How do headers work?

[Guest]

Ok, I know they bolt on and carry exhaust from the manifolds to the rear of the bike.

More specifically though...

What makes a header a header?

How is a 4 into 1 header different than a 2 into 1 exhaust... and are there not 2 into 1 headers... like for 2 cylinder engines? Is there a 4 into 1 exhaust that is not a header?

I'm wondering about down the road when my mufflers finally fail and I need new ones... maybe a different set up or header would be worth consideration.

And can headers work on bikes with stock air boxes.. or must they all be modded?

[tom203]

Did you visit wiki? decent exhaust tuning is an art.

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=7&ved=0CHgQFjAG&url=http%3A%2F%2Fen.wikipedia.org%2Fwiki%2FExhaust_manifold&ei=EaAmUJ3HK4L30gG0j4GgDA&usg=AFQjCNE_epe-w30Hxh7A8rwmYxycKJMnvQ&sig2=sAjDHsDqvyvCSCkXAngJAg

[twotimeGSr]

Thanks Tom,

That was a great read. It seems like by the definition in Wiki that our stock bikes came with stock headers... maybe just not what we might know as headers because they are 4 into 2 headers... not 4 into 1's.

[Blastr2783]

What headers should do is allow for more efficient exhaust. And combined with proper carb jetting or injection tuning they do. A motor is at it base an air pump, and in order to get more air and fuel in you have to get essentially the same volume out. Most modern exhaust systems are about as good as it gets but older stuff tended to be more restrictive than necessary and could benefit from the proper jet/header combination.

[twotimeGSr]

So as a rule of thumb... does anyone know what our bikes were set up in the factory with as a percentage of performance? Is my stock 79 850 maybe 85% or 98% of what it might be if modded with a different (more tuned) exhaust with jetting.

And.. let's say I put on a better tuned exhaust and re-jetted... Would this help fuel economy if I drove the same way... or is this type mod only really good for obtaining more power?

[SVSooke]

The truth seldom stated is most 4>1's actually decrease HP with no other mods.Emphasis on most because a few will increase HP but even then not really enough to make a real difference on the street.The + on the street for the 4>1 is the fact they are much lighter than the stock exhausts.