylinder pressure , thus drawing in the intake runner charge, this is not the major factor once the engine rpms increase significantly.
its exhaust scavenging during the valve over lap , being well matched to the engine displacement and cam timing, header diameter, and length, and collector design,
and intake ram tuning that can significantly boost cylinder fill and cylinder scavenging efficiency rates.
OK, first fact! the piston can,t compress anything being trapped in the cylinder by the piston compressing it as it raises,until both valves seat & seal










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Staff member
248 piece 2" exhaust lego kit!online-store/csgx/!/2000Series-PRO-PLUS/p/44994033/category=11578480!howitworks/c1se

Also, to choose the best welder for yourself,
you can choose any one of these.



more related links and info

don,t forget the vapor from welding stainless is toxic wear a mask


wpb02c7f34_05_06.jpg!howitworks/c1se ... ipe_dream/

225 piece 1.75" exhaust lego kit

there are times when changing header flange design, or using adapter header flanges, helps ease fit/clearance issues








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Staff member ... index.html

theres more info in the article but these bits may help ... ipe/Detail
you can use what ever welder you have access too, both mig and tig can be used to build headers,
but given a choice ID suggest TIG and don,t forget to back flush out the air and use duct tape,
to temp, seal the tubes being welded, to limit oxidation inside the header tubes if you go stainless.
header flanges up to about 1/2" thick are available commercially for the more common engines,
if you need thicker you might want to buy doubles in 3/8" header flanges ,
and use one as a spacer, between the headers and heads
The primary header pipe diameter is determined using basic engine mechanical specifications, such as: Bore Stroke Compression Ratio Valve diameter Cam specifications (lift and duration) Target rpm range
0310Phr Burns 03 A Z

"The overall length of the primary header pipe is governed almost exclusively by the target engine's rpm range, which is dependent upon wave tuning. Typically, a lower engine rpm range likes a longer primary pipe, while a high rpm engine prefers a shorter primary."

While typical off-the-shelf street 4-into-1 headers do not have secondary pipes, Burns' research has proven repeatedly that his Tri-Y designs make more overall power over a broader rpm range. While traditional lines of thought have street enthusiasts knowing Tri-Y pipes make more bottom-end torque, further research by Burns into the design have resulted in headers making more power all across the rpm range. With more components as part of the Tri-Y design, more tuning possibilities exist, and therefore more potential lives within.
0310Phr Burns 04 Z

"The secondary pipe diameter is determined by considering both pressure waves and reflective waves throughout the system. Since the pipes are paired according to the firing order, these waves can work together or against each other. Naturally, our designs work with the waves to increase the efficiency of the header, using the wave pulses to help pull gases from the engine.

"There are two basic kinds of waves we're dealing with. First, there are pressure waves. The pressure wave travels the length of the primary pipe in a 4-into-1 header, then is reflected from the collector where the area changes from the small-diameter primary into the larger-area collector. A reflection of negative pressure goes back up the primary pipe.

"In a Tri-Y design, the pressure of additional area changes (where the primary pipes become secondary pipes) produces additional reflections, so the Tri-Y must be designed in a different manner with respect to wave control. Given this, the area of the Tri-Y header between the first and second collectors becomes critical, and tuneable. The entire header is affected by this crucial length of pipe, and can be fine-tuned accordingly through proper sizing for optimal broad-range performance.

"The 4-into-1 pipe is also affected by altering pipe lengths, of course. But, without these secondary pipes it is impossible to tune with the same level of precision as with the Tri-Y headers. It's for this reason we prefer the Tri-Y design in most applications. The tuneability is so much more accurate, we're able to find more power over a broader rpm range. This is especially critical in engines expected to work well over a wide rpm range, like street machines."

Another huge reason for the move to Tri-Y headers is weight savings. Burn's claims most of their Tri-Y headers weigh in at about _ the weight of comparable 4-into-1 pipes for the same application, due to the smaller pipe diameters used throughout similar applications. Also, with less internal volume than comparable 4-into-1 headers, the Tri-Y equipped engine is typically more responsive. Tri-Y designs require physically smaller collectors as well, contributing further to space and fit concerns, and adding further to crisp engine responsiveness.

"There is much power to be found in researching collector design and size. The optimal collector is determined by several variables, and it's engineering interacts with the entire exhaust system. The internal volume, the outlet size diameter, and the angles at which the pipes come together within the collector are all factors that must be maximized for the header to perform to its full potential."

1 - Primary Pipe Entry Size
"Our computer model design program determines many of these hard dimensions based on data gathered over many years, including the length and diameter of the primary or secondary pipe entering the collector."

"The pipe entry angle is typically between 10-20 degrees, with most pipes being right at 15 degrees. The cone (or goilet) formed between the pipes as they transition from primary to collector is formed as a consequence of these angles, nothing more. The mass of gases moving through the pipe does not want to change direction, so keeping these "pyramid" cones true to the pipe entry angle helps smooth the transition from the relatively small volume of the feed pipe to the larger volume of the collector."
0310Phr Burns 06 Z

"The collector outlet diameter is the most critical dimension in the header. It's what makes the merged collector work the way it does. Each collector we sell is custom-sized to each customer's engine, and there's no real 'formula' to get a broad-based general determination for street machines. As a rule, the overwhelming majority of aftermarket headers designed for the street market have way too big of a collector outlet diameter. Most street guys are losing power because of badly designed, manufactured, or engineered street headers. There is much room for improvement here."
0310Phr Burns 05 Z

"Overall collector length is not critical. Once the other variables in the header design have been determined, the collector ends up being as long as it needs to be. We've found no benefit in lengthening or minimizing this dimension. It's more important to properly engineer what's going on inside the merged collector, and let the length determine itself once all the other important factors are optimized."
0310Phr Burns 07 Z

One of the growing areas of research at Burns is the critical area just aft of the all-important collector outlet. Burns' dyno research led him to begin experimenting with interchangeable venturis, which slip into receivers just aft of the collector. While these prototype dyno parts were initially crafted to assist Jack in determining the critical overall collector diameter size, he soon realized they could be a marketable product. His initial "DynoSYS" product for dyno research evolved into a line of interchangeable sleeves called the Burns Tuneable Exhaust Collector, or BTEC for short.
0310Phr Burns 08 Z

The BTEC system has shown capability to alter the entire power curve of the engine. By changing only the insert, racers can change the entire tune on their engines to fine-tune for track conditions, weather, or driver preferences. Mostly used by drag racers, many in Pro Stock, the BTEC system offers enthusiasts a glimpse into the future of header design. While the drag racers have already embraced the benefits of BTEC, a number of road racers are beginning to experiment with the system as well.

Burns is also working with stealthy reverse-cone megaphones, which perform a similar task. While much information regarding the use of his reverse-cone megaphones remains secret, street enthusiasts should understand the use of these products is still primarily confined to open (unmuffled) exhaust systems. Therefore, there is little to be gained at this point in time from digging deeper into the design. In the future, products like this may impact the street market, but at this time they are purely race-only parts.
0310Phr Burns 09 Z

One area street machine enthusiasts are aware of is the evolution of the X-pipe. Early on, connecting the left and right halves of a true-dual exhaust system with an H-pipe resulted in measurable benefits. This theory evolved into the X-pipe, which allowed both left and right portions of the exhaust system to share some common flow area and resulted in even greater gains in power with a notable reduction in exhaust noise. This win-win situation prompted Burns to research even further, and his X-pipe designs stand among the finest and most-effective in use today.
0310Phr Burns 10 Z
Here's a look at a typical...

read full caption
0310Phr Burns 10 Z
Here's a look at a typical NASCAR Winston Cup header, as designed and manufactured by Burns Stainless. Naturally, construction is all stainless steel, each pipe is researched for optimal performance, and many portions of the pipe are interchangeable for fine-tuning. This is a GM SB2 header; Ford- and Mopar-based headers are quite similar.

"Our X-pipes are designed for maximum inertial flow, and unlike other X-pipe designs, exhaust flowing through our X-pipe sees a minimal direction change. By minimizing the entry and exit angles of the X-pipe, we were able to limit the restriction through the unit, and find more efficiency. Exhaust flow does not like to change direction, so this is only logical.

"Most of our race customers still do not use X-pipes, but interestingly most of the NASCAR Winston Cup teams use them in their restrictor plate cars. For a street enthusiast, they are highly recommended."


Within the 300 series of stainless steels, there are four types that are suitable, available and cost effective for the racer. These are 304, 316L, 321, and 347.

321 and 347 are known as stabilized grades of stainless. These are alloyed with either titanium (321) or columbium (347), both of which have a much stronger affinity for carbon than does chromium at elevated temperatures. This eliminates carbide precipitation leaving the chromium where it belongs for corrosion protection...remember our discussion of intergranular corrosion? Both 321 and 347 are top choices for exhaust headers, especially turbocharger systems and rotary engines. Since 321 is much more available than 347, that leaves 321 as the first choice, with no sacrifice in needed qualities.

316L is an extra low carbon (ELC) grade of stainless that has only .03% carbon, making less carbon available to precipitate with the chromium. It is used extensively in marine exhausts where salt water corrosion mixed with diesel exhaust particulates and electrolysis create such a horrible environment that even other grades of stainless cower and run away!

304 is the most inexpensive and available stainless in the 300 series. It is suitable for normally-aspirated header applications, and has been successfully used by many racing teams. It does not have the high temperature fatigue resistance that 321 does, but is considerably less costly and much more available. Most 304 tubing these days has the dual designation of 304/304L.

Practically speaking, there are overlapping applications of 304 and 321 stainless in header construction, but knowing you've got the insurance of the aircraft-grade 321 for the job is definitely worth consideration of the extra cost... if your application requires it.

Stainless steels come in both tubing and pipe sizes. Since certain pipe sizes are almost identical in dimension to tubing sizes, pipe may sometimes be substituted for tubing, and vice versa. Numerous wall thicknesses are available, but for headers, normally .049" (18-gauge) to .065" (16-gauge) is used.

Different specifications are used to meet particular requirements for the military (MIL), the American Society of Testing Materials (ASTM), and the Society of Automotive Engineers (SAE). Examples of what to look for when you order stainless tubing are as follows:

ASTM A-554 304 stainless is a welded mechanical tubing used primarily for ornamental purposes. It is not fully annealed and is work-hardened slightly in manufacturing. It has good column strength and good bendability. ASTM A-269 304 stainless is a general service commercial specification that is higher quality and is fully annealed for better ductility. It is available in both welded seam and seamless, and is a good spec for the racer to use. We have not seen any difference in longevity between welded seam and seamless stainless tubing in header use, but there is a substantial cost difference. The column strength is not as good as A-554, but it has excellent bendability with a higher cost due to the full annealing.

MIL-T-8808/8606\MIL-T-6737 321 stainless are military specifications for aircraft tubing. Suffice it to say that some MIL-specs are not necessarily better or even as good as some ASTM standards. There is no particular magic here.

There are as many uses for stainless steel as there are projects in the shop. There is nothing else that transmits an image of quality and skill to the majority of fabricators than a cleanly constructed stainless steel project. Whether it is a set of headers, intake stacks, or even a stand for one's dyno engine cooling fan, stainless steel has such great mechanical properties that its use should be considered for many projects beyond exhaust systems."


headers with this basic lay out produce both good peak hp numbers and a wide torque band ... usion.html









Tech: Five Tips On Building A Set Of Bad-Ass Race Headers


A good set of race headers accomplishes one major task in particular; they help your high-powered engine to breathe more efficiently, and a byproduct of that efficiency is more power, especially when the headers are built properly.

In this article, we’ll cover some of the finer points of fabricating a sweet set of race headers, covering things to look for during the process, challenges that may occur, and even a couple of welding tips that will make the process easier to digest.

The folks at Burns Stainless, along with the guys at REF Unlimited, recently invited us to follow along with their process of creating a set of headers that exhaust the energy provided by a state-of-the-art supercharged small-block LS engine.

Theory And Background

Tuning the exhaust system is just as critical as tuning the engine, and in order to cover the rest of the process, we need to provide a bit of background.

In a four-stroke engine, as the exhaust valve opens after the power stroke, the cylinder pressure initiates exhaust blowdown. At this time, a pressure wave traveling the speed of sound (1,700 feet per second) travels down the exhaust pipe, and as the valve continues to open, the exhaust gases, moving over 350 feet per second, flow over the valve seat and out the exhaust pipe. These two different aspects – gas particle flow and pressure wave generation – are what we’re trying to streamline during the creation of a proper set of race headers.

A quick video of the inner workings at Burns Stainless

“The objective of the exhaust is to remove as many gas particles as possible during the exhaust stroke. The proper handling of the pressure waves in the exhaust can help us to this end, and even help us “supercharge” a naturally-aspirated or nitrous engine,” says Vince Roman of Burns Stainless.

Each pressure wave arrives at the end of the exhaust pipe, and part of it is then reflected back towards the cylinder as a negative pressure (vacuum) wave.

The engine and vehicle parameters required for Burns to use their X-Design program, which assists in specifying optimum header dimensions and materials.

If the pressure waves can be timed properly, through the selection of the proper tubing lengths, collector diameters, and pipe arrangement in the collector, the exhaust pulses will work to scavenge each cylinder, and also help to start the intake flow into the cylinder on the next go-round.

“Since the pressure waves travel at near the speed of sound, the timing of the negative wave can be controlled by the primary pipe length for a particular rpm. The trick is to tune an exhaust system to produce a negative wave of the proper strength timed to occur at cylinder overlap,” Roman explains.

Using a proprietary parametric exhaust modeling computer program called X-Design, Burns is able to give the fabricator a solid starting point for header construction.

This program takes into account a multitude of factors; manifold type, number of valves per cylinder, camshaft specifications, header configuration, cylinder head style, and even the race fuel an engine will consume.

Once the information is loaded into the program, it will then spit out recommended dimensions for the header, from tubing diameter to collector size and more.

X-design spit out these parameters for the headers constructed as part of this article; it was the job of Holman and Clouser to reproduce these parameters as closely as possible.

Tip #1 – Material Selection

For the headers constructed here, 304 stainless steel was chosen. Stainless steel (in both 304 and 321 grades) has exceptional high temperature characteristics, especially when compared to much-heavier mild steel and even aluminum.

One advantage to using stainless material is its low coefficient of thermal conductivity, meaning that no ceramic thermal barrier or header wrap is required to keep the exhaust energy inside the pipe – the steel accomplishes that task as a function of its low-carbon construction. 304 stainless is much more common, and costs less than the aircraft-grade 321 material, making it a common choice among fabricators during header construction, unless the engine in question uses a turbocharger, in which case 321 is a better-performing material due to its high-temperature fatigue resistance.

Some of the assortment of parts used in this header build - 304 stainless U-bends, Burns merge collectors and six-inch mufflers, and stainless flanges designed specifically for the cylinder heads on this vehicle.

“These many characteristics, such as superior heat retention properties, high temperature fatigue resistance, and to a lesser extent, the cosmetic value of a non-rusting finish, combine to make stainless steel an ideal choice for headers and exhaust systems,” says Roman.

In terms of weight, although aluminum is much lighter than stainless steel, exhaust tubes undergo a great deal of stress during the engine’s heating and cooling cycles, making aluminum an unsuitable material for header construction.

“It is important to note that yield stress for metals is a function of temperature, with most metals becoming weaker (i.e. lower yield strength) with increasing temperature,” says Roman.

An Extra Tip - Sensor Placement

If the user has a set of EGT probes, the positioning of these items also need to be taken into account. More importantly, every single one needs to be positioned at the same distance from the port to ensure consistency in the reading from each cylinder. Burns suggests 1.5-inches from the port exit as a minimum. This particular application also had the probes laid slightly back from vertical to assist in valve cover removal in the pits.

Oxygen sensor location also needs to be taken into account during the fab process. “The rule of thumb is to install the oxygen sensors from the three o’clock to nine o’clock position so they’re never aiming down,” says Holman. Roman adds that the reason behind this is so that condensed water will not pool around the sensor, as it will cause the sensors to break due to thermal shock once the exhaust gases hit the sensor.

Aluminum is one of those materials. Although the material has excellent strength properties at lower temperatures (and lower weight than stainless steel), once it reaches the high temperatures common in exhaust applications (1100°F) it is close to melting and has virtually zero strength. 304 stainless steel is actually weaker than heat-treated aluminum at room temperature, but as the heat goes up, it loses little strength, while aluminum approaches its fatigue point much more quickly.

Along the same lines, mild steel and titanium are also not the optimum material for header fabrication.

“Typical 1010 carbon (mild) steel conducts 219% more heat per foot than do the types of stainless steel we use in header fabrication. By contrast, quite a bit more heat stays inside the stainless header tubes and does not get passed into the surrounding air. By not allowing the contraction of the cooling gases as they flow down the tubes, more exhaust velocity is retained which promotes better scavenging at the collector. This retention of velocity increases the overall header efficiency,” says Roman.

With the modeling software at hand, Burns is able to determine not only the optimum lengths of each header tube, but also whether a step, or multiple steps will help the engine to perform most efficiently. The software also spits out recommended material amounts required to produce the header design specified.

Tip #2 – Tubing Length

The biggest challenge to making a proper set of race headers is easily the process of making them fit into the car, and that’s where REF Unlimited’s Greg Holman and Rob Clouser come into the picture.

“For these headers, we ran the engine’s particulars through our software, specified the sizing and materials needed to meet those dimensions including bend radiuses and collectors, then REF took those dimensions and made everything fit into the car,” explains Roman.

The trick is to tune an exhaust system to produce a negative wave of the proper strength timed to occur at cylinder overlap. – Vince Roman, Burns Stainless

The headers for this particular application used a triple step into the collector. The first step used is 2.250-inch tubing, into 2.375-inch tubing, and the final step before collector entry is 2.500-inch tubing. Each step is seven inches long for a total tubing length per pipe of 21 inches. The collector used is one of Burns’ merge collectors that has a 4.250-inch diameter, and on the outlet side of the collector there is a megaphone that transitions back into a 5-inch diameter outlet at the end of the header.

“The first thing we have to deal with is what the customer’s looking for in general,” says REF’s Greg Holman. “We also have constraints to consider in terms of what Burns suggests for maximizing performance. Everything is a give-and-take.”

Left: Double-checking the outside diameter of some of the tubing. Right: Cutting off the flanged portion of the mufflers - these get V-band connections welded to one end to permit easy removal of the bullhorns.

In practice, the application required a bit of massaging from the original specifications suggested by Burns; as this particular car has factory front framerails, concessions needed to be made in order for everything to clear. REF needed to add a bit of extra length in the largest pipe diameter, or last step.
Tip #3 – Checking Clearances

Holman says that when a car is dropped off for a header installation and a discussion is had with the vehicle owner, he can just about visualize where each of the tubes will end up in order to maximize the header’s performance – a skill that comes with years of experience building race headers. This likely won’t be the case for a first-time builder.

“Another concern we have to watch for is the location of the collector. We have to determine how much room there is at the exit point, and whether there is the physical room to fit the parts. The collectors were so long in this application that we only had so much room left to fit the tubes into the collector between the frame and where the collector and muffler exit point is,” says Holman.

The Edelbrock LS-R-equipped LS engine used to fabricate the headers for this article. The collector exit location will be between the tire and leading edge of the door on each side.

Checking for steering clearance, master cylinder clearance, starter clearance, and other components that are installed in the car is a critical step of the process. The driver’s side of the vehicle will typically be the tightest location in terms of clearance, since steering components typically can’t be altered.

“We have to physically make sure that the header tubes are also in an order to where they can come in and out of the car. You have to consider removal of the cylinder head in the car and where the plugs can be pulled after every pass – all of that has to be considered as well,” Holman explains. “So not only do we need to take into account what Burns suggested in this instance for header lengths, we also have to consider what the car owner needs in terms of a service-friendly racecar.”

The U-bends stacked up and awaiting surgery.

With the exit point on this car between the front tire and the leading edge of the firewall, the collector was placed first – the collector can’t be moved once the fabrication process begins. Conversely, Holman says that in an application where the header exits underneath the car, the collector location can be changed slightly during the process, if necessary, to ensure proper positioning.

“Once the collector is in place, you have to figure out which is going to be your longest tube – it’s usually the driver’s side, furthest tube forward. When we determine length, we try to get every single pipe as close to the length as possible. If it must be longer for some reason, it’s always in the last step if the headers use multiple diameters,” says Holman.

Various steps of the tube mockup process. It's important in this application to place the collector/muffler assembly into position and work backward towards the cylinder head, as the muffler assembly can't move due to its location between the tire and body.

It’s not really a one-way street – every step of the process is a compromise. – Greg Holman, REF Unlimited

Firing order must also be considered, so that when the cylinders fire they go around in a circle into the merge collector, as this is what makes the merge work properly to scavenge the cylinders; each tube sucks the exhaust flow from the adjoining tube. Holman says that it doesn’t matter if the firing order of the tubes runs clockwise or counterclockwise around the collector. Unless there is a crossover pipe under the car – not typical in a true drag-race application like this – the direction is irrelevant.

Another quick tip Holman suggested is to use a socket and extension installed onto the spark plug during tube layout – this ensures that plug access won’t be hindered by the final tube positioning. He also works to ensure that plug wire clearance is sufficient to prevent burned plug wires and boots.

“It’s not really a one-way street – every step of the process is a compromise,” says Holman.

Tip #4 – The Use Of Merge Collectors

A merge collector does what the name says – it allows the exhaust gases to merge within the collector. The reason for using a merge collector is to allow the high flow and high velocity gases to increase and broaden the engine’s torque curve as much as possible all the way to the horsepower peak. The merge collector must be designed for the particular engine, and Burns does this with the X-Design software.

“The most critical area is the outlet of the merge collector – its shape and diameter. In a highly developed racing engine, the collector outlet interacts in an organic way with elements as far removed as the intake valve and camshaft and all the way to the tailpipe,” says Roman.

The craftsmanship inside the merge collector is evident in this photo. By putting the spike on the end of the incoming pipes, the collector helps to scavenge the flow from each adjacent pipe as the engine fires in sequence.

“For drag racing and similar applications where a tailpipe is not required, megaphones fitted with reverse cones are invariably the best option. They produce maximum horsepower and maintain the highest and smoothest torque curve. Megaphones also offer the highest potential power past the peak without compromising the lower end of the power band on well-developed engine combinations with optimally short-header tube lengths and a well-chosen collector outlet diameter.”

Tip #5 – Stop The Cracks

All stainless steel needs to be purge welded. For the uninitiated, purge welding is using argon gas to remove all of the oxygen inside the tube during the welding process, and there are a number of reasons for doing this.

“If you don’t get rid of the oxygen before you weld on the tube, your weld will be very rough and porous on the inside; it’s called a cauliflower weld. The material will also not melt together on the inside of the weld, and you’re creating a built-in crack,” says Holman.

If the purge welding process is not followed, the stainless material will only expand and contract so many times before the weld will fail. The purge welding process ensures that the welding rod will flow properly and fuse the material through the tube.

“The beads of the weld on the inside will actually mimic the appearance of the weld on the outside when it’s purge welded,” says Holman.

The far end of this header tube has the plug with the argon filler tube; the near end has the rag stuffed inside to keep the argon from leaking out while the welding process is underway.

“Everyone has a different way of doing it. We use a piece of copper tube on a regulator that we stick into one end of the tube, and plug the other end with a cotton glove or rag. We’ll turn the argon gas up to 10-15 inches of pressure to push all of the oxygen out. As you weld the tube, the leaks between material joints are getting sealed as you go. Instead of blowing back out the weld, it will push the gas out through the cotton material and keep the tube full of argon.”

Holman suggests that one of the secrets is to use the smallest diameter welding rod possible. “As long as stainless is melting, it’s hot enough. You never want to use a rod larger than what the gap between materials is; the largest rod we use is .035-inch,” says Holman.

In addition, the type of rod used needs to be a higher grade of stainless than the base material. In this instance the headers were built from 304SS material, so a 308SS rod was used. The higher nickel content in the 308SS rod helps to prevent weld cracking as the header undergoes heat cycling.

“The argon keeps oxygen away from the backside of the weld. On the front side, you have argon flowing from the TIG torch cup to keep oxygen away from the molten metal, which keeps carbides from forming. You need to do the same on the backside of the weld, hence back-purging,”says Roman. Burns also offers their Solarflux powder, which is mixed with alcohol to form a paste that can be brushed on the back side of the weld where possible to form a barrier to keep the weld oxygen-free.

“It may look like diamonds on the outside, but unless you purge weld and use the proper filler material, it’ll fracture,” Holman explains.

A finished view of the header from underneath.

In Conclusion

The challenge of fabricating a good set of race headers is a skill that evolves over time, and with careful planning, a solid direction, and the right information at your fingertips, it’s possible for even the garage fabricator to build a set that will perform, look great, and last. The tips presented here are not the be-all end-all of header fabrication; instead, they are some of the things that the experts take into account during the process
The completed header, five-inch Burns Stainless muffler, and bullhorn constructed as part of this article.
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Staff member
READ THRU THIS ... index.html





like most things EXPERIENCE HELPS, but if you mock up whats needed its not going to be difficult to do.
generally you carefully measure, the length and angles and buy a few pipes to cut and weld and use a pipe expander



to make one end female so you can slip the normal pipe inside a slip fit giving you some leway on exact length.


A GREAT DEAL of the results will depend on the exhaust header design,MOST commercial headers are designed with low cost and ease of installation in mind rather than max scavaging and max HP. KEEP IN MIND the main function of headers is to increase the efficincy of the SCAVAGING of the spent gases in the cylinder and help draw in the following next fuel/air charge in the intake runner of that cylinder,thru the use of timing negative pressure cycles,and reversion pulses in the exhaust port, but the exhaust restriction level behind the headers can kill most of the potential results from even the better designs, ANY SIGNIFICANT RESTRICTION TO FLOW AND RESULTING BACK PRESSURE WILL HURT YOUR RESULTS ,if your not willing to change the whole system to optomize the results , and lower the restriction to flow past the collectors on those headers, then a stock or modified stock or shorty headers will be a decent choice, if the FULL LENGHT HEADERS are MATCHED to a full length, 3" exhaust with an (X) that will significantly lower the restriction to flow rates. the stock corvette exhaust manifolds tend to be far better than most stock exhaust manifolds but they still fall far behind what a decent set of full length headers and a low restriction exhaust will do for your cars power.
design the system correctly and you can significantly increase the exhaust scavaging of the cylinders and increase power,do it wrong and youll hurt power.

readings above about 1.5 psi usually indicate a restriction thats costing you power.

the main IDEA is to REDUCE restriction and EQUALIZE the flow, AND INCREASE the CYLINDER SCAVAGING to help power by increasing the cylinder filling efficiency. side benefit is usually a more mellow exhaust tone
lets say your car has two 2.5" exhaust pipes, blending the flow thru use of an (X) doubles the area and cuts the restriction almost in 1/2, plus if designed correctly it helps scavaging, a single 2.5" pipe cross section is approximately 4.9 SQ" a single 3" has approximately 7 sq inches of cross sectional area, so adding an (X) effectively reduces the restriction almost in half but stepping up the size and adding an (X) beyond the header collectors does far more at reducing the restiction

THE (X) BY FAR is more effective, the (H) may equalize the pressure to a great extent but the (X) blends and exqualizes the flow, READ THRU THE LINKS AND PAY ATTENTION TO THE MATH

you can easily meassure this, get a pressure gauge and drill a 1/8" hole in the exhast behind the headers and bring the engine up to full throttle with the gauge attached, (I usually suggest running thru the gears on a semi hard accelleration test run with a partner in the pass seat watching the gauge readings, with a temp test line to the gauge running into the cab thru a window.

whats the differance?
lets say for the example the exhaust pulse is a quart to water moving at several hundred feet per second, but unlike water it can be compressed,since the exhaust pipe inside dia. is set the length of the pulse or slug of exhaust exiting the engine every 90 degrees of rotation (v8) has inertia/energy/mass, if it passes a right angle low pressure exit point, at first it flows into both routes but as the mass passes the opening a slight negetive pressure forms and it reverses and the flow changes, put a vacuume gauge on the (h) and it vibrates, wildly.
install an (X) and the flow from both sources is FORCED to BLEND, line up, equalize and BOTH sections of the up stream flow benefit from the
as each inertia/energy/mass, and slight negative pressure that forms, but its far more equalized. gases unlike liquids will expand to fill any void.
put another way if one side was pumping out dark green water and one side was pumping clear, an (H) would have dark green exiting one side and light green exiting the other, an (X) would have both sides an equal, slightly lighter green flow .now at low rpms , or with a smaller than ideal pipe dia. thats no big deal, but at high rpms, BOTH the SCAVAGING of the cylinders your trying too scavage enhances the effect and the reduction of the restriction to flow tends to be better with the (X) put a vacuume gauge on the (X) and it vibrates. but not to nearly the same extent, and the changes in pressure reading remain more consistant

BUT,DON,T be thinking that either is a mandatory huge improvement, it may or may not help the power, the degree of restriction, displacement, compression ratio, cam timing and the efficiency of the headers has a good deal to do with your results, and sticking restrictive mufflers on past the (X) or (H) can effectively kill most of the potential benefits
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Staff member
these pictures might help

Also, to choose the best welder for yourself,
you can choose any one of these.








IF YOUR WELDING STAINLESS USE A MINIMUM 16GA 18 GA is too THIN, FOR STAINLESS HEADERS OR EXHAUST PIPE, AND DON,T FORGET TO PURGE THE BACK GAS WHEN WELDING , and 321 is superior to 304 stainless ... rticle.htm ... onents.asp ... 6/10002/-1

IF YOU WELD STAINLESS EXHAUST PIPE without a back flush you can get weld crystallizing or SUGARING , an ARGON back flush and taping both ends to exclude oxygen helps reduce this significantly as will tig paste
and use of the solar flux paste and back flush , usually helps considerably in making a nice looking weld, if your building headers.


try to avoid crystallization it causes a restriction to flow and turbulence

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Staff member ... ipe_dream/



There are twisted individuals out there who don't want to put a Chevy in a Chevy and others who think the factory engine location doesn't always cut it when striving for improved engine fitment and the ideal front-to-rear weight bias. Either scenario leads to a place many of us never want to go when working with an oddball engine and chassis combination-the realm of the custom header build. Time-consuming, frustrating, and ultimately very expensive, custom pipes are the bane of every hot rodder's existence, unless he owns a tube bender and has a knack for geometry. Even then, every header-building artist still has a scrap pile of tube sections that didn't quite fit the project they were intended for. Wasteful. That nonsense ends today. Go ahead, stuff a BMW V12 into a Nash Metropolitan or slide your Hemi backwards in the chassis a few inches. With Icengineworks' precision header modeling system, even the novice fabricator can design and build his own pipes correctly the first time.

The kit is composed of rubber connectors that fit into a header flange to give a starting point for your primary pipe build. Interlocking plastic tubing sections of varying angles are marked to indicate the direction and orientation of one section to the next. You can literally twist together the primary pipes, snaking them around your project car's steering shaft, gearbox, firewall, control arms-whatever gets in the way. Once you settle on a header design, you can measure exactly how long the primary tubes are (the centerline length of each tube) and where to make the bends on a tubing bender. Or if you're on a budget and don't have a bender, you can simply buy tubing donuts or mandrel-bent, U-shaped lengths of tubing, and the modeling kit will show you exactly where to cut each tube so you can weld all the individual sections together to make your custom header. An included jig makes cutting the tubing on a vertical bandsaw easy enough for almost anyone to build his own pipes without making an expensive pile of scrap. The kit is as pricey as a set of coated headers but pays for itself the second time you use it.


Staff member
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Be a fun project to take on someday building custom headers for myself Grumpy.
Time is limited and funds not there.
For now adapting headers to fit is what I have done.
Cut & move header tubes.
Welded myself.
#1 Reason I abandoned the Corvette Racecar project.
I have 2 sets if Hooker #4202 Race headers for the 1970 Trans Am.
I know they perform.
2" primary & 3-1/2 collectors.
Tuned Nice. Near equal lengths.



don,t forget to duct tape off the interior volume and flush & purge any header tube your building,
with any mig or TIG (tig welds tend to be stronger) from any stainless tube or flange,
and coat the inside of the weld area joint seam with the paste linked to above, or any resulting weld that might look great on the outside surface will be a bit fragile ,subject to vibration or stress cracking and it will look like crap,( especially stainless)


the more I go back and RE- read through the links and sub-linked info,
on many of these threads,
the more I realize how little I know,
and how few tools I have,
I also find I either missed reading previous links
or new ones were added since I last read the thread!


The Grumpy Grease Monkey mechanical engineer.
Staff member
Trends In Header Technology
Article By Jim Kaekel, Jr.

It's common knowledge that one of the most cost effective methods of improving a car's performance is to install a set of free-flowing, full length exhaust headers. Headers not only increase horsepower, but improve throttle response and fuel efficiency. As it is with carburetors, camshafts or cylinder heads, bigger is not always better when selecting headers. Correctly sized headers are paramount to achieving peak performance.

Joe Beyea of Beyea Headers (Genoa, N.Y.) states that one of the most common mistakes is selecting headers with primary tubes too large for the application.

"Most people have it drilled into them that an engine is just an air pump, and that they can install the largest headers they can get," says Beyea. "In reality, they would probably be better off using a header with smaller primary tubes with a broader torque curve". An engine with larger tube headers may actually make more peak horsepower on a dyno, but at the sacrifice of low- and mid-range power, a loss particularly noticeable on a circle track car exiting a corner, or on a drag car at launch and after gear shifts.

The type of car/chassis, engine type/displacement, cylinder head/valve sizing and operating RPM range must all be taken into consideration before investigating the primary tube and collector dimensions of available headers. Dyno and track tests have proven that a header that is even an 1/8" too large will diminish low- and mid-range horsepower. The reason for this is that the primary tube diameter establishes the velocity of the exhaust gases as they exit the pipes. The tubes need to be sized so that they are big enough to not restrict the gases, but not so large that velocity is insufficient to scavenge the cylinders of all gases.

For popular engines, header catalogs often include several part numbers with varied primary tube and collector dimensions. Small, 1-1/2", 1-5/8" or 1-3/4" diameter primary tube headers are ideal for small displacement (283-383) engines, while larger, 1-7/8", 2" and 2-1/8" diameter headers work best with larger (396-454) cubic inch engines. Primary tubes with 2-1/4" and larger diameters are designed for 500+ cubic inch engines in drag race-only applications.

Once proper diameter tubes are selected, primary tube length, measured from the flange to the collector, is another important consideration. Longer primary tubes increase bottom end torque while shorter tubes increase top end power. Adjustable headers use slip-on collectors and primary tube length can be adjusted using varying lengths of slip-on tubing, usually in 2", 4" and 6" lengths. An existing set of headers may also be modified with an adjustable header kit. After the collectors are cut off, the desired length of tubing can be slipped on. Using weld-on tabs and related fasteners, the collectors can be re-installed and are now removable. Experimenting with different lengths of primary tubing during "test and tune" is now much easier.

Another primary tube variation involves "step" headers. Used by drag and circle track racers alike to extract that last bit of horsepower, stepped primary tubes progressively increase in diameter, usually in 1/8" increments, from the flange to the collector. The "stepped" tubes help increase exhaust velocity for that last bit of added horsepower. Stepped headers are typically offered in single- and double-step versions; a single step header may have 1-7/8" to 2" primary tubes. A double step primary tube header may go from 1-7/8" to 2" to 2-1/8" between flange and collector.

"Tri-Y" headers, where the primary tubes are configured per the engine's firing order prior to exit into a four-into-two-into-one collector. According to Beyea, the design uses the engine's firing order to "fatten up the torque curve", improving bottom- and mid-range horsepower when compared to traditional four-into-one headers. Because of their added cost, "Tri-Y" headers are typically seen only on high end race cars.

Recent advancement in header design has yielded the merge collector. Similar to four-into-one collectors, merge collectors have two distinct differences. A conical spear extends beyond where the primary tubes meet inside the collector to smooth the transition. A "choke" or reduction in the collector's diameter, roughly 6" before the outlet, minimally improves scavenging and is used only by racers wanting every last bit of horsepower. (30)

Header construction is also undergoing a revolution of such. Not so long ago, nearly all street or race headers were constructed from mild steel, however, stainless steel has been steadily gaining popularity. Although nearly twice the cost when compared to mild steel headers, stainless steel units offer virtual lifetime durability due to eliminated corrosion. Beyea says that due to the fact that corrosion is eliminated, stainless headers are not plagued with rust scale build-up inside the tubes and the associated loss of performance like conventional mild steel headers. Engine life is also improved since corrosion can no longer be introduced into the engine when the engine is turned-over.


The Grumpy Grease Monkey mechanical engineer.
Staff member


Today, advanced engine technology has helped the two-valve competition engine reach over 2.5 horsepower per cubic inch. Camshaft design and cylinder head technology has led the way to competition engines that easily spin well over 10,000 rpm. Current competition header technology is designed to actually pull air through (scavenge) the engine, using smaller primary tubes and properly sized merged collectors.

There are many factors that can help contribute to the performance of the competition engine. Overlap in the camshaft design plays an important role in how the header affects the characteristics of the competition engine. Today modern cylinder head design has led to less need for excessive overlap designed into the camshaft due to high flowing smaller intake ports. The current header technology now has an important role to help your competition engine reach its maximum efficiency.

Smaller primary tubes are used to keep the exhaust speed high in the header, which in turn, on overlap this exhaust speed is used to pull the air through the engine. Current header technology has proven that bigger is not always better on today's competition engine. Dyno results and track testing has shown that usually the best header combination is using the smallest size primary tube and merged collector throat. Track and Dyno testing has shown that you can literally choke a motor off by using too small of a header, and further testing has shown that you can hurt power and acceleration by using too large a header as well.

Primary tube size can be dictated by several factors in the modern competition engine. The engine cid, usable rpm, exhaust valve and port size, and horsepower of the engine are used to help determine the sizing of the header primary tube, length, and merged collector throat. Other important factors to consider in header design are the weight of the vehicle, where the engine is actually pulled down to on the shifts and how high the engine is spun at the finish. Consideration must be taken that a heavier vehicle will spend more time in the lower rpm range than a lighter vehicle, as will a race car with only a two speed transmission compared to a five speed clutch car. Primary tube length needs to be adjusted accordingly, as a shorter primary tubes tend to make more power in the higher rpm range and the longer tube is more powerful in the lower rpm range.

The merged collector is designed to pull air through (scavenge) the modern competition engine. The exhaust speed is kept very high in the collector, which in turn keeps the air moving through the primary tubes and literally sucks the air into the engine on overlap. This helps create the volumetric efficiency necessary to achieve the power results of today's competition engine. The merged throat size is mathematically determined using the primary tube size and horsepower of the engine, then can be slightly adjusted by using other factors in your racecars performance. As with the primary tube size you can literally choke an engine off using too small of a merged collector throat, and using to large of a throat slows the exhaust speed down in the collector, pulling less air through the competition engine.

Designing the competition header for today's modern race engine can throw the engine builder and the header fabricator for many curves. Each competition engine has its own inherit characteristics and when trying to reach the maximum potential, sometimes excessive trial and error is necessary with carburetion, camshaft, headers and many other components. Performance Welding Racing Headers has done extensive trial and error with many top competition engine builders to build you a competition header for maximum efficiency. Our competition headers are built using the widest radius tubing available creating a very smooth flowing primary tube for maximum power. Our merged collectors are mathematically sized along with extensive trial and error to create a header that will pull air (scavenge) through the competition race engine. Our craftsmanship, product quality, and attention to detail are absolutely second to none. Our competition headers have proven to be successful in NHRA drag racing, Bonneville, Winston West, Turbo, Nitrous, and Street applications.

Understanding today's competition header technology includes understanding today's modern competition racing engines. Performance Welding Racing Headers is constantly building competition headers in the four into one and Tri-Y design for our research and development program. We work closely with top competition engine builders, receiving header characteristic data on the dyno and racetrack, advising and receiving advice on future header designs to provide the fastest accelerating competition racing header in the industry.

- Mark Lelchook / Owner
Over the years we have seen that people make many, MANY mistakes involving headers. Mistakes are made due to many things - lack of common sense (or bad application of "common sense" because it is based on misunderstandings or assumptions), bad or inappropriate information or advice, decisions made on minimal information, ignorance, attitude (apathy), not willing to spend the money to do it right, etc. Here are JUST A FEW of the mistakes or assumptions we witness or hear about almost every day:

Bigger is better. This is absolutely the most committed mistake we see in headers - people buying headers TOO big - bigger than what is necessary for the engine to produce maximum performance and, because of that, reducing bottom end and mid-range power in the process. Depending how much oversize the header is, top end (peak) power can even be reduced! The only thing guaranteed when going to a larger header is reduced bottom end and mid-range performance.

Headers are NOT important.

ANY header is better than a manifold.

A more expensive header is a better header.

Header tube size is supposed to match the cylinder head's exhaust port size.

That there is one "correct" header tube size for certain engines. (455 Buick engine swap example.)

Equal Length is not important.

"GOOD" headers are not important for street use.

Confusion between Inside Diameter and Outside Diameters of Tubing.

Porting to match a gasket when porting should REALLY be done to match the ports in the header.

When should an exhaust port be left UNported?


We would like to present a point of view about headers that we don’t believe has ever been put forth in a magazine article — the possibility that any person — even in the garage behind his house — can build a header BETTER than any he might buy. No magazine would ever present this point of view as it would obviously offend all of its “header” advertisers as well as many others in the header industry. While there have been many articles written about header “building” over the years, they always seemed to be presented in the context “if you can’t buy something that will fit your vehicle, than this is what you can do”. These articles often presented a somewhat misleading discussion as they discussed only the construction side of headers but never seemed to present the POSITIVE side (or advantages) of what one might GAIN by building his own headers.

The advantages of one building his own headers are manifold (pun intended). Maximizing Performance is certainly one of them but preventing potential problems, personal satisfaction, obtaining exactly what one wants as a specific header design (or tube layout), etc. are other advantages to be considered as well.


If one just looks at what the header industry is basically providing most of its customers, maximizing performance no longer seems to be one of its concerns.

The descriptive term “Equal Length” cannot be applied to most headers. Tube and collector sizes are often selected more by “marketing types” to maximize sales — rather than maximize performance. “Bean counters” (accountant types) figure out that shorter headers are cheaper and easier to build so headers get shorter and shorter (so potential bottom end and mid-range power gains diminish or disappear). Optimum collector shaping — to maximize flow from the individual header tubes through the collector taper to the collector outlet — is basically ignored. Header port shapes are often more related to ease of header construction than the shape and size of an exhaust port in a cylinder head (often resulting in headers whose ports block exhaust flow to some degree).

Fellows buying headers are often buying what may be called “least worst” headers — not the best headers (because they can’t find them) but, instead, are buying headers that, in their opinion, have the least number of faults.

In contrast, fellows building their own headers don’t deal with others lack of concern or lack of availability — they just build what they want! Building your own headers allows you to end up with EVERYTHING you want and the only limitation on the outcome is self-imposed by your patience and skill.

Maximizing Performance

Maximizing Performance is accomplished through correct selection of a header’s performance design parameters. These are:

Tube Size;

Tube Length;

Collector Size;

Collector Length;

TRUE Equal Length header tube design;

Efficient Collector Shaping;

Efficient Port Matching.

TUBE and COLLECTOR SIZES. The header builder can select almost any tube and collector size he wants — for whatever purpose. The racer can pick the sizes that will give him the most power at high rpms or to accelerate the hardest off of a corner. The street user can pick the sizes that will produce the greatest overall power gains over the entire rpm range of use or to further maximize bottom end and mid-range performance (optimizing overall drivability, towing usage, gas mileage, etc.).

TUBE and COLLECTOR LENGTHS. The header builder can select almost any tube and collector length he wants — to maximize performance in whatever part of his engine’s rpm range he so desires. By building longer headers (tube lengths at least 34”) he can improve bottom and mid-range performance or by building shorter headers (tube lengths between 28-32”) he can emphasize top end power. In competition, with the collectors open, the header builder can pick the collector lengths that will maximize engine performance. (Even better, the header builder can setup his headers to allow EXPERIMENTATION with different collector extension lengths AND diameters to FURTHER improve performance.)

TRUE EQUAL LENGTH DESIGN. The header builder can actually control the overall accuracy of the tube lengths in his headers. If he wants the tube lengths to be exact, he spends the time to make them so. If absolute perfection is not important but performance still is, he can compromise a little on tube length accuracies yet still end up with an overall design much better than what he might buy. (We have helped thousands of fellows build headers over the years and many have told us they have been able to build, with minimal difficulty, headers with all tube lengths held to under a 4” range — from longest to shortest tube. While not a perfect header in tube length, one must also consider that over the years we have measured hundreds of sets of manufactured headers and have found very few that have tube length range errors that are under 4”. In fact, tube length errors of 8-12” (or more!!) seem to be normal(?) in headers manufactured at this time so the header builder who builds a header with 4” or less in tube length error is, by comparison, actually building a very good header — one MUCH BETTER than most headers being manufactured today.

EFFICIENT COLLECTOR SHAPING. The header builder can further optimize the performance characteristics of the headers he builds by selecting a collector “design” that is shaped efficiently to maximize flow from the individual header tubes through the tapered collector transition and then to the outlet.

There are three ways to maximize flow through a collector:

One, by selecting a collector whose inlet shape very accurately matches the outer shape of the header tubes that enter it (i.e., the collector must have very deep external creases), all exhaust gas expansion is controlled/minimized.

Two, by reshaping the header tubes — where they enter the collector — in the center by heating that area red-hot and forming the tubes into a cross pattern (+), the gas expansion and attendant excessive turbulence that occurs where the gases try to fill in the center area is essentially eliminated.


Heat center area RED HOT, then reshape into cross pattern. (We also hand-file all internal surfaces of this area to make sure that nothing obstructs exhaust flow.)


Three, by selecting a collector whose taper length is at least 4” or, even better, 5” long as opposed to designs that have taper lengths of 2 1/2” or shorter, the restrictive nature of the shorter taper is completely eliminated. (For what it's worth, the collector taper lengths - as short as 1" - to BE AVOIDED are typically found in block-hugger headers and shorty headers - types of headers that a lot of people are actually buying. Isn't this a good example of MANY PEOPLE DOING SOMETHING WRONG?)

To make this more clear, below are three drawings of collectors with various transition/taper lengths. From left to right: Very short taper (to be avoided as it restricts flow), Not As Bad, and Quite Good. Note that in this particular example the taper in the right most image is visibly LONGER than the width of the tubes entering it. This desirable header design characteristic is very easily seen in photos!



(most restrictive) (less restrictive) ( maximum flow)

Efficient Port Matching. The header builder can pick from whatever header flange designs he can find — port shapes and sizes, even different material thickness. If he has ported his heads or has aftermarket heads with different port shapes, sizes, and/or locations, he can grind the header flange ports to match. The header builder does NOT have to deal with headers whose ports are too small in some way, overlap the exhaust ports, and reduce exhaust flow!


Besides maximizing his vehicle’s performance, the header builder can also minimize or even prevent entirely a number of difficulties or problems that people often suffer through with manufactured headers.

To name a few:

(1) Tuning problems;

(2) Lack of performance gain;

(3) Poor header fit;

(4) Exhaust leaks;

(5) Spark plug accessibility issues;

(6) Melting spark plug wires;

(7) Ground clearance issues.

While NEVER mentioned in magazines, unequal length headers often create tuning problems due to their negative affect on air/fuel mixture distribution in the intake manifold. These problems often show up initially as part of a great disappointment with how the vehicle is performing and, later on, the realization that all of the attempts to retune the engine to make it perform better did not seem to work. The header builder avoids these problems by making the header tubes accurate in length.

Few people who buy manufactured headers ever get the full performance potential of their vehicle realized because the design of their headers never fully match the requirements of their engine as well as the intended usage of their vehicle. Some people who buy headers get no gain at all and some even lose performance because their headers represent such a design mismatch that they can’t beat the factory exhaust manifold! Unless he gets bad design advice, the header builder entirely avoids the possibility of having minimal or no performance gains from the headers he created.

While one can buy a header that will run through a starter, a frame, clutch linkage, etc., the header builder cannot build a header that badly as it is physically impossible for him to do so.

Because he can select the header flanges he wants (which includes their thickness), the header builder seldom experiences header leaks. If he does, this is more due to a craftsmanship problem than a design problem. But if he takes the time to grind the header flanges correctly (no weld beads left protruding above the flange surface causing the flange to bend) his headers won’t leak.

In the past, we’ve seen too many headers that offered such poor spark plug accessibility that we’ve wondered if the “designer” ever put the spark plugs in the head when he was figuring out the headers! But more recently we have seen entirely new spark plug accessibility problems come about because of design differences in aftermarket cylinder heads where the spark plugs are installed at different angles and/or locations. In some cases, the changes are so radical that there are NO headers that will work on these heads. The header builder shouldn’t have any of these accessibility issues as long as he has spark plugs in the heads during the construction process. He shouldn’t have any spark plug wire melting issues either (if he keeps that in mind as he builds his headers).

It is a fact of life that some headers hang too low under a car. Oftentimes this is due to designer error, but sometimes this is due to chassis problems that dictate that type of a design. The header builder can often reduce or prevent these problems from occurring by simply paying attention to them while he is building the headers.


One way that one can construct a header BETTER than a manufactured header is to externally braze the header tubes where they enter the header flange. Brass has a much higher thermal conductivity than steel so brazing causes the header tubes to be cooler nearer header flange which leads to longer header life. A side benefit is that the added brazing also makes the header noticeably quieter.

Another way that one can construct a header BETTER than a manufactured header is to use tube flanges wherever the header has to come apart to ease installation or go around some chassis part. Header manufacturers usually use slip-type connections when they design a header that must come apart because it is a cheap way of doing so plus assembly line construction difficulty is minimized. Unfortunately, slip-type connections often leak and then eventually rust together so the headers can become impossible to remove from the vehicle at a later date without destroying them. In contrast, the header builder can build his headers with tube flanges (and gaskets), enjoy a leak-free design and still take his headers apart years later!


While definitely a challenge, building one’s own headers can represent quite an accomplishment — leading to considerable satisfaction (as well as performance gained).


While many seem to feel that it is beyond their ability to build a GOOD header, the facts don’t back up that opinion. Right now some of the worst headers we’ve ever seen (too short, not equal length, collectors with extremely short tapers that are also poorly shaped, poor port match, etc.) are being sold. Building a much better header often means simply NOT repeating these same mistakes!

Another factor to consider is that we’ve been helping others build headers for over forty five years and, because of that, we feel that we are uniquely qualified to help others build better headers. (Look at our HEADER QUESTIONNAIRE to see how we can help you through our HEADER DESIGN ADVICE SERVICE!)

While there are a few companies that sell header parts, they usually sell whatever they use in their own headers. We are very much different than that as we offer many parts that we don’t even use but we know are needed. For example, we offer header flanges, for over 100 engines and cylinder heads with ALL flanges available with different port sizes and three different thickness. Many header flanges for more popular engines are even made available with different port shapes as well. We offer two styles of collectors—one style made by machine that is cheaper and another style that is made by hand but in over 200 varieties. We carry up to 10,000 mandrel bends IN STOCK from 1” OD through 4” OD for all types of header and exhaust system construction — so nobody is limited by not having the right bends to use. We also offer straight tubing, tube and collector flanges to match almost all of the tube sizes we carry, Oxygen sensors, bulk gasket material, etc.— one of the most complete selection of header parts around. PLUS—the BEST advice to minimize risk!


The Grumpy Grease Monkey mechanical engineer.
Staff member
4dr 57 said:
Here an interesting concept...make you own...only two thousand dollars!
That is what I did.
No one made true 'D' port headers to fit a GM 572/620 engine, much less anything that would fit in a '59 Corvette with custom frame and C4 suspension.
2" equal length primaries, 4" collector, 3" exhaust pipes. Cost much less than $2000, unless you consider my labor :)

looks like a really well though out and fabricated solution
one more in an endless list of reason that a serious garage tool list should include a decent quality 180-200 amp MIG or TIG welder

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The Grumpy Grease Monkey mechanical engineer.
Staff member
"Anyways, you pretty much told Mike he needed to get out and start learning how to fab his own headers and quit griping about the shelf stuff."

Thank you for explaining that. I've been interested in this hobby since I was a teenager over 50 years ago. I grew up in a time and place where men and boys were doing all kind of car related projects in their home garages. That imprinted on my brain the concept that it's all totally doable.

My own fabrication efforts started with very basic stuff with a lot of help from neighbors and the dads of my buddies. The short version of the story is that a lot of time is required to learn the more challenging skills like straightening body metal without bondo, machining and welding. But nothing matches the satisfaction of looking at the finished product and saying to one's self "I did that".
That feeling of satisfaction is not available from picking up the phone and ordering a "crate engine" or some bling from Summit.

Maybe that's an obsolete attitude. What do you think?

Ray W

there are times when changing header flange design, or using adapter header flanges, helps ease fit/clearance issues

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