Thoughts on Port and Polish Head.

Pnp head isn't worth it and here is why:

I've ported several honda heads, and ones that are not as good as the K20Z3's. It's really difficult to improve on honda's ports. The only reason to mess with the ports is if you going to radically raise the peak power rpm, and we cannot effectively do this for two reasons: 1) Poor tuning options and 2) oil pump and connecting rod limitations that make engine revolutions in excess of the factory rev-limit very dangerous.

The only honda head that I was able to improve at all was the D16Y8 head, and only because it had a 'ski-ramp' type projection on the side of the intake ports to improve swirl for the sake of emmsions control. Removing it slightly improved the high-rpm power. This is the exception though, and not the rule. Show me the ski-ramp in a K20Z3's head.

It doesn't really matter what the port looks like to the eye, but rather to an air molecule. Put these heads on a flow bench and you will find that honda's expertise is laudable, and the chances of a first-time DIYer improving the results essentially non-existant. The honda ports I've worked on looked better to the naked eye, but did not result in performance increases except fot the D16Y8 exception previously noted.

I understand that most here desperately want to believe that there is free horsepower awaiting them if only the grab a die grinder and use it. But the simple fact is you do not produce 197hp from 122ci by leaving such opportunities. Honda's port shapes, casting quality, valve profiles, choice of CR, installed cam lobe centers, and intake manifold design are extraordinarily hard to improve upon, and essentially impossible to improve upon without non-stock cam timing and the ability to rework the factory ECU, as hondata does with their reflashes. When you combine these factors with the bottom-end limitations (oil pump and connecting rod), you are just wasting a lot of time and inviting serious durability problems by mucking with the internals.

Want to make drastic gains with a grinder? Pick up an old small-block chevy and have fun. After ruining a few sets of heads you might even do so. But even GM has fixed the errors in their designs long ago, and it's very hard to improve their current offerings withing the factory RPM range. Honda never did produce shlock stuff, and the K20Z3 is a prime example of their leading expertise in the very same areas this thread is recommending second-guessing. It's your car, time, and money, so do as you wish. I'm just not going to stand around and let the assertions made here go unchallenged. I went through alot of honda engines and parts trying to improve what honda grants us all.

Posted by Ray

I agree with Ray. The Honda K-series heads are very well designed, with the Z3 being one of the best. I consulted a few shops in the past (ERL, Church Automotive, etc.) and they pretty much agreed that a port and polish doesn't improve the air flow enough to make it worth while, especially in the case of naturally aspirated. Everything Ray said was essentially what I was told. Even in K20 head and K24 bottom end applications, porting and polishing the head is seldom done. However, a valve job has been known to help in that particular setup.

In my opinion, as reid1980 asked, gasket matching the intake manifold and head may be worth while if the head is out. But you don't need to remove the head to install camshafts or valvetrain components and the gains you'll get from gasket matching the head and manifold will not be worth the money you'll pay to get it done.

Porting and polishing the head, gasket matching and valve jobs on the K-series engines are typically done in dedicated race cars that have built bottom ends and need every little bit of power they can extract. However, this extra labor is not practical in a K-engine that's predominately a street car with a stock bottom end. It will improve your performance but it won't be worth the money you'll spend on the labor and the issues that will most likely arise in the long run.