Professional porting

Don't know why but the post, posted twice...

Post edited by: larrycavan, at: 2006/10/09 17:05

Ok, what do you need to do in the bowls? I have read alot about this subject, although I've never tried it...YET! I understand what you guys are saying but although I've read about porting and opening and reworking the bowls, I've never really understood what you mean or are actually doing in there. Can you explain this and maybe have a few pictures showing before and after to see what you are doing?

:blink: im a shadetree wrench myself,you went right over my head with all that stuff!:Pi took a picture of that csr today,as soon as i dig up some more batterys ill post it.

Post edited by: wireman, at: 2006/10/09 19:00

racer54 wrote:

Ok, what do you need to do in the bowls? I have read alot about this subject, although I've never tried it...YET! I understand what you guys are saying but although I've read about porting and opening and reworking the bowls, I've never really understood what you mean or are actually doing in there. Can you explain this and maybe have a few pictures showing before and after to see what you are doing?

Don't let the math intimidate you. It's not meant to. I posted that data to help everyone that is interested. The CSA values [cross sectional area] are what you focus on more than focusing on CFM values alone.

Velocity is the name of the game. Get it right for the intended application and you'll be very happy with your results. Get the velocity wrong and you'll suffer the consequences.

It's commonly accepted that when testing on a flowbench at 28" of test pressure, your target, localized port velocities are from 250 - 300 Feet Per Second. Better target value of 280 - 300.

This is one reason you can have a head that flows more air than another head but doesnt' make the power of the lower flowing head. The velociy profile of the higher CFM head is wrong for the application.

If you look at the first photo I posted, you'll see the bowl area, as well as the port runner, has been reworked quite a bit from the stock version. The bowl area is the pocket on either side of the guide, just past the short side turn. It's right under the back side of the valve.

The throat area of the port [the opening at the bottom of the valve seat] is generally sized to 85 - 90% of the size of the valve. The more race like [high RPM application] the application, the closer to 90% you'll go.

Valve Size x .88 = throat opening size.

Now, just because you go opening that hole up, doesn't mean it's going to flow huge volumes of air.

Air doesn't like to do one particular thing, TURN.

The KZ and J heads can be classified as side draft port designs. As such, they suffer from having to make that bend down to the valve.

The area on the floor of the port where the air makes that turn is referred to as the SSR [short side radius] and can be a key area for improving flow. That is one particular area where it's good to widen the port out.

It's also a particular area where the velocity can become too fast and that in turn is helped by give it more area.

If you put a head on a flowbench and reached into the port with a J bend pitot tube, you can measure the velocity in local areas of the port. You would see that the apex of the SSR can become quite a bit faster than other areas of the port. At 28" of test pressure and max valve lift, it may exceed 400FPS. If the roof of the port in the same section of the port is down to 250FPS, you'll run into problems.

What happens when you have unballanced velocity in a port?

Turbulence happens. Flow separation happens. Both lead to fuel distribution problems.

I would take a head that flows 10CFM less than another if the velocity profile was better balanced than the higher flowing head. It will generally make more power over a broader range of RPM.

Do you want to know more?

Definitely! I don't have or have access to a flowbench, so take that into consideration. Would like some schooling on this in general but also some things I can do at home to help the port out for better flow with bigger cams, bigger bore, carbs, etc. I think most guys here are in the same situation so whatever you can help us with would be fantastic. But I personally am interested in anything I can learn about this.

Absolutely...glad to help out anyone that wants to understand this topic. It's been my passion for a long, long time.

You have view now of both ends of the port so you can compare that to a stock port.

Without a flowbench it's difficult to balance things out but you can get pretty close if you pay attention to details.

At the very least, you should try to buy a 100cc burette to measure port volume. They're inexpensive and come in handy anyway.

You want to keep the port volumes balanced and the CSA matched up between ports. Without a bench and a pitot, you can't measure the airflow very easily but if you at least have a shop vac and a piece of string, you could check for turbulence issues to a certain extent.

If you give me some more details on your engine I'll generate the cross sectional areas for you to cut the ports to. With careful work you should easily get another 10CFM out of the ports. That's not the potential that the port can yield but it's a good target value for your first attempt and will require the least amount of cutting. I've flowed heads that came from some places whom I won't mention that didn't flow much more than that and cost a fair bit of money..

I need the following:

Intended Application of the Motor - [will it see street use or just pure drag racing]
Carb Size
Cam Lift
Duration at .050"
Valve Sizes
Bore / Stroke [well at least bore..we know it's 66 on the push-pull]
Which crank - J or KZ
Intended RPM of Peak HP

THANKS! Larry,
I knew someone had all this figured out for these old bikes. I am no engineer but I follow what's going on (mostly). I was an assistant to an engineer that designed and installed specialized textile dryer ovens so I've used pitot tubes and have a basic understanding of air flow. I've done a number of home port jobs too. That is why I have been asking so may questions on the forum, I know you can't just hog it out and get the results I'm looking for. Here is my combo for a hot street motor with couple times a year drag strip evening:
72 mm bore (1075cc)
10.25:1 cr
KZ 1000 head
I 36mm valve
E 30mm valve
K410 cams: .410 lift, 266 duration (card does not specify if at .050, timing figures were for .030)
BS34 carbs
peak rpm 8500
From your photo it looks to me the runner was straightened a lot during the enlargeing, I was wondering if the factory runner was designed for a particular swirl?
Post edited by: Exitpupil, at: 2006/10/09 22:41

Post edited by: Exitpupil, at: 2006/10/09 22:48

Your right. The stock ports are designed to bias the charge and induce a certain amount of swirl. I always use a wand with a piece of string as an initial indicator of what's going on with the flow pattern of the port. It's surprising sometimes how dramatically the air will move in a specific direction.

If you've worked with pitots then you have a good understanding of velocity gradients. That will play in your favor if you decide to build or buy a flowbench down the road.

One really beneficial thing about working on motorcycle heads is they allow you to flow the entire intake tract and still be able to get some good velocity measurments. I reach right on through the carb or throttle body with the pitot. A little change in aiming the charge near the port entrance can have a dramatic effect on the downstream section of the port. I've seen air speeds pick up as much as 100FPS in certain sections of the port when the intake boot is installed. That happens with ports that have multiple bends to negotiate.

I'll run the calcs for you and post them tomorrow. If you follow the CSA for the specified areas, you should get fairly close to your objective.

Wow Larry, you really know your stuff. Care to give some exmples of what to do and what not to do with the results from both? Im talking doing certain things to specific parts of the port. Basiclly the theory and results to back it up. Anything beyond the very basic stuff please. I would love to learn more about this:)

To hit your target you could use a little more lift to increase the curtain area. You'll still get pretty good results.

65.599 Cubic Inches @ 8500 RPM with 120.0 % Volumetric Efficiency PerCent
Required Intake Flow between 128.8 CFM and 135.2 CFM at 28 Inches
Required Exhaust Flow between 98.4 CFM and 107.3 CFM at 28 Inches

600 RPM/Sec Dyno Test Lowest Low Average Best
Peak HorsePower 134.9 140.5 143.3 146.0
Peak Torque Lbs-Ft 90.7 94.4 96.2 98.1

HorsePower per CID 2.057 2.142 2.184 2.226
Torque per Cubic Inch 1.382 1.439 1.467 1.496

BMEP in psi 208.4 217.0 221.3 225.5
Carb CFM at 1.5 in Hg. 194 215 226 237

Target EGT= 1287 degrees F at end of 4 second 600 RPM/Sec Dyno accel. test
Octane (R+M)/2 Method = 96.3 to 95.8 Octane required range
Air Standard Efficiency = 61.12717 % for 10.250:1 Compression Ratio

Peak HorsePower calculated from Cylinder Head Flow CFM only
600 RPM/Sec Dyno Test Lowest Average Best Potential
Head Flow Peak HP = 145.7 155.3 164.9

---

Engine Design Specifications

---

Engine Size CID = 65.599 Intake Valve Net Area = 1.517
CID per Cylinder = 16.400 Intake Valve Dia. Area = 1.577
Rod/Stroke Ratio = 1.788 Intake Valve Stem Area = 0.060
Bore/Stroke Ratio = 1.091 Exhaust Valve Net Area = 1.036
Int Valve/Bore Ratio = 0.500 Exhaust Valve Dia. Area = 1.095
Exh Valve/Bore Ratio = 0.417 Exhaust Valve Stem Area = 0.060
Exh/Int Valve Ratio = 0.833 Exh/Int Valve Area Ratio = 0.695

Intake Valve L/D Ratio= .289 Exhaust Valve L/D Ratio= .347
CFM/Sq.Inch = 81.7 to 85.7 CFM/Sq.Inch =89.8 to 98.0

Curtain Area -to- Valve Area Convergence Intake Valve Lift = .354
Curtain Area -to- Valve Area Convergence Exhaust Valve Lift = .295

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Piston Motion Data

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Average Piston Speed (FPM)= 3680.50 in Feet Per Minute
Maximum Piston Speed (FPM)= 6004.13 occurs at 75.400 Degrees ATDC
Piston Depth at 75.400 degree ATDC= 1.1449 inches Cylinder Volume= 118.4 CC
Maximum TDC Rod Tension GForce= 3411.03 G's
Maximum BDC Rod Compression GForce= 1920.39 G's

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Current Camshaft Specs @ .050

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IntOpen= 23.00 IntClose= 63.00 ExhOpen= 63.00 ExhClose= 23.00
Intake Duration @ .050 = 266.00 Exhaust Duration @ .050 = 266.00
Intake CenterLine = 110.00 Exhaust CenterLine = 110.00
Compression Duration= 117.00 Power Duration = 117.00
OverLap Duration = 46.00 Lobe Center Angle (LCA)= 110.00
Camshaft installed Straight Up = 0.00 degrees

-Recommended Camshaft Valve Lift- - Induction System Tuned Lengths -
Minimum Normal Maximum Best Length= 11.063 2nd= 8.708
Intake = 0.394 0.425 0.467 3rd Best= 7.065 4th Best= 5.944
Exhaust = 0.388 0.418 0.459 Plenum Runner Max Entry Area = 1.701
Max-effort Intake Lift = 0.489 Minimum Plenum Volume CC = 213.2
Max-effort Exhaust Lift = 0.481 Minimum Plenum Volume CID= 13.0

Minimum Intake Valve Lift to prevent Choke = .425 Lift @ 8500 RPM

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Operating RPM Ranges of various Components

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Current (Intake Valve Curtain Area -VS- Time) Choke RPM = 8210 RPM [with 36mm intake valve]

Intake Valve Area + Curtain Area operating RPM Range = 5947 to 7947 RPM

Intake Valve Diameter RPM Range = 8765 to 10765

Intake Flow CFM @28in RPM Range = 6802 to 8802
___________________________________________________________________________

Best estimate RPM operating range from all Components = 6668 to 8668

Note=>The BEST Engine Combo will have all Component's RPM Ranges coinciding
___________________________________________________________________________



--- Cross-Sectional Areas at various Intake Port Velocities (@ 28 in.) ---
169 FPS at Intake Valve Curtain Area= 1.825 sq.in. at .410 Lift
196 FPS at Intake Valve OD Area and at Convergence Lift = .354
242 FPS 90% PerCent Rule Seat-Throat Velocity CSA= 1.277 sq.in. at 8500 RPM
350 FPS Velocity CSA= 0.882 sq.in. at 8500 RPM Port Sonic-Choke with HP Loss
330 FPS Velocity CSA= 0.937 sq.in. at 8500 RPM Smallest Useable Port CSA
311 FPS Velocity CSA= 0.994 sq.in. at 8500 RPM Recommended Smallest Port CSA
300 FPS Velocity CSA= 1.030 sq.in. at 8500 RPM Recommended Port CSA
285 FPS Velocity CSA= 1.085 sq.in. at 8500 RPM Recommended Short-Turn CSA
250 FPS Velocity CSA= 1.236 sq.in. at 8500 RPM Recommended Largest Port CSA
225 FPS Velocity CSA= 1.374 sq.in. at 8500 RPM Largest Intake Port Entry CSA
200 FPS Velocity CSA= 1.546 sq.in. at 8500 RPM Torque Loss + Reversion


--- Cross-Sectional Areas at various Exhaust Port Velocities (@ 28 in.) ---
162 FPS at Exhaust Valve Curtain Area= 1.521 sq.in. at .410 Lift
225 FPS at Exhaust Valve OD Area and at Convergence Lift = .295
278 FPS 90% PerCent Rule Seat-Throat Velocity CSA= 0.887 sq.in. at 8500 RPM
435 FPS Velocity CSA= 0.568 sq.in. at 8500 RPM Sonic Choke at Throat Area
350 FPS Velocity CSA= 0.705 sq.in. at 8500 RPM Port Sonic-Choke with HP Loss
330 FPS Velocity CSA= 0.748 sq.in. at 8500 RPM Smallest Useable Port CSA
311 FPS Velocity CSA= 0.794 sq.in. at 8500 RPM Recommended Smallest Port CSA
300 FPS Velocity CSA= 0.823 sq.in. at 8500 RPM Recommended Port CSA
285 FPS Velocity CSA= 0.866 sq.in. at 8500 RPM Recommended Short-Turn CSA
250 FPS Velocity CSA= 0.988 sq.in. at 8500 RPM Recommended Largest Port CSA
225 FPS Velocity CSA= 1.097 sq.in. at 8500 RPM Largest Exhaust Port Exit CSA
200 FPS Velocity CSA= 1.235 sq.in. at 8500 RPM Torque Loss + Reversion





Intake Intake Curtain Area 300 FPS Velocity Minimum Head
Valve Choke Square Inches Cross-Sect Area Flow @ 28 In
Lift RPM Intake Exhaust Intake Exhaust Int Exh
.050 1001 0.223 0.186 0.121 0.097 15.2 12.1
.075 1502 0.334 0.278 0.182 0.145 22.8 18.2
.100 2002 0.445 0.371 0.243 0.194 30.3 24.2
.125 2503 0.556 0.464 0.303 0.242 37.9 30.3
.150 3004 0.668 0.557 0.364 0.291 45.5 36.4
.175 3504 0.779 0.649 0.425 0.339 53.1 42.4
.200 4005 0.890 0.742 0.485 0.388 60.7 48.5
.225 4505 1.002 0.835 0.546 0.436 68.3 54.5
.250 5006 1.113 0.928 0.607 0.485 75.9 60.6
.275 5506 1.224 1.020 0.668 0.533 83.4 66.6
.300 6007 1.335 1.113 0.728 0.582 91.0 72.7
.325 6508 1.447 1.206 0.789 0.630 98.6 78.8
.350 7008 1.558 1.299 0.850 0.679 106.2 84.8
.375 7509 1.669 1.391 0.910 0.727 113.8 90.9
.400 8009 1.781 1.484 0.971 0.776 121.4 96.9
.425 8510 1.892 1.577 1.032 0.824 129.0 103.0
.450 9011 2.003 1.670 1.092 0.872 136.5 109.1
.475 9511 2.115 1.762 1.153 0.921 144.1 115.1
.500 10012 2.226 1.855 1.214 0.969 151.7 121.2


Ok...the center section of numbers are your CSA values that you need at that RPM. The CFM values are on the far right.

Predicted choke RPM is lower than your intended peak HP RPM 8210 vs 8500. The motor want's more curtain area. You get that from larger valve and/or more valve lift.

Should you decide to go with a .425" lift cam, you'll be within the streetable paramaters for suggested street cams for the motor.

On the other hand 37.5mm valves with the .410 cam allow you to hit your target very nicely.

---

Operating RPM Ranges of various Components

---

Current (Intake Valve Curtain Area -VS- Time) Choke RPM = 8551 RPM [with 37.5mm Intake Valve]

Intake Valve Area + Curtain Area operating RPM Range = 6195 to 8195 RPM

Intake Valve Diameter RPM Range = 9680 to 11680

Intake Flow CFM @28in RPM Range = 6802 to 8802

Flow converted from 28" to 10" = 80.7CFM [not difficult to achieve with bowl work and 88 - 90% throat size - [valve size x desired %]

Remember the CSA values are in Square Inches. You'll need some inside calipers and vernier calipers to measure inside the port.

You can also use a piece of formable wire that you can shape inside the port [end to end] and then measure it's length and use circular measurements to calculate the CSA. Effectively you are treating the length of the wire as the circumferance of a circle and calculating area from that.

Notice the suggested CSA = 1.030 Sq/In. That just so happens to calculate out to a circular diameter of 29.09mm [ever wonder why 29mm smoothbores work so well on these motors]

You can match the port entrance to your carb size of 34mm [notice the suggested largest port entry measurement...calculates out to 33.6mm]

I would suggest that in this particular head, you match the port entrance to the carb exit size and don't get fancy with flat port floors and "D" shaping just yet. Instead, form the port shape from the entrance of 34mm, down to the 285FPS dimension [29.8mm diameter circle]at the short side radius. You'll see you don't need to cut much to achieve that.

Form the bowl section of the port as follows. Looking into the port through the throat [valve seat area] you want to form the port and shape it so that if you reach down into the port with inside calipers and measured the width of the bowl, it is at minimum, 34mm if measured straight across where the guide divides the bowl. It's hard to describe that. You're widening the port on each side of the guide and transitioning the port roof gradually into the bowl.

Avoid getting low spots in the runner. They will hurt flow.

Avoid forming ridges. Carefully blend the seat and bowl together.

I like to open the throat before I do anything else. I open it up to nearly what the finished dimension would be and save that last little bit for final blending and shaping.

DO NOT POLISH THE PORT TO A MIRROR FINISH!

Get some polishing rools of #60 or #80 grit for the final finish.

Remember, you WILL need a good valve job when you're finished. If you need guides, now is the time to do them as well. A narrow 30* back cut on the intake valves will help the flow.

Be careful with the SSR. There isn't much short side material there to begin with.

Get a good single cut cutter for aluminum and start out by keeping the cutter speed very slow. You get lots of chances to take out minimal amounts of material but if you have that cutter spinning very fast and gouge a deep recess into the port somewhere, you'll play hell trying to straighten that back out.

GO SLOW - TAKE YOUR TIME.

Lube the cutter with ATF or WD40..not gallons..just a couple of drops. You'll eventually find a speed where you're comfortable with the cutter.

REMEMBER...The right speed of the cutting burr is the speed that allows you to have complete control of the cutter.

PS. DO NOT GRIND THE GUIDES WAY DOWN FLUSH WITH THE ROOF OF THE PORT! That's a big mistake with short duration cams. They need to control the valve.

Good Luck....

Why does this forum keep double posting on me? I have to go back and delete the duplicate post??? Never had that happen before...

Post edited by: larrycavan, at: 2006/10/10 00:10

77KZ650 wrote:

Wow Larry, you really know your stuff. Care to give some exmples of what to do and what not to do with the results from both? Im talking doing certain things to specific parts of the port. Basiclly the theory and results to back it up. Anything beyond the very basic stuff please. I would love to learn more about this:)

I'll post some more for you tomorrow evening. Getting late here in Pa and 5:30am rolls around pretty fast!

We'll discuss piston demand and how it relates to porting and pumping losses tomorrow evening...Glad you guys are interested!