Headers help!

[Trailblazin]

Ok here it is, know a place that does custom headers, thinking about doing one for my ride very soon. Only problem is that my car will be their first so im kinda worried, anyway spoke to a friend of mine who's into tuning big and he told me the best bet for the header would be

"1 5/8 inch primary tubes and 2.5 or 3 inch collectors..just make sure the primarys are 1 5/8 of an inch".

Does this sound any good?? If you guys have any other suggestions plzzz let me know. I would love to see just how much an increase I could get from this. If it happens, I will dyno the car before and after and see the gains. If they're big then I can export some from you guys in the states. Ideas plzzz

[iDontKnow]

Excerpt from Burns Stainless: http://www.burnsstainless.com/TechArticles/Theory/theory.html

There are many ideas about header pipe sizing. Usually the primary pipe sizing is related to exhaust valve and port size. Header pipe length is dependent on wave tuning (or lack of it). Typically, longer pipes tune for lower r.p.m. power and the shorter pipes favor high r.p.m. power. The collector package is dependent on the number of cylinders, the engine configuration (V-8, inline 6, etc.), firing order and the basic design objectives (interference or independence). The collector outlet size is determined by primary pipe size and exhaust cam timing.


I dont think there is a definite answer... the best design will probably come through trial and error... and from what your performance wants are.

But I hope you're planning on making them true duals!!

[Trailblazin]

cool man thanks for the reply, i took a look over it and i think im gonna email them with my specs and see the advice they get me. btw we can't get true duals as we only have one header, but maybe we could fabricate something into 2 connecting points for the 6 manifold outlets and create true duals from there....i dunno, i'll look into it and keep u posted....

btw has anyone seen any pictures of our header?? ive been trying to look for them on gmpartsdirect.com but no luck.... :confused:

[iDontKnow]

The firing order for the I-6 is 1-5-3-6-2-4.

For true dual, you'll have to use two collectors, and will probably want to run cylinders 1, 2, 3, into the same collector, and then 4, 5, 6 into the same collector. This should give you the most consistent results for scavenging. At least thats my thoughts... someone feel free to prove me wrong about this.

And just a few things to keep in mind...
The bigger the exhaust pipe, the more volume is allowed for the exhaust to cool, slow down and get heavy, which can negatively effect scavenging results.... but on the opposite hand, too restrictive of an exhaust can ruin the scavenging flow.

Also, running headers, especially with dual exhaust, could impact what the O2 sensor outputs back to the computer... which could effect your air/fuel ratio... which could cause the engine to run too rich or too lean.

Thats all I can think of for now... hope that helps!

[Envoy Fan]

Thought the 4.2L I-6 actually needed some backpressure to operate correctly :undecided

If one were to go true duals, sounds like the old split manifold of the 1950 -60 era. Also would need two cats to be legal, if the project got this far.

[ScarabEpic22]

Thought the 4.2L I-6 actually needed some backpressure to operate correctly :undecided

If one were to go true duals, sounds like the old split manifold of the 1950 -60 era. Also would need two cats to be legal, if the project got this far.
I agree with Bill, the I6 engine needs backpressure to work correctly.
As for the exhaust, Bill, remember he is in Kuwait and there arent any emissions there. But, if it was to be exported to us here in the states, there would need to be the proper number of cats installed.

[Trailblazin]

well finally made a move at looking into this... hopefully this'll be my blazers xmas prezzie :D about the O2 sensors, I know that cars that have true duals have sensors on each side of the pipes, I want to do this, but im not sure if I can, like would i need to program the ecu to read from both sensors? or would i just attach both of them to the one wire?? Also, if I just plugged one exhaust pipe, would I run too rich or too lean??? I mean right now I have nothing blocking the exhaust exiting the car. All cats are out, there's only 3 mufflers (Straight through design) and I never got any engine lights thank god, so Im thinking i might just leave it as one.

I will be making these true duals, and found a header from an inline6 supra to help me out.....here's a pic of what it should look like hopefully, i will deffinately get this dynoed before and after, and if it installs smoothly, i'll get the guy here to do more if anyone else is interested..bout the cats, might want to buy a magnaflow high flow cat if you need to do ur emissions. Can also get that a great prices.

Anyway, if anyone has any ideas about the O2 sensors, plz let me know. cheers

here's a pic of the header
http://www.trendgear.net/auto/86-92_toyota_supra_NT_header_obx_10363.jpg

[Trailblazin]

1st stage in process. bought the manifold gasket, went to a couple jetcutting companies round here to get the shaped cut out into 10mm thick metal. Not sure which one to chose yet, they say iron is the best bet as its not as expensive, but im thinking i will be using stainless-steel.....

talked to the mechanic at babil (place where they'll be doing them) told me some news i didnt want to hear, they didnt have 3/4" pipings which would be perfect, so they reccomended i use 7/8" piping. This would, I'm sure, make me lose allll backpressure. So looking into a place where they can offer me 3/4".

Once the gasket covers done, will take some pics....(this will be a slow process as money is limited) then will be the task of finding the right sized pipes.

Another set-back is the collectors, found some on summit but they are back ordered till the beginning of next month. These are 3 into 1 with the collector size being 2.5". Once I get them, they should be perfect for the headers.

until then!

[geneelder]

Instead of buying collectors, have the company that is making your header custom make the collector. If they can build a custom header, they can surely make the pipes collect with cutting and welding.

[iDontKnow]

This is the GM part number for the exhaust manifold gasket: 88890561

For a good seal with your headers, you'll want to replace the old gasket.

Oh, and I'm assuming the "manifold gasket" you're having made is actually the header flange that you'll be welding the runners to.

Hope this helps!

[geneelder]

I think he is using the manifold gasket to have a header flange cut with a flowjet

[Trailblazin]

ok just to edit what i said above since i can't edit it above, with the primary tubes i want 1 3/4" but they can only offer me 1 7/8".

Yeah the gasket i will be making is the header flange, couldn't think of the word when i was writing the post.

not too sure about the part number, i just walked into the spare parts store and told them what I wanted. Cost me $15, worth it i think. I did want to buy the manifold but itd cost me around $200, so gonna go to the scrap yard and see if there are any cracked ones laying around to get an idea of the proper size.

i would want them to make the collectors for me, the only problem is they want to do it their way, they've never done a header for a chevy inline6 before so i'm kinda worried they'll mess it up. They normally deal with F-bodys, Mustangs, Trucks, all 8 cylinder vehicles...will go in there tmrw and see what they can do bout the pipe sizing. If not I might have to order some from the states. Another $100 on shipping!!!

[Trailblazin]

http://www.q8speed.com/upload/uploaded/13122005(001).jpg

:raspberry

[iDontKnow]

Nice! Have you decided what length you're gonna make the primary tubes?

[Trailblazin]

no not yet, they told me that since I was their first GM inline6 project that they'd do a prototype first then work on mine. Hopefully from that we'll be able to determine whats wrong, I will be taking a DYNO run soon just to see how much HP Im pushing, then once the prototypes are finished take another one and see what area needs improvement. Im really hoping that I actually gain torque in the lower regions.

Will keep informed soon as it happens.

[Trailblazin]

ok well talked to the mechanic a couple times since I gave him the manifold gasket and stainless steel. Should have the flange ready by tmrw, will take some pics of it once its done. He was saying we should be aiming around 17" to 22" for the primary tube lengths.

The reason there is a 5" difference is because there isn't that much space for us to work around with. So if the prototype fits perfect with 22" primaries, then that will be final. If not then we will cut about an inch of each time until it does. This is the prototype so we are allowed to mishandle it if it causes us any grief :p

Anyway, Im getting a Jet chip this tuesday/wednesday thanks to fish hunter, once its installed, ill take a dyno run of my motor now and then one with the header..

Hopefully will get 330-340bhp in gains with all the mods Ill add soon. This is around a 50-60hp increase with just basic upgrades. Wishful thinking i know, but i want to stop that BMW 325 gaining on me once I hit 165kph!! :yes:

[Trailblazin]

finally got the flange done, will be getting it all chromed up before the work. only prblem now is the main mechanic has gone on holiday and won't be back for a month. so no more work for the month. 8mm thick, stainless steel

http://www.q8speed.com/upload/uploaded/26122005(001).jpg

http://www.q8speed.com/upload/uploaded/26122005(003).jpg

[glfredrick]

An old time drag racer trick to determine the correct primary length was to hook up the tubes (long) without a collecter, paint them with spray paint, then look for where the paint burned off. That was the place to stick the collecter. I don't know how that might work with a TB, but trial and error will help get the first set of headers right.

I'd also proably err on the side of too-small primaries than too large. The large ones are for wide-open throttle flow only, and tend to rob torque on the low end for street use. An alternative is to use stepped tubes (larger as they progress toward the collectors). Anti-reversion techniques (ala Flow Tech) can also add in retaining low end torque, which the I-6 is short on to begin with (or so it seems with that silly torque-limited start system they have in place).

[Trailblazin]

well i've finally decided on a pruimary size which is 1.5". The reason being I took a look at the Hedman header dimensions and they have showed 1.5" for the primaries, Im sure they've done way more research into this then I have, so i'd rather stick to the pros. The garage I'm working with has no idea how to even measure flow. So hopefully this'll be the best diametre. About the primaries, they will be doing a prototype out of aluminized, i could ask them to keep it my ride, spray paint it, and then see where the paint burns. But would this dirty my engine bay :(

please any more info you can give let me know, I am a complete ametuer so whatever input you guys give me will be well taken in. I don't wanna screw my machine up just yet, i need to wait at least another year till i can :p

[IceN]

are they gona be equal length

[glfredrick]

The headers won't screw up anything, even if they don't maximize the exhaust. They can't be much worse than the factory setup run on 99% of all vehicles, which is mostly designed to be a handy, quiet outlet for exhaust gas with no real demand for performance. About the only thing you could do wrong is to make them too large, which will kill your flow rates. You want to think along the lines of max flow speed at the RPM's that your truck uses, and to get those max speeds, you need the power of suction (I'm using this word to simplfy matters). You get "suction" when the other cylinders help to scavange the exhaust from the port that is currently firing. In other words, when one cylinder fires, it sends a pulse of exhaust gas out, and behind that pulse is a vacuum. That vacuum pulls the next cylinder behind it, which in turn... you get it. This allows for the most power unless and until it scavenges so good that you end up sucking the mixture out of cylinder before it is burned, which you probably will not do with the valve timing on the I-6. (That is for huge overlap valve timing like on dragesters!)

IMO 1.5" primaries would be just about right for the displacement of the I-6.

[Trailblazin]

are they gona be equal length

thats what i'm aiming for, i'll be on the mechanics head when he's doing them so i know exactly whats happening. He did tell me that maybe one or two primaries might be a bit longer then the others, this is only so they can all fit in the collector right.

well 1.5" it is, i may as well go down the shop and start talking to the other mechanics and see if maybe they might be able to do a prototype out of aluminized for me.

[z-ya]

Cylinder displacement on these engines equals a 5.59 liter v8 so I
would size the primaries accordingly. Plus these are 4 valve engines
with large exhaust ports as shown by the gasket.1 5/8 x 30 inch
primaries is where I would start. Make a short adapter to smoothly
merge the primary tubes to the oval port entrance. Good luck with
this.

[sk_trailblaz]

Trailblazin', have you had any success on having your custom header built yet? :)

[Trailblazin]

no im actually still waiting for the mechanic to come bakc from hajj... he should be here in the next week or so...not to worry, pics and updates will be posted soon as he starts them..