Custom Header Specs / Design

[Muad'Dib]

I have a local shop here in town that will build a custom header. I was thinking of having them build one very similar to the borla 17020 since its no longer available. Possibly adding another o2 bung (for a wideband) and change the collector to 2.5" (if it isnt on the borla).

Here is the specs they need:

Primary Tube Size Desired (1.50", 1.75" or 2.00"):

Head Flange Thickness (5/16", 3/8" or 1/2"):

Material (Mild Steel or Stainless):

I know the material is Stainless, and im pretty sure the Head flange is 3/8", but i have no clue what size primarys the Borla 17020 has... Does anyone know?


Also, since this place can build a custom header, would there be a better design to have them make? Right now im just seeing what they can quote... if they can do it for a decent price (id say around the price of a borla $550 or so) i might go for it.


Any suggestions?

[Flash]

For $40 you could design you header to perform in any rpm range you choose!
http://www.maxracesoftware.com/pipemax36xp2.htm


Flash

[crustodd]

Hey Chris,
What shop is it? I talked to a guy in Bend who does mandrel bending, but he wanted $900.00 for a 2 1/2" header to tailpipe, in stainless, with a Flowmaster. Seemed a bit steep. Wonder if it's the same shop? Did you pick up the Dana 44?

T~

[Muad'Dib]

No i didnt get a 44... Im not sure if i will or not. Everything is so up in the air.

I dont think this is the same shop. This shop does do mandrel bending, but the last time they quoted me for a custom exhaust system from the header back stainless with high flow cat and high flow muffler it was about $500. Its Custom Exhaust Specialities. http://www.4customexhaust.com/



No one has any ideas on a header?

[5-90]

Head flange is easy - measure existing.

The second bung for the WHEGO I like - I wanted to do something similar anyhow.

There is a forumal for determining optimax primary ID and length for torque peak - I'll have to find my copy of _Scientific Design of Intake and Exhaust Systems_ or the _Bosch Handbook_ to dig it up (and I haven't forgotten about your high-current modular connectors, either. Still beating the bushes on that one.)

Are you going to spec an "equal length" header - all primaries the same length?

I just figure if you're going to spec the whole thing from scratch, why reinvent the wheel? Borla does a good job, but you've got an opportunity for a "clean sheet" buildup here, and I think you should take it!

[1bolt]

Pipemax (see flash's link) does that based on those very same scientific design principles in the books you mention among others.

Equal length is not that important, total average primary length will be far more beneficial for tuning the power band of a street/offroad build where improving peak torque at 2000-4000 RPM's is far more important than improving peak horse power at 4700 RPM's. So if you can fit 6 16 inch primaries of the same length, or 3 @ 24" and 3 @ 16" which comes to 96" total inches of primary length versus 120", which works out to 16" average and 20" average. The longer primary will improve scavenging more and more as the length increases. So ANY length increase is worthwhile as long as the total average increases.

The well known Borla "long tube" is actually pretty far from being a real "long tube" header, it's a Tri-Y header and is probably one of the the best off the shelf high quality headers for a 4.0 or stroker, but it can be improved on a lot.

[Jeep4xb4u]

I like this idea ok Im lost

Have i over looked somthing? Is this the same part number that used to also be specd out for the Renix system from Borla? There is vurtually no header that is designed for the 2686 head now other than Pace Setter i know this isnt the most common head choice for these builds but there is atleast one poor guy using it (me). Will other years of headers work on my lower port designed head? Is it just a matter of EGR and heat riser flagges that keeps them from being listed back to those years?

Im only confused because Muad's got a 90' cherokee and that borla part number says it only fits 91-92 manche's

[Muad'Dib]

Im going to be using a 7120 head for the stroker... so the 91-95 header will fit right up. I think the 87-90 borla is part number 17010.

[5-90]

Pipemax (see flash's link) does that based on those very same scientific design principles in the books you mention among others.

I'd kinda figured it would - but it's forty bucks to automate maths you can do yourself (unless it does quite a few other things.)

[Flash]

Pipemax (see flash's link) does that based on those very same scientific design principles in the books you mention among others.

I'd kinda figured it would - but it's forty bucks to automate maths you can do yourself (unless it does quite a few other things.)

I have his pipemax software(also have his" FREE" ET. Analyst for predicting 1/4 mile times) but haven't had a chance to play around with it much yet.

I hope Max don't mine, but this is a statement he makes in the instructions of PipeMax

PipeMax is primarily a Header Design Program with extra FREEBIE calculations
and lacks enough Inputs to make it a full-blown Engine Simulation Program .
Some of the Inputs will make little or no difference in predicted HP and TQ
but all of the Inputs are needed to predict the correct Intake and Exhaust
System Lengths, Diameters, and Areas.



Flash.

[ccpanel]

Pipemax (see flash's link) does that based on those very same scientific design principles in the books you mention among others.

Equal length is not that important, total average primary length will be far more beneficial for tuning the power band of a street/offroad build where improving peak torque at 2000-4000 RPM's is far more important than improving peak horse power at 4700 RPM's. So if you can fit 6 16 inch primaries of the same length, or 3 @ 24" and 3 @ 16" which comes to 96" total inches of primary length versus 120", which works out to 16" average and 20" average. The longer primary will improve scavenging more and more as the length increases. So ANY length increase is worthwhile as long as the total average increases.

The well known Borla "long tube" is actually pretty far from being a real "long tube" header, it's a Tri-Y header and is probably one of the the best off the shelf high quality headers for a 4.0 or stroker, but it can be improved on a lot.

revive old thread.
is there any advantage while making a custom header to group matched cylinders together in a 6-2-1?
IE;
put 1/5/3 together and 6/2/4 together then join the go to single?
thanks
Mark

[SIXPAK]

Groupings are done 1,2,3 and 4,5,6. Using this senario look at the numbers to the right and follow the firing order. Following your suggested pairings does not allow proper scavenging between cylinders.

[mendelmax]

Guys, I have one serious doubt in designing my header- I suffer from serious lack of knowledge on this ground

To achieve proper wave tuning I have found, that optimal length for second wave deflection in my engine is 140 cm =56".

Now for sure this is far too long to fit under the rig, so I decided I will try to make it for fourth wave deflection, which will then give me 70 cm primaries = 28".


The thing is, that with aftermarket 6 => 2 => 1 design, I usually see, that the primary pipes are +/- equal length and quite long, and then, the secondary pipe is very short. To me it seems, that to prevent waves from interfering, the secondary pipe should be exactly the length of the primary + port length. In other words, in my case it would seem, that I would need six 28" long pipes, gathering into two banks, and then two approx. 30" long pipes, that will gather into one, going to the muffler.

Am I right, or am I missing something? Or is it really acceptable to just fit any length secondaries?

[Cheromaniac]

I know the material is Stainless, and im pretty sure the Head flange is 3/8", but i have no clue what size primarys the Borla 17020 has... Does anyone know?

Yes. The primaries are 1.5", the secondaries are 2", and the collector is 2.25". I had the collector of my Borla header upsized to 3" and I have a custom 3" downpipe. This is how my exhaust looks:

http://www.angelfire.com/my/fan/Exhaust.html

..and this is a Borla header right out of the box with its 2.25" downpipe:

[ccpanel]

Groupings are done 1,2,3 and 4,5,6. Using this scenario look at the numbers to the right and follow the firing order. Following your suggested pairings does not allow proper scavenging between cylinders.

my suggestion was more of an example and less of a idea.

i see them 123/456 all the time and wondered if it was the best scavenge or just lazy/easy manufacture.

i didnt see anything to the right and didnt understand you about following the firing order. just another example of me trying hard to learn and all you group members doing an excellent job of steering me straight.
I truly thank you!
Mark