Topic: porting questions

[the technological J]

ive been reading lots of stuff on here and i here many people talk about porting and first level porting can anyone explain to me what porting is  and have any pics? hondamans famous thoughts talk about pocket ports... im confusted as what this is and how exact does porting have to be? is this done by touch or is this an exact science?

[Don R]

Porting is opening up the intake and exhaust ports by grinding and sanding.  As much art as science. Many automotive race heads are done by cnc machines these days, it is more precise and a good port can be duplicated over and over where hand porting is hard to duplicate. Pocket porting is just porting a specific area, I believe in the valve bowl. Too bad there is not a cnc program for us 750 guys. Yet.

[Hinomaru]

More info about CB750 head porting:

http://cb750k2.tripod.com/Technical/porting/Porting_the_Honda_Head.htm

[faux fiddy]

Kind of not a a 750 and in fact it's not even got a cam, but there may be something you can learn about similar tools and techinques on a two stroke  here (lots of pics):

[wannabridin]

Kind of not a a 750 and in fact it's not even got a cam, but there may be something you can learn about similar tools and techinques on a two stroke  here (lots of pics):

forget the link poor boi??

[faux fiddy]

Asleep at the wheel and BCS football..

http://www.teamsmoke.com/photo5_1.html

Several page #'s across the top link up to porting pics..

[RRRToolSolutions]

That old Branch flow-bench test Hinomaru posted above is some great information. Times have changed and while the article is clearly 35 years old or more - the test themselves illustrate the benefits perfectly.

Porting is not something you just do. Flow improvement is the key and just bigger doesn't mean more flow. You can actually slow/ruin a head if the shaping and sizing is not kept in concert. Mine was done with a Flowbench, but many good porters (Mike here) have done these so much - they know.

Here is an 836cc kitted bike that I've purposely twisted to 11,000 rpm (well past peak) just to make some noise for my camera. You can count the seconds involved - I pinned her throttle to the 120 mark. It's faster than my 1976 KZ900 fresh motored bike.

Porting is money well spent and does not cost reliability 1 bit -

Gordon

http://www.vholdr.com/node/49293

[Flying J]

I am doing a port job and I'm not using a flow bench. As stated above removing to much material or doing it un evenly can ruin your head. But what you can do your self is smooth and match the ports. That means removing the rough spots and casting marks and matching the intake and head surface to reduce unwanted friction. I am no expert but i believe this can be done with positive results without using a flow bench. I have ported/matched my head and it is awaiting a valve job. Then i will see how things turned out. If you look at the before and after pics in my thread you can see the casting removed.
http://forums.sohc4.net/index.php?topic=56904.msg614354#msg614354

[dave500]

the two stroke porting is a different kettle of fish in that it changes the event timing of fuel inlet and exhaust,a bit like a modified cam in a four stroke.

[sparty]

That old Branch flow-bench test Hinomaru posted above is some great information. Times have changed and while the article is clearly 35 years old or more - the test themselves illustrate the benefits perfectly.

Porting is not something you just do. Flow improvement is the key and just bigger doesn't mean more flow. You can actually slow/ruin a head if the shaping and sizing is not kept in concert. Mine was done with a Flowbench, but many good porters (Mike here) have done these so much - they know.

Here is an 836cc kitted bike that I've purposely twisted to 11,000 rpm (well past peak) just to make some noise for my camera. You can count the seconds involved - I pinned her throttle to the 120 mark. It's faster than my 1976 KZ900 fresh motored bike.

Porting is money well spent and does not cost reliability 1 bit -

Gordon

http://www.vholdr.com/node/49293

Gordon,

I love that video.  Just a bit under 12 seconds from a rolling start to 120 mph. 

Art

[larrycavan]

Hi Guys,

My first post on this forum. I've been browsing the porting threads for a little while. Some good info and some not so good info in them.

Here's a video of  testing a cylinderhead for velocity. In the video you'll see the actual speed through the port in feet per second at 28" of test pressure. In addition to the CFM [cubic feet per minute] numbers, the velocity is even more important.

It can be measured and the information put to good use. The amount of flow the head is capable of is one thing but if the cross sectionl area of the port is incorrect for the size of the motor and the intended peak horsepower RPM, then the combination won't always work properly.

In the video, you'll see  a port being probed with a J Bend pitot. In the computer screen shots, the number in the upper right is the air speed.

Sorry, it's not a Honda head but it's all the same relevance.


http://www.flowbenchtech.com/porting/CRH/velocitytest.htm