Kz 1000 Head porting

So I have been working on the cylinder head off my KZ 1000 motor. I got everything glass bead blasted. Then went to town with my grinders. I have got the intakes pretty close to finished.... still need to match the manifolds.. but still waiting on 2 of them (only came in a set of 2.. not 4 like I thought:brick: ) I don't have a flowbench but have done alot of heads.. some good.. some not so good. I have also been doing quite a bit of research online as to what works and what doesn't.. So far it has turned out well...lots of meat was taken out but mostly just straightening of the ports. I am trying to keep the port velocity in a usable range. Seats will get 3 angle vavle job once i get done. I also have a set of Andrews springs and aluminum retainers to go in later.... Still on the hunt for the right cams. next is the exhaust ports..............:beer:

You're doing a nice job Here's a tip to help you out.

How big you you make the port is relative to how big the motor is and how fast you're going to spin it.

Here's an online calculator to help you out.

www.rbracing-rsr.com/calculations.htm

In the attached picture, I put a yellow line at the throat of the port. If this is a small bore street motor, measure that diameter and make it 90% of the size of the valve.

36 * .90 = 32.5mm

The runners are looking pretty good. Keep them nice and level. Avoid getting low spots in them.

Stock flow on those heads is generally 68CFM@10"water @.500" lift.


How big is the motor?

Here's a street cut port to look at. These typically make over 100HP at the rear wheel with 29 smoothbores, drop in cams and 1075 street compression pistons. Good torque throug the middle as well.

When you do the valve job, push the seat all the way out to the edge of the valve and then use the outside cutter one more time to narrow the 45 up so there's a thin, shiny line just outside the 45.

If you're cutting the seats by hand with Neway cutters, watch you don't get going crooked with the cutter. The T handle will quickly rock and the cutter will follow a crooked seat in a heart beat.

Best to just go in there first with a 60 and put a light cut in there to see how crooked things are.

Then, take the 30, go easy, keep the cutter straight and wipe the 45 right out. Go back with the 60, set your inside angle to the width you want, then cut the 45 lightly.

Put magic marker on the seat and set the valve in there. DO NOT SPIN IT. Pull it out and see where the seat locates and more importantly, how evenly the marker is dispersed onto the valve. It's a quick/easy way to check your concentricity.

Then adjust the location with the 45 and set outside location with the 30 and width with the 60.

If the head has never been touched, you're going to find the exhaust valves are seated way low on the face. They can be sunk a bunch to push the seat further out on the valve face.

The handiest thing you'll want is a 37.5mm round block to drop down in the bucket bore to check your stem height. You can make one or APE has them for an inexpensive price. I use mine all the time.

I love the work, done a lot of heads and 2 stroke cylinders. One place I worked in the 80's had a head flow bench. Some very wise people have been doing a rougher port contour on the inside closest angle of flow. And mirror polishing the outside angle of flow. Fuel droplets follow the inside track, and the lighter air flows around the outside of the curve, some roughness helps keep the fuel atomized. Also you may consider either narrowing the outside diameter or the valve guides or shortening them. Some of the KZ head guru's would know about longevity issues with shorting them. Also I didn't see if you retained the stock valves or were going stainless. Stainless will out flow the stock valves, you can also relieve around the valves in the head in the chamber, with a CC equalization, and polish. Then if you have the tools some more gain can be had from doing a 5 angle seat cut, but its really most noticeable when flow benching, once you do the port work and reassemble it will pull like crazy, so all little details will be in or out of the finished head.
Camshaft grind and carb work with a raise in compression, 4 into 1, ignition curve, etc will make it all work. Just hold on tight!

Thanks for the tips guys. You can never get too much advice. I just need to sit down one day and really spend the time on this head... I've been trying to do a little here and a little there... Always in pairs as to keep everything equal between sides. .. I've heard the 90% rule before .. seems logical to me. I havn't got too carried away with makin anything huge. I've tried that before with only bad results.. and junk heads! I usually try to just straignten out the port on the short radius of the bends. someone said 80-85% for mild engines and 90% for all out performance. try to unshield the underside of the valve a bit too. I kinda loose a bit of the pinch point but everything is pretty gradual and no low spots yet

As far as port texture... it will probably stay roughed up a little... on the intake anyway... exhaust may be smoother.

What grinds are you suggesting?

What carbs are you suggesting?

What is the motor to be used for?

In performance, you must give up something, to get something. What are willing to give up?

What is your intake port volume? What is the combustion chamber volume?

Street Applications - Taper but don't shorten the guide. It has an important job to do.

The flow is in the bowl on those heads

larrycavan wrote:

Street Applications - Taper but don't shorten the guide. It has an important job to do.

The flow is in the bowl on those heads

absolutely! easiest way i know to illustrate this is with plumbing fittings this first picture is a vent fitting,2nd is called a long sweep.same size pipe/port feeding each.which one do you thing drains/flows better?

heres a long sweep

eureka!!!
a bulb just went off

My bulb is still a bit dim. (Jokes expected here.)

1. If I understand Plummen's pvc example, then one of the goals is to remove some material at each end of the long radius (top of the port) and to remove some material from the center of the short radius (bottom of the port). Is this correct?

2. If I assume a set of 29s are going on and I use the 90% formula larrycavan posted above, then is it correct to assume that another goal is to have a gradual taper from 29mm to 32.5mm?