Also refer to the article on www.prelude3g.com. He talks a little bit about this under his "n/a build up" article. I believe he didn't gain much from his head work. But that doesn't necessarily mean that you wont have success with it. Good luck if you decide to go this route.
port matching will always make a difference, no matter what car it is.
in our cars though, from my experience and research, the porting of the runners and ports themselves doesnt really give you much more power unless you have a turbo or supercharger. it does shift the power curve over a little though towards slightly higher rpms. the polishing part is what will give slightly better performance though. not a lot, but a few hp. our heads and mani's are already pretty much set up perfect for higher end power. they just need the rest of the motor to be tuned for that higher rpm. ie: cams, exhaust, compression, timing.
the key to our mani's and heads is to not remove much metal. the ports/runners are already a pretty good size, they just need to be smoothed out from the casting and its flaws. most people make the mistake of enlargening the ports/runners too much which gives higher flow ratings, but lower velocity, which in combination does nothing noticeable for a power increase.
the only way you really will notice much gains from porting is if you get cams to match the rpm the runners are tuned for, and if you have forced induction.
when i speak of rpm tuned for, search yahoo or google for things like port size calculator, runner calculator, stuff like that, and you'll find all sorts of goodies on sizes for specific rpm tuning. but the key is to match all aspects of the motor for that rpm. for example, if you port the intake and head for say 5800 rpms, and the exhaust is tuned for 4500 rpm, and cams are for 3000 rpm (this is typical of stock cams) you will be very disappointed and may actually loose power overall cuz everything is mismatched.
in general, most import cars/motors are setup for power at 3000-4000 overall. the intakes are typically tuned for about 75%-80% of the redline rpm, while everything else is tuned for 3000-4000 for driveability and typical street use. most people drive their cars at 2000-4000, so the factory tunes most aspects of the motor for that range, but while allowing it to stil operate with moderate power at high rpm's which they accomplish with the intake. hence why porting and polishing our intake and head doesnt do much for power when n/a.
our port length is practically perfect for higher rpm power, and our port size is pretty close to perfect for higher rpm power for an n/a
my suggestion and opinion; just remove casting flaws, port match all mating surfaces in the intake tract, and polish all ports/runners. anything more than that is pretty much useless unless you go with a turbo running over ~8psi
As Dano said :emthup:
And now I've read it pretty much what motoxxx said as well.
If you are paying someone to do it I'd just save your money for something more worhwhile. Maybe a beer or twenty.
I had mine done while the head was off to simply match the ports better and clean it up generally.
Hardly any work was needed and tbh if I'd been paying for the time I wouldn't have bothered.
You will not notice any gains on the butt dyno.
On a real dyno you'll possibly see some gains but not a lot.
And don't forget that if they don't know exactly what they are doing it is easy to end with a head that is actually far worse than stock.
yep, thats the problem with hondas. well, actually the good thing about them too, depending how you look at it lol. the runners and ports are already built so well, that you will very rarely see/feel any gains at all when porting and polishing. at least 75% of the time you will either see/feel nothing, or will actually ususally lose power from it unless done perfectly, and tuned for a specific rpm along with tuning everything else for that exact same rpm like said above
port matching a polishing are about the only things you can really do for slightly more power, and its not even all that noticeable unless you have a lot of other mods done to match.
and yes, what dano said, porting and polishing domestic heads and runners usually gives really good gains, but mainly just cuz of the fact that they absolutely blow from the factory. ports are not even close to being the littlest bit matched, many more flaws in the castings, runners are never the correct length or size, basically domestic motors are just thought up, built, and thrown together with no actual decent technology in the tuning of them. which is the only reason porting and polishing a domestic intake/head gives such great gains, cuz they absolutely suck to begin with.