The topic was head flow and potential, there is a lot to be gained by reading threads like this.
pink - stock KLZE head
blue - stock KL head
red - improved KL head on stock valves
red - stock KLZE head
green - improved KLZE head on stock valves.
Stock kl head = Improved KLZE head on stock valves.
From the man himself:This is another car and first 2 are with big valves(but haeds are different as ze and de)
It means, that if you plan to improve heads seriously you should make right choice, because the rusult will improve progressive.
This thread, and many others in the PT archives, are worth the read!!!Michael Perry aka KLZE Porsche wrote:I somewhat hate to post any of my info anymore because someone is either very quick to jump onto me or the serious doubters come on with no real good input and only a goal of being troublesome. But I will try this I guess.
I think if some people on here know how much experimentation I have done with heads they would back me. I have cut heads apart for porting templates, water flowed heads but not with a professional metered set-up, ported both KLZE heads and KLDE heads to the max possible limits, experimented with combustion chambers, experimented with valves, made metal exact-porting templates, and I am now experimenting even further with some radical port shaping.
In all of my experimentation I have gotten better results with the DE heads no matter which cams were used. I tried KLDE cams on both, KLZE cams on both and KLG4 cams on both. And yet - the results were always the same. I was always able to get better results out of modifying the KLDE heads.
The reason for this is that the KLZE ports are not the most efficient flowing design. And there is a lot of mis-information that KLZE valves are larger and I have never found any KL31 heads yet that had larger valves. I have swapped valves back and forth from KLZE to KLDE and visa-versa. Also there is a lot of mis-information about installing larger valves. If you install larger valves alone this will actually reduce your hp because you are increasing your obstruction of incoming air/fuel mixture. To properly install larger valves you would need to install larger valve seats. How can putting a larger obstruction in front of an identical sized orifice increase flow? It can't. The orifice is still the same size and you have only increased your obstruction. Also larger valves without de-shrouding the chamber increases your valve shrouding which also reduces your flow into the cylinder.
I found that the KLZE heads worked best with very minimal porting and with port matching. I found that KLDE head performance could be significantly improved and like I said - I got better results out of the KLDE when I worked them.
Remember that both castings are very similar externally. So this means that since the KLZE larger ports have less material around them to work with before you get into the danger zones with too thin of walls. I call this water injection. So you are limited on what you can do in the ZE port. But when you look at the DE heads - the port shape is better to begin with and the meat around the port is thicker and so you know what you are doing - they can made to flow significatly better because of a more efficient port shape. And when done correctly they WILL outflow KLZE heads because of the in-efficiency in the KLZE port shape.
It is true that larger ports will flow better under forced induction because with FI you want the least restriction possible and with not as much concern for flow efficiency. But when it comes to N/A and making the most possible - port shape and efficiency as well as combustion chamber anre extremely important.
If you are serious about making NA Power(All Motor in other words) with a K series engine, you will need to look into every little detail. It's not easy to make big numbers this way, so only go this route if you're in it for the long haul.