D PORTING KZ HEAD

I have read a lot of forums and thoughts on D porting a kz head. I have started to do some portwork on my head and I am needing tips and pointers on how to achieve my goals in this engine build, Its an 1197 with z10 cams 37in 33ex, I will be riding street and strip. On the d port its to keep the floor of the port which is the shortest route to the valve alone. I have read forums from you guys, namely Larry C, did some math with the stroke and bore and max rpm range 9500-10000 CSA should be 34mm. Now I haven't figured out what the measurement should be on the width of the bowl, considering the throat is where you should start or where some people start. Also if port velocity is so important, why not add epoxy to the floor to raise it up shrinking the port size towards the pocket gradualy to give it great velocity. I know around 300 is the best FPS to shoot for , but Im not sure if I should just use the material that's there creating the D port is best or not even do the d port. And with the CSA needing to be 31mm is that right off the back of the intake boot or start off at the size of the carb outlet then taper it to 34mm? I have tons of questions please help THX Alan

Something like this?
My wife put all my discs with good pictures someplace,but I basically borrowed the idea from the late 60s bigblock chevy heads and scaled it back to Kawasaki port scale! :woohoo:
When I talked to him about it a couple years back he basically told me I was nuts for using that idea

did you post that here by accident?? :huh:

Nope,look at the exhaust port.
It is a D layed on its back like youre talking about,If I can find some better pictures I will post them.

thx man , Larry actually has a picture of a head he is flowing on his website and its CLEARLY D ported

That's an intake port in his picture,Ive never seen it done on intake ports.
Ive only seen it done on the exhuat ports like I do mine anyway.

My question is how do you transition from the round carb boot to the intake port?

the intake side of the boot would be the same as the intake port, quickly blended to the round bore of the carb

Would it be better to start the D about midway through intake port to keep the velocity up kind of like a tunnel ram intake before the transition?
Im no expert,just a self taught guy .
I try and think of it in terms of how water would flow through pipe or how the Freon returns to compressor through the suction in an hvac system.If you dump same amount of Freon through to different systems one with a 3/4" suction line and the other with a 7/8" suction line the 3/4" suction line will work more efficiently

true I see what your saying, but it would act like a ramp for the air, I would think causing turbulence,and also anytime you remove the material off the floor your lengthening the runner, just like in a chevy motor , short runner dual plane intakes = more torque longer larger runners = more top end horsepower at the sacrifice of torque. The shorter the runner the lower in the rpm (say 1500-5000) band it builds power when on the longer runners power comes in later(say 3500-8500 but builds longer. I also am a self taught reader lol

prostreetkz wrote: true I see what your saying, but it would act like a ramp for the air, I would think causing turbulence,and also anytime you remove the material off the floor your lengthening the runner, just like in a chevy motor , short runner dual plane intakes = more torque longer larger runners = more top end horsepower at the sacrifice of torque. The shorter the runner the lower in the rpm (say 1500-5000) band it builds power when on the longer runners power comes in later(say 3500-8500 but builds longer. I also am a self taught reader lol

On the intake side you have to take into consideration that more than air is moving through the port. The flat intake floor buys you two things. Better fuel distribution is one of them.

A concave intake floor tends to draw the fuel into a stream down the middle of the runner.

Exhaust port floor is DEAD..plain and simple. There's no short size for the gas to cling to for any distance to truly direct it. To effectively D Port a KZ exhaust you need to weld the floor up first. Test it yourself with a shop vac if you don't have access to a flow bench.

You can carve a D shape into what's there and get some benefit from it but removing material from the floor is just making an already dead zone worse IMO

ALL of the porting on both sides of the head is relevant to many factors. It's not a one shoe fits all scenario for port size. But shape is critical on both sides.

Keep in mind that the pressure during blow down on the exhaust side is significant. You can get a port flowing good for a live engine by sizing the exhaust throat to a particular size and not hacking the ports out terribly much, but it won't be detectable on flow bench at 1PSI as anything impressive. But the live engine likes it

I'm truly honored to have you on my discussion, Larry. Now I'm going to get somewhere, lol, That's interesting on the exhaust side, I have read similar info on the exhaust side for porting , really just polishing the exhaust side, maybe a little match porting is sufficient. I want to pick your brain on D porting the intake side. I have read you say it's only needed if the port size is large. First off tapering a port runner, being larger on the carb end and smaller on the valve end will indeed increase velocity is that what the idea is to do? I have a 37.5 intake valve, shouldn't 40mm rs mikunis theoretically work well? Match porting the carb slowly tapering the port to the intended throat size of 89% then blending that to the bowl in turn to the valve seat? I would love to talk to you on the phone , I have also posted this same topic on your forum , again thx larry. I have rs40 mikunis but Have realized I may need 36 or maybe 38s.Cams have 485 at .040, 37.5in 33ex 76mm bore kz 900 crank. I am wanting peak power around 95-10000 but is that to high with heavy stainless valves and steel retainers? about 60% strip 40% street. I think that's all your needing for CSA values Thx Larry