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

[camelman]

No material was milled off the head. Also, improving airflow increases volumetric efficiency, which directly increases cylinder pressure by allowing more air into the cylinder. So, increasing volumetric efficiency increases your "real" compression ratio.


My seat of the pants dyno test had scientific basis. Prior to porting the head, 5th gear at 60MPH was too tall with just me on the bike, and I had to downshift to 4th to hold speed up Highway 101 from the Golden Gate Bridge to the Rainbow tunnel. I drove that route a lot and downshifting was always required. After porting the head, I performed the same run multiple times with my girlfriend on the bike in 5th gear at 60MPH and was actually able to accelerate up the hill while staying in 5th. That is evidenced-based correlation unless you choose to just not believe me in which case this entire exchange was just a waste of time.

I don't understand why this is such a contentious issue.

[Retro Rocket]

No material was milled off the head. Also, improving airflow increases volumetric efficiency, which directly increases cylinder pressure by allowing more air into the cylinder. So, increasing volumetric efficiency increases your "real" compression ratio.


My seat of the pants dyno test had scientific basis. Prior to porting the head, 5th gear at 60MPH was too tall with just me on the bike, and I had to downshift to 4th to hold speed up Highway 101 from the Golden Gate Bridge to the Rainbow tunnel. I drove that route a lot and downshifting was always required. After porting the head, I performed the same run multiple times with my girlfriend on the bike in 5th gear at 60MPH and was actually able to accelerate up the hill while staying in 5th. That is evidenced-based correlation unless you choose to just not believe me in which case this entire exchange was just a waste of time.

I don't understand why this is such a contentious issue.

I agree Camelman, the car I referred to earlier in this thread started out with porting the head, It made a very noticeable difference in power, then came a complete rebuild with Chevy flat top pistons, cam , Edilbrock manifold and bigger Holley carb and it went like a scalded cat, initially it was asthmatic and didn't breathe well at all, the porting by itself made a very noticeable difference, it was like taking half a ton of weight off the car, there was even a noticeable change in exhaust note. I remember a thread here somewhere about 7 or 8 years ago where all that was done to a 750 was head work, it made a surprising difference. I will say, some engines will respond more to just porting than others, some engines are designed more efficiently than others, the 750 is a very restricted head and really wakes up with a good port job, probably more so than other engines, although in my experience, head work always makes a difference, a good cam , pistons and a pipe will help get the most from the port work...

[scottly]

So then, aside from volumetric efficiency, there's no substantiation for the "significant" performance claims.

Volumetric efficiency is exactly where the performance comes from, Cal.
For those still curious about porting:
http://draftcycleworks.blogspot.com/2010/09/porting-honda-head.html

[RAFster122s]

Cool article Scott.
From what I recall the 550 changes HondaMan recommended was reshaping the football and building the dome before the intake where it(the dome) kicks in at higher rpms.So, I think the 550 porting was similar and not extensive.

[Retro Rocket]

here's a bit from an article on porting alone with simple to understand principals....

Porting and polishing removes detonation-causing hot spots and casting flashes, and increases the air and fuel flow characteristics in all areas of the head, including the intake and exhaust ports, valve pockets, and combustion chambers and all radii. More air flow equals more fuel which equals more horsepower and torque. This clearly increases performance, including fuel economy. Porting and polishing the cylinder heads can unlock more horsepower from your engine than you probably thought possible.

Porting and polishing the heads provides the finely detailed attention required to bring your engine to a higher level of efficiency. More than any other single factor, the porting process is responsible for the high power output of an engine. Nothing can take the place of properly ported heads. Moving air and fuel through the heads is a major problem for engines running at speed and head porting helps to alleviate this. The net result is more torque, more horsepower, and more fuel economy, all at less RPM. And there is more good news. While cams, blowers, and turbos wear out, porting and polishing your cylinder head never wears out (think, all of the good and none of the bad!). Now that we have brought this up again, remember that big cams and turbos and blowers all have a lag time. Properly ported heads do not suffer that same malfunction! So let’s get porting and polishing so you can enjoy more torque and more horsepower

 

[camelman]

Scottly and Retro, those are two of the articles that guided me on my 350f porting job. Great to see them again!!!

[seanbarney41]

CalJ, no reason to get upset because you can afford to have your porting done by the best...it's just that some of us others can't or choose not to afford it, so we have to try and do some research, try, maybe fail, learn from mistakes, etc.




...that's how #$%* works, right?

[RAFster122s]

I agree with calj, it is easy to messup a head. Cleaning up the flashing and matching intake manifold to the port is a good idea.  But attempting to do what Mike R. does by an inexperienced newb like many are when it comes to grinding a port and reshaping it is going to end in disaster for most. For what it costs for the porting work it is inexpensive.  All the valve increased sizing and other work on the head for deshrouding the valve and the amount of head skim to increase compression, and other work is going to cost additional money of course.  So, I will be leaving the reshaping work to people who know what they are doing,  as I don't have a stack of heads lying about to learn on, nor the resources to rebuild the top end numerous times while I experiment to get it right.

[MRieck]

I wouldn't recommend milling a head -10mm.....that's .400. Just go to 1/2" and call it a day.

[scottly]

It's not a contentious issue, in fact, your post continues to support my point. As for you not killing the head, from your referenced post:

"1) deck 10 mil off the head to raise CR from 9.3 to 9.76

1 mil=.001", Cal.

[Retro Rocket]

I tend to reject claims that aren't supported by evidence, that's just my nature. Sorry if it puts anyone off. Must have spent too much time in Missouri....

Ahhhh, an atheist I see....

[Retro Rocket]

Mornin Cal...

[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.

[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.