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Discussion Starter · #1 · Flanges.htm

Ive tried to stay out of this but I might as well jump in and get involved Ive done this many times its not that hard. heres what I do, get some of that plastic smurf tubeing in the 2" dia size and some ceiling hanger wire and some of that hard set constuction 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 tubeing 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 startin with the upper inside collector position and the rear exhaust port, bend and fit the smurf tubeing 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 tubeing,(or have your local muffler shop duplicate it) this method REALLY makes the fit and try time minimal. and assures equal length tube headers.SMURF TUBE is flexable plastic electrical conduit thats normally BLUE or ORANGE and COMMONLY called smurf tubeing by contractors its a plastic version of that metal GREENFIELD tubeing 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 les you will need (3)BTW the 4-6 wires act like rebar in concrete, the loops keep the wires from moveing in the foam while their incased 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, or you need headers for a LS1 in you 67 camaroHERES INFO YOU CAN USE
heres a quick way to figure your true primairy tube length (use 1250f degs(950k) and 5000rpm for race cars, 1200 degs(922K) and 3000rpm for street cars ) if you want other temps look here
heres a quick cross check
or if your really lazy

and the answers in meters (about39"=1 meter)
but if you just use 36"-40" it will just move your tuned rpm level up or down slightly, not enough to make much differance except on a very peaky engine combo in a very light car.and this assumes your tube dia. is the same size as your exhaust port size.(never smaller, slightly larger dia. is ok)
btw mild steel is much easier to work with than stainless
the pipes should be slightly oversized rather than so small that they partially block the exhaust port.
a pipe dia. that is small enought to partly block the exhaust port can hurt the cylinder scavageing by causeing turbulance and restrictions at the port exit, while a primary tube size slightly larger than the port leaves a ledge that partly retards returning pressure waves from reduceing the scavageing effect,...USE THE CALCULATOR PROGRAMS THATS WHAT THEY ARE THERE FORand keep in mind the displacement and rpm levels effect the dia. and length of both the primaries and collectors, these MUST VARY IN DIA. and LENGTH TO MATCH THE ENGINES EXHAUST PULSE TIMEING so that a NEGATIVE PRESSURE WAVE WILL BE CORRECTLY TIMED to SCAVAGE THE CYLINDERS EFFICIENTLY at the desired rpm range
if you want other temps look here heres a quick cross check (
(btw its not((Degrees ATDC)they mean subtract the BBDC from 180 degs. then use the answer and the rpm level should be picked for the expected torque peak [
or if your really lazy
and the answers in meters (about 39"=1 meter
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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