ok well i have a b18a1 motor i'm puting together for my dd. and i'm eather looking at using my cast ls manifold or build a header. now i'm more then capable of fabricating and welding a tubular header together.

my main question is i have no clue the breathing needs of my motor and the last thing i need is to make a header that is to big, small etc...

now i'm not aking for build plans so to speak ( not that i would expect that or want that). but i'm more looking for a good start to work off of.

specs:
81mm b18a1 w/ pr3 pistons, (11.4:1)< zeal auto comp. calculator, stock head/cams, modded gsr intake manifold/t body, stock gsr intake, and a 2.5" header back exhaust.

only thing i will be getting in the future will be a set of crower 404's and valvetrain.

ok guys lmk what you think

 

anybody???

 

seriously there used to be ppl who helped answer questions....

 

If you actually want to make power out of a non-vtec B18 (which can be an uphill battle), then I would seriously leave the the header to the professionals, who makes the things for a living.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gibsanez &raquo;</TD></TR><TR><TD CLASS="quote">If you actually want to make power out of a non-vtec B18 (which can be an uphill battle), then I would seriously leave the the header to the professionals, who makes the things for a living. </TD></TR></TABLE>

well i know im not going to master making n/a headers over night here ppl.
but i'm more then capable of making a header as i make turbo manifolds and related peices daily, it is my job. with that said it is pretty hard for me to spend $600-1000 on a custom header from one of the known companies, when i know i can do similer work for cost of matarial and my time.

so with that said i'm not looking for a step by step diy. i just want to know where to start, like tube size and legnth for primary and secondary. i can figure out the rest from that.

also what would be a better layout 4-1 or 4-2-1?

 

anyone????

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 91jdmhatchback &raquo;</TD></TR><TR><TD CLASS="quote">
also what would be a better layout 4-1 or 4-2-1?
</TD></TR></TABLE>

In theory, the 4-2-1 headers should make more torque, at the expense of some top end, but in real life, you are not going to see the advantage of that design on a motor like that. They work great on V8s, but small motors make power by reving and 4-1 headers make more power at higher rpms. Yes, I know its an LS, not a B16, but it is still a small motor in the overall scheme of things. Go with a 4-1.

As for the tube diameter - you must know someone with a decent header; throw a caliper on there and see what the pipe diameter is.

My .02.

Best of luck with your project.

EDIT --&gt; if you do go with a 4-2-1, copy the HyTech layout which makes the 'Y' really looooong. Again, small motors rev to make power and they like the long tube exhausts.


Modified by Top Ramen at 10:09 PM 5/30/2008

 

thanks ramen...

yeah i thought about measureing tube diameter. but primary and secondary length is what i'm stuck on.