Author Topic: Head porting without flow bench: waisting time & money? (Read 10898 times)

maksuttt · « **on:** November 02, 2006, 10:25:38 AM »

Hey, guys!
I am working on my 811 cc engine and thinking about head porting (not a radical one). I want to use mild cam. I matched intake flanges and ports, made them smooth and still want more:). Valve job on the waiting list, head is glass blasted and checked for straightness. So, can i make basic porting without flow bench? Now i have time and chance to make it: guides are removed and valve job not done yet (so i don't worry about ruin it). I checked forum and available articles for reference, and flow bench is only one thing which stops me... Actually, i don't want to enlarge cross section too much, just want to make smooth curves, remove some material in area of guides. Not sure about valve pocket... Can it be done? Or better to do something else instead? Thanks!

Peter · « **Reply #1 on:** November 02, 2006, 12:39:37 PM »

Go for it.

Sam Green Racing · « **Reply #2 on:** November 02, 2006, 05:56:51 PM »

Send it to Mike Reick or at least have a word with him.

Porting is knowing where to take the meat from.

Get it wrong and you can ruin your head.

Sam.

crazypj · « **Reply #3 on:** November 02, 2006, 06:08:37 PM »

You dont need a flow bench to port a head. A flow bench is a comparator, it only tells you if you have higher or lower flow at various valve lifts but has no meaning to how an engine really operates. (compared to a 'stock' head) A flow bench uses steady state flow through a port, the engine operates on a pulse flow. Its probably better to use a parts washer to see where the flow is seperating from port wall and just take off the steps and bumps without radically changing the shape. ( may need filling instead of cutting out material) I have used flow benches to check heads done by this method and its always worked well with minor increases in flow but major increases in power and torque. An extra 10cfm per port doesnt sound like much (+10%) Its much more important where the gas flows than how much, particularly judging by the fake numbers some people put out (210cfm when bench will only flow 190cfm max)
PJ

maksuttt · « **Reply #4 on:** November 03, 2006, 04:11:16 AM »

I used to use water nozzle to test ports on 2-strokes. Worked well. Didn't think about using liquid for head porting. Great tip! Thank you, crazypj!
Hey Sam, i want to do porting myself. Thanks for advice.

MRieck · « **Reply #5 on:** November 03, 2006, 09:03:55 AM »

The tools you have will pretty much dictate your porting. You need 4" shank carbides to get to the guide boss. Those burrs are 1/4" diameter. You need to open the bowl and flatten the floor especially in the throat area. Have the machine shop bore the throat to 90% of the valve diameter. This is easy to do with a Serdi.

maksuttt · « **Reply #6 on:** November 03, 2006, 10:29:13 AM »

Thank you for tips, Mike! I have different carbide bits 1/4" for pneumatic die grinder and 1/8" carbide (and lots of others) bits for dremel with extension. What about epoxy filler use? Any 'special' brand names (heard about JB-weld)?
So, i have chance to make it successfully

Will keep posting (hopfully with pics).

MRieck · « **Reply #7 on:** November 03, 2006, 01:50:39 PM »

You won't have to fill the port in.

maksuttt · « **Reply #8 on:** November 03, 2006, 04:54:55 PM »

Ouch... I thoght i will need to... This is Hondaman post:3. In the heads: all of the inline fours except the 400-4 had breathing issues. Grinding a "pocket" above the intake valve(s) and matching the ports to the carb tubes will improve them, especially at high RPM. Polishing the intake valve(s) helps, too. Don't back-cut the intake valves or you'll pop off a valve head - an expensive day, at best. (Backcutting exhaust valves will make them burn, and quickly - the CB650 malady). Trim (narrow) the intake valve guide bosses for a smaller profile, and polish it. Smooth, but don't polish, the intake tract. If you're good at heliarcing, raise a bead about .100" high along the bottom of the intake ports (CB750 only) in a half-moon shape, then smooth it off along the sides so it "restricts" (apparently) the bottom passageway about 1/3 of the way around. The floor of the port should ramp up to it, then be fairly abrupt in fall-off on the valve side. Do this at the point where the intake track bends down toward the valve (no, it's not easy). Although not obvious, this mod creates some "free turbocharging" at RPM above 6000, all the way to 16000 (lots of work), which deals more with fluid dynamics than I will put into this post.
And here is Mike Nixon quote from his site http://www.motorcycleproject.com/motorcycle/text/cows-porting.html (sorry for using, BTW): A port whose ceiling squeezes downward under a valve spring, for another example, is improved by widening the tract at that particular point. This makes this point in the port's flow area consistent with the rest of the port. Or, as is true in many older engines, the port may need a hump filled in and the radius leading into the valve throat increased. In fact, nearly all engine's ports respond to increasing their radii. That is, reshaping its bends so that both inner and outer parts of the curve have as large a radius as possible. And grinding isn't the only way to do this. In fact, in professional porting, filling with welding or epoxy is much more common than metal removal.
So, if I dont need filling, it's only easier for me

Thanks for help!

750fchop · « **Reply #9 on:** November 03, 2006, 05:09:53 PM »

Have you seen this?

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

750fchop

maksuttt · « **Reply #10 on:** November 03, 2006, 05:23:49 PM »

Yes, i have seen. Thanks

Plus i seen information on mototuneusa.com and etc. I collected some information, but tips from 'real' people are the best. And discussable, of cause

MRieck · « **Reply #11 on:** November 03, 2006, 07:24:23 PM »

I have done "D" ports. Filling the floor gives more area to the short side making it more equal to the long side. Generally flow/velocity increase. This is much more effective in 4 valve heads as they offer much greater volume to begin with. A CB port is choked to begin with. I haven't seen any real racing heads disregard volume just for velocity. Now there are different designs secondary to flow stopping and starting quickly such as in roadracing. Some extra velocity is good because charge backs up after shutting the throttle and reversion is a real problem. Keep one thing in mind.....I don't care what you do in regard to ports. When an engine is turning at 10,000, 12,000, 14,000RPM charge is going in both directions all the time. Some times are just worst than others. If you want a basic guide find that Branch article from a hundred years ago. I've seen several Branch heads from the 1025 days and they weren't filled.

PS I see someone posted that Branch article.

maksuttt · « **Reply #12 on:** November 03, 2006, 07:37:44 PM »

Ok, I'll keep it in mind

Thank you for an advices. On monday gonna start this work. Should be fun:)

MRieck · « **Reply #13 on:** November 03, 2006, 07:42:13 PM »

Go slow and check your work often. It's easy to get one great port....the hard thing is getting the other 3 to be just like it.

sparty · « **Reply #14 on:** November 03, 2006, 07:59:38 PM »

Quote from: MRieck on November 03, 2006, 07:42:13 PM

Go slow and check your work often. It's easy to get one great port....the hard thing is getting the other 3 to be just like it.

Mike,

I just sent you a PM.

Sparty

maksuttt · « **Reply #15 on:** November 04, 2006, 05:18:55 AM »

Quote from: MRieck on November 03, 2006, 07:42:13 PM

Go slow and check your work often. It's easy to get one great port....the hard thing is getting the other 3 to be just like it.

I'll try to slow down:) Thank you again!

MRieck · « **Reply #16 on:** November 04, 2006, 06:01:23 AM »

Here are some pics....hope they help.

MRieck · « **Reply #17 on:** November 04, 2006, 06:04:15 AM »

One more of the intake floor.

maksuttt · « **Reply #18 on:** November 04, 2006, 01:17:57 PM »

OK! That looks good! Helps, for sure! I'll try to make a template (have no idea how to name it) of symmetric ports. So, i wish to make all of them are same. Mike, thank you very much!

MRieck · « **Reply #19 on:** November 04, 2006, 02:39:46 PM »

Quote from: maksuttt on November 04, 2006, 01:17:57 PM

OK! That looks good! Helps, for sure! I'll try to make a template (have no idea how to name it) of symmetric ports. So, i wish to make all of them are same. Mike, thank you very much!

You're welcome.

maksuttt · « **Reply #20 on:** November 12, 2006, 06:14:49 PM »

Finished work with ports. Now time for new guides, valve job, etc. Posting some pics (in cylinder # order). Not that good as MRieck's, but should be OK, i think...

maksuttt · « **Reply #21 on:** November 12, 2006, 06:15:53 PM »

And here some more...

MRieck · « **Reply #22 on:** November 12, 2006, 07:01:52 PM »

I knock the guides out first if I'll be replaceing them...it makes it easier to work on the roof of the port. Looks good. You can do a little more smoothing on the roof after the guides are out.

maksuttt · « **Reply #23 on:** November 13, 2006, 03:57:06 AM »

Hey, Mike! I used dummy guide (grinded in drill chuck -0.005") to control cutting; to prevent damage of guides bores then glass blasted ports and to make a picture. I worked without them. Also, i needed to remove metal intake manifolds. With them i couldn't use the air-grinder. Made some mess (thread gone on #2) and fixed it... At least, I made ports almost the same in cross section (dummy guide helped). As you can see (no pictures

), i did not touch exhaust side. Just blasted them with glass one more time.
Thank you Mike! Without your tips it could be much more difficult.
"You can do a little more smoothing on the roof after the guides are out." I decided to leave them as is...

Jay B · « **Reply #24 on:** November 13, 2006, 10:34:16 AM »

Really interesting thread, esp. since I'm going to try this on my 350f soon. A couple questions- Would it work to leave more material on the downstream side of the valve guide, ground into more of a boat tail shape to smooth airflow past the guide, or are you just better off without it? Maksuttt, did you do anything with the combustion chamber around the intake valves, or leave it be?

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Author Topic: Head porting without flow bench: waisting time & money? (Read 10898 times)

Peter