Topic: how to port 500/550 four cylinder head?

[scottly]

(still hoping someone would post some pictures of stock 550 ports.  perhaps they are not as bad as the middle year cb750 ports and thus easier to "ruin")

i have pics here but they are not great. they don't show enough to really understand what's going on but may be better than nothing.











and after mike had a go at them:

Those bosses around the intake valve guides are huge, at least compared compared to a stock K7 750 port! Have you got before and after dyno tests? Cal demands real numbers.

[RAFster122s]

Mike R would have them when he did the work I would imagine,  whether or not the info was given to flatlander is a question for him?  ...Unless of course Mike documents his work for his records.

[camelman]

I'm agnostic...aka a cowardly atheist.

Also, just to reiterate, 1 mil is 1/1000th of an inch.  That's much different than 10mm.

[Trad]

I'm agnostic...aka a cowardly atheist.

Also, just to reiterate, 1 mil is 1/1000th of an inch.  That's much different than 10mm.

I think Cal, Mike as well as myself were thinking 1 millimeter which is 39.3700787 thou. Why not just say 10 thou?

[scottly]

I'm agnostic...aka a cowardly atheist.

Also, just to reiterate, 1 mil is 1/1000th of an inch.  That's much different than 10mm.

I think Cal, Mike as well as myself were thinking 1 millimeter which is 39.3700787 thou. Why not just say 10 thou?

10 mil, or .010" are easier than 10 thousandths of an inch. Cal jumped to the conclusion that mil meant millimeter, and you and Mike were influenced by Cal's erroneous assumption. The term mil is commonly used in some disciplines to denote .001", although I prefer the decimal notation personally. Obliviously, no one would mill .3937" off a head.      

[flatlander]

Those bosses around the intake valve guides are huge, at least compared compared to a stock K7 750 port! Have you got before and after dyno tests? Cal demands real numbers.

and facts and figures thou shalt get:
http://forums.sohc4.net/index.php/topic,134863.msg1718250.html#msg1718250

[flatlander]

Those bosses around the intake valve guides are huge, at least compared compared to a stock K7 750 port! Have you got before and after dyno tests? Cal demands real numbers.

and facts and figures thou shalt get:
http://forums.sohc4.net/index.php/topic,134863.msg1718250.html#msg1718250

... of course in the world of real numbers everything is relative:
those dyno runs are not for the head alone but the whole system with pistons, cam, etc.
the cam is quite mild so helps a bit but not too much, the pistons are 59mm with higher CR than stock (10:1) which accounts for part of the difference. had to tell, for me at least, what part the head alone would be responsible for.
at least i left carbs and exhaust alone so keeps at least some things constant.

[calj737]

Cal jumped to the conclusion that mil meant millimeter

I didn't jump to any conclusion, I mixed up what I read in 2 separate parts of the original thread. It was a mistake on my part, satisfied?

Regardless of whether I made a mistake in presenting a numerical number, it has yet to influence his claims. And I still believe the article I linked (as well as ample other information) would dispel his notion of substantial performance gains simply from porting.

[MRieck]

I'm agnostic...aka a cowardly atheist.

Also, just to reiterate, 1 mil is 1/1000th of an inch.  That's much different than 10mm.

I think Cal, Mike as well as myself were thinking 1 millimeter which is 39.3700787 thou. Why not just say 10 thou?

10 mil, or .010" are easier than 10 thousandths of an inch. Cal jumped to the conclusion that mil meant millimeter, and you and Mike were influenced by Cal's erroneous assumption. The term mil is commonly used in some disciplines to denote .001", although I prefer the decimal notation personally. Obliviously, no one would mill .3937" off a head.    

I am sure someone has tried it.

[MRieck]

I'm agnostic...aka a cowardly atheist.

Also, just to reiterate, 1 mil is 1/1000th of an inch.  That's much different than 10mm.

I think Cal, Mike as well as myself were thinking 1 millimeter which is 39.3700787 thou. Why not just say 10 thou?

That's what I have said for years and years and years .....and years.

[FunJimmy]

This is going back a quite a few years but member Jonesy put together a great follow along post on porting his 550. He certainly made it look a lot less intimidating than some of you guys. 

Check it out: http://forums.sohc4.net/index.php?topic=17374.0

[DaveBarbier]

I'm agnostic...aka a cowardly atheist.

Also, just to reiterate, 1 mil is 1/1000th of an inch.  That's much different than 10mm.

I think Cal, Mike as well as myself were thinking 1 millimeter which is 39.3700787 thou. Why not just say 10 thou?

10 mil, or .010" are easier than 10 thousandths of an inch. Cal jumped to the conclusion that mil meant millimeter, and you and Mike were influenced by Cal's erroneous assumption. The term mil is commonly used in some disciplines to denote .001", although I prefer the decimal notation personally. Obliviously, no one would mill .3937" off a head.    

We use mills in the graphic industry for measuring thicknesses of films and laminates and such. I've never seen it used in machining or really anything else not related to thin sheets of things...maybe I should pay attention more, haha.

[Scott S]

This is going back a quite a few years but member Jonesy put together a great follow along post on porting his 550. He certainly made it look a lot less intimidating than some of you guys. 

Check it out: http://forums.sohc4.net/index.php?topic=17374.0

 That's the write up that I followed a couple of years ago on my '78 550K and again on my current STF2 build. Mike took a look at our pics and gave it a thumbs up.
 The '78 ran great. Idled and ran like a stock bike up until ~5800 RPM and the it really woke up. A noticeable difference over my other stock 550. Especially paired with the CB650 cam.
 I think as long as you don't go crazy, you probably won't do any harm.

[FunJimmy]

That's the write up that I followed a couple of years ago on my '78 550K and again on my current STF2 build. Mike took a look at our pics and gave it a thumbs up.
 The '78 ran great. Idled and ran like a stock bike up until ~5800 RPM and the it really woke up. A noticeable difference over my other stock 550. Especially paired with the CB650 cam.
 I think as long as you don't go crazy, you probably won't do any harm.

Ya, it's a well documented write up.

I totally get the justification for going the professionally ported route but for some it's the satisfaction of learning and doing that's attractive.

[calj737]

A noticeable difference over my other stock 550. Especially paired with the CB650 cam.

Did you happen to ride it after porting, and before the 650 cam? I'm just curious as to your impression. No doubt some decent porting and the cam would wake these engines up (a point I made early on).

[scottly]

I found this article quite interesting as a reference read some time ago when I was considering engine mods on a BMW airhead project I have underway. It, along with recommendations and other research from machinists have formed my position. You may find it useful as well.

What article??

[scottly]

Cal jumped to the conclusion that mil meant millimeter

I didn't jump to any conclusion, I mixed up what I read in 2 separate parts of the original thread. It was a mistake on my part, satisfied?

[calj737]

I found this article (http://speedstore.ca/head_porting.html) quite interesting as a reference read some time ago when I was considering engine mods on a BMW airhead project I have underway. It, along with recommendations and other research from machinists have formed my position. You may find it useful as well.

What article??

Fixed now.

[Scott S]

A noticeable difference over my other stock 550. Especially paired with the CB650 cam.

Did you happen to ride it after porting, and before the 650 cam? I'm just curious as to your impression. No doubt some decent porting and the cam would wake these engines up (a point I made early on).

 No. The porting and cam were done at the same time.

[calj737]

Cal demands real numbers.

Well Scottly, real numbers don't lie, unless the operator of a dyno makes a mistake (case in point, Ron's Phaedrus results). Had you not noticed the discrepancy in his graph, many would have believed (incorrectly) that his motor made 87# of torque. You knew instantly that was a flaw in the math.

And to an earlier point made, porting doesnt increase air volume, it increase air flow rate. No amount of porting alone will increase in measurable volume changes (aside from decimal place volumetric calculations) into the combustion chamber. That is essentially controlled by the cam/inlet valve, as you certainly know. So, without a substantial change in volume, even the negligible compression change due to a 10mil of head milling, theres no way he would see sufficient performance gains (as claimed).

I struggle to understand your sniping over it all.

I'd challenge anyone to send a bone stock motor to the dyno, get a true baseline, then send your head to Mike R and have him perform his best porting magic using stock valves, and compare the difference. On a 50BHP motor, I would be absolutely astonished if you saw a 5BHP gain. Which will result in a 3HP at the wheel. You think 3HP at the wheel is enough difference to experience under throttle? I don't. You'd achieve similar or better results with a tuned exhaust and dyno tuned motor than from porting. No 2 ways around it.

[camelman]

Cal demands real numbers.

And to an earlier point made, porting doesnt increase air volume, it increase air flow rate. No amount of porting alone will increase in measurable volume changes (aside from decimal place volumetric calculations) into the combustion chamber. That is essentially controlled by the cam/inlet valve, as you certainly know. So, without a substantial change in volume, even the negligible compression change due to a 10mil of head milling, theres no way he would see sufficient performance gains (as claimed).

I struggle to understand your sniping over it all.

I'd challenge anyone to send a bone stock motor to the dyno, get a true baseline, then send your head to Mike R and have him perform his best porting magic using stock valves, and compare the difference. On a 50BHP motor, I would be absolutely astonished if you saw a 5BHP gain. Which will result in a 3HP at the wheel. You think 3HP at the wheel is enough difference to experience under throttle? I don't. You'd achieve similar or better results with a tuned exhaust and dyno tuned motor than from porting. No 2 ways around it.

Volumetric flow rate = (volume of air per unit of time)

If flow rate increases, then the volume of air per unit of time will increase. If the same camshaft is kept in the engine, then the period of time for the air/fuel mixture to enter the cylinders is kept the same, but now there is a higher flow rate filling the cylinder. The result is an increased fresh mixture volume inside the cylinder throughout the RPM and throttle range, which results in higher cylinder pressures and more power. All of that with only porting.

BTW, decimal place volumetric calculations are real changes. Just because the change occurs on the backside of a decimal point it doesn't mean it is an insignificant change. If a volumetric efficiency change increases by 0.05, then that can represent well more than 5% of engine power because these engines operate below a volumetric efficiency of 1.00. In fact, these engines operate more around a volumetric efficiency of 0.85 at full throttle.

I think 3HP at the wheel is noticeable.

[calj737]

Let's examine your claims, Camelman:

Riding alone, you had to downshift from 5-4 to go uphill on your bike. Then you remove the head, port it, mill it, change the head gasket, and suddenly can carry a passenger up the same hill without downshifting. Hmmm....

For sake of argument, let's say your passenger weighs 100# clothed with a helmet (probably generous on my part). That is essentially depriving your motorcylce of 15HP. 7-10# equal to about 1HP of power gain/loss.

By your own admission on the last reply, you believe you'd notice 3HP at the wheel, yet, you've lost a net of 12HP simply by adding a passenger, but still your bike outperforms itself previously with a solo rider? That would mean that you somehow accomplished more than 15HP (a 30% gain in BHP) or a 300% increase net at the rear wheel. I'm sorry, your premise is absurd.

Now, like others, if you performed other modifications in conjunction, perhaps properly tuned your bike, rebuilt the carbs so it was finally running at its optimum, I can believe the net result was a far better running bike. But, dyno-dyno your results would be proved to be false numerically.

Simply changing rate of flow does not increase flow volume. If the volume of the cylinder is equal, the time to fill is reduced, not the volume increased. And my point about decimal place performance is to say the gains would be mathematically measurable, but insignificant in real world results.

To derive a real benefit of porting, the cam/intake formula must change, no way around it.

[seanbarney41]

I have lost interest in this thread....maybe if the op comes back with some more educated questions, I will jump back in.  Otherwise, I got butt dyno calibrations to do, on junky old low tech motorcycles with "ruined" cylinder heads. 

[camelman]

Cal, so much of what you're saying is wrong that I don't care to correct it. I stand by my claims, but not your incorrect and conflated analysis.

[scottly]

Cal, go back and read the article you linked. Does it say other mods need to be made for porting to increase power? No, it does not. Speaking of numbers, that article stated that for every 1 CFM in increased flow, that cylinder would have an increase of .255 HP. Looking at the graph from the old Branch article shows an increase of about 9 CFM at a lift of .300", with the stock carb, which would add up to 9.18 HP.