Exhaust header

[sula]

I have '97 civic HB with d16y8 and now I'm planning to put used 4-2-1 header...

I would like to know your opinions about "home made" porting and polishing of exhaust header ? I've haerd so many opinions that I dont now what to do...

Some ppl says if I widen the ports it would be better for high RPM's and bad for low...
some says do not touch anything, some says wide the ports but DO NOT polish them...

So my question would be if is necessary to widen the ports, how much would it be ?
and is polishing necessary ?

tnx...

 

[reckedracing]

are you talking about the head side or the manifold side?

either one could benefit from a "port match"
thats where you take the gasket, lay it over the head or the manifold, draw lines around the insides of the port...
the area you drew on is extra material that you could do away with to allow it to flow better

necessary? no, but if you have free time it can't really hurt
polishing is a bit much for the manifold, and ok for the head if you do a good job...

people advise not to polish the intake side of the head too much cause the air is less turbulent and does not mix the fuel with the air properly...

if the head is NOT off the block then do not even consider porting, polishing, or doing anything else that will cause metal shavings to enter your engine...