Quicktripp3

First off

Hello and forgive me if this is a stupid question?

I have a 13b in a sandrail i am in the process of finishing

I am in the process of making my own header and i have to ask if i can enlarge the flange exhaust holes or keep these the same size as the stock exhaust manifold i would have to assume they are smaller than the exhaust port on the block for back pressure?

Also what size tube do these motors like 1.5? and what length any change if it is shorter or longer in hp or torque?

Confused in Mi thanks?

sandrags only 300 ft if that matters

Danno

Basically it seems that you want to port the exhaust ports. This should not be a problem as long as your new "header" matches up well. You shouldn't have to worry about the back pressure at the point of exhuast gases exiting housings, It would be the back pressure created by your exhaust that would be some what important. I had a 3" exhaust off the turbos so I really did not have a whole lot of back pressure and the car ran great. For your tube sizre you could try and find some aftermarket parts to see what they use. Good luck.

Mr. Midas

Hey,

Your project sounds pretty cool. 2" od for primary tubes seems to be working great for me. For my header I came up with a design that afforded longer and more equal primary tubes than most. First I made commonly available bend pieces and went with measurements taken from clearances in the vehicle to line them up at the correct angles. It sounds more complicated than it is. You could experiment with a CAD program or just use some cheap tube to mock it up the way you want it.



Everything was stainless steel and I made my own 2-1 collector /resonator with a slip-fit end(that is 2 @ 2"od into 1 @ 2.5"od with 3"od resonator chamber in between). With a square, compass, and protractor a simple jig was used to accurately mark out bend angles to cut. I used two, 2"od "J-bends", a couple reducers, a couple short pieces of 3" and 2.5" strait pipe , some O2 bungs, a flange from Mazdatrix, and some old wood for a jig. I got it lined up and tacked it together. After three or four test fitting adjustments, I bartered with a friend to TIG it all up. With simple calculations I determined this header should provide maximum benefits beginning around 6600 IIRC. My motor still retains virtually stock ports... just smoothed out and velocity matched.







Many people cut out the diffusers in the exhaust sleeves (or get turbo housings.) and blend the housing port shape out to match the diffuser. Look here After polishing those sleeves I ended up welding in a roof to reduce the extreme flare and turbulence caused by their mini megaphone shape.

[attachment=44188SCF0474.JPG]

With the 2" tube it's very close to a perfect transition, and the roof of the port makes it D shaped and impedes revers pressure waves better.







I still need to throw on some header wrap and a heat shield to cut down on underhood temps.

I just realized i don't have any finished pics... I'll have to get some after I remove it for wrapping.







[attachment=44186:Header_assy_7.png]



[attachment=44187SCF1378.JPG]





Hope that helps for ideas. I didn't write a whole lot down when I came up with my design. I'll have to get the details off the program i used.

I'd stick with 2"od primaries, and longer(aprx. 22+" long each leg) for stock ports /lower power band if thats what you have. If its a true dual tube setup, a couple resonators placed in the right place will help power too.



I'm no pro though, so keep doing your research. You're on the right track. I'm sure others with more experience will chime in. There might be some stuff in the archives too.



Good luck!

1Revvin7

Primary tube sizing depends on a lot of things.



O.D size is only half the equation, you've got to consider what size wall thickness to determine the entire picture. I would start with 2" O.D. .65" wall tubing and go from there unless this is a bridge or p-port engine for a drag only vehicle.

Quicktripp3

Thank you

I ended up with 2.5 inch o.d. tubes and 23inches long no merge yet?

or should i just put resonators on it ?

heres a link tell me what you think be honest

or what you think or if you think it will perform.

and i am having a new problem raw out of the pipes

if i turn on the fuel pump it drowns the motor regulator or inj or?

thanks again Randy

http://s151.photobucket.com/albums/s160/Qu...urrent=b017.flv

Mr. Midas

That's thing is the BOMB!



Try to match tube lengths if you have room. I'd put a collector resonator with a megaphone on the end. Angled upwards of course!



[attachment=44195:Megaphone.jpg]











I finally got my header off so I can wrap it up. I really forgot how long I made it. 30+ inch primary tubes!