I have done quite a bit of research and found conflicting information - hopefully someone here can help.

I purchased a turbo manifold for my D16 and noticed that the openings for the runners are quite a bit larger than my exhaust port openings on my head - likewise the gasket is much larger.

Some sources say that it is not good to enlarge the exhaust port becuase you will lose bottem end/mid range performance. It seems to me that i would want to at least inlarge the exhaust port to match the manifold?

Is my thinking correct here?

 

humm....proven fact, port matching performs better. will it hurt that your ports arent matched? no. so you take that info for what its worth.

www.theoldone.com has alot of good info when it comes to porting.

 

Thanks for the post. I've spent a lot of time on endyne's site which is what brought the question up to begin with.

Most of the articles that are posted on thier site deal with NA applications. After talking to the machine shop that did some of my basic work they think opening the exhaust ports is an absolute must, i.e. "get the gases out as fast as you can".

All of the other sources that I have read talk about the exact science of head porting and the need for balance.

I'm trying to learn more than anything - and I'm trying to do as much of the labor as possible on my own.

I've already openend the exhaust ports up to match the manifold - and it looks pretty good. I just don't want to put to much more labor into it and find out I've went down the wrong path.

Time is money.

Thanks

 

I followed this.

http://www.honda-tech.com/zerothread?id=446708

 

porting the head rarely hurts performance.ive found quiet the opposite to be true. exhuas runner porting usaully improve low end as long as it doesnt exceed 75% of the intake flow. with the proper cam it would work bette at a higher % but youd need a different cam

 

its always a matter of velocity. depends on how big it actually is. corky bell says whenever given the choice, go with the slightly smaller tube size to keep gas velocities high.
for the exhaust, you want the manifold slightly larger than the port for anti-reversion.