Tips on how to make Extractors/Headers

[darrenwilson]

I'm looking for tips on how to make extractors for A15 the motor is stock,i'm also leaving it so for a while.First time getting 1 i haven't got any showed up for sale so i have to make 1 and i dont kno what specs to make them at could you guys help me out

[darrenwilson]

Any tips fellas

[z18et1200coupe]

Make sure your able to get the manifold bolts on haha. Just give it a go. go buy a bunch of 90 and 45 bends and cut loose!

[nick_m]

There is heaps to it, but yeah the best way is to just get into it
have a read through this, they have some other good articles
http://www.burnsstainless.com/construction.aspx" onclick="window.open(this.href);return false;
for length make them about 35-40" long, the longer they are the more torque. Use 1 3/8" primaries and buy a 4-1 collector with a 1.75" outlet, of you exhaust is bigger than that step it out after the end of the collector, dont just open the collector up to exahust size, keep that taper down to 1.75" to then taper it back out to exhaust size. Too big a collector outlet KILLS torque. Always err on the smaller side with exhaust stuff.
There is heaps to exhaust design but if you started around those specs you wouldnt be too unhappy
As far as construction goes, take your time be fussy and get the fit up between pipe joins spot on. It means when you weld it up you are less likely to have problems with the flanges bending or pipes moving around where they arent meant too etc.

[nzdatman]

Hey nick I'm building some headers for my L20B, pretty much stock with dellortos at this stage, have run 2-1/2" pipe to the resonator then steps down after that, using a coby collector 1-5/8" primaries with 2" outlet, was going to cut the collector back where the 2-1/2" pipe meets, do you think that's too big? Hopefully you see this soon I want to weld it all up today.
Should have gone 2-1/4" all the way through I think but I used what I had to get it done quickly.

[Zeeya]

to better understand what you want out of it you have to ask yourself a few questions first.

how much power are you putting out?
how are you going to be driving the car? (what rev rang?)
or do you just want the car to sounds good with better gas millage?

as said above, longer primaries will get lower to mid range torque. have a read up and find out what length will work best with your motor/setup also have a look at how much room you have with ground clearances when it comes to putting a collector on.
Are you going to put a flange alittle after your collector? might be a good idea if you arnt happy with the size or sound of the rest of your exhaust system, at these this way you can unbolt it and change it rather than cutting and rewelding.

as nick said, be fussy with your fittment. take your time, the more you put into your prep work the easier the welding will be and less gaps means less distortion and less movement in your pipes. Put a a brace between your pipes up by the head and one further down by the collector to stop it from twisting with the heat.

all you are doing in increasing the airflow through your motor ( letting it breath better ) in saying this you dont want to get to big on your primaries or to be after your collector, theres a chance you could be taking power away from the motor if you go to big.