WRECKSHOP
Expert Class
Posts: 359
|
posted April 13, 2009 01:04 AM
Cylinder Head Port Finish ?? Doug Meyer, please
What should the cylinder head ports finish look and feel like ? Rough, polished or in between ? Doug Meyer, Jim, Entropy, KZscott and whomever else with knowledge of this please respond accordingly ??? Thanks...
  
|
dougmeyer
Needs a job
moderated
Posts: 2713
|
posted April 13, 2009 06:14 AM
Not polished, slightly rough. Jim can probably give you a grit # for your sandpaper roll.
____________
It's not that I think you're dumb, it's just that so much of what you know isn't true....
|
KZScott
Needs a life
high on speed
Posts: 7235
|
posted April 13, 2009 06:37 AM
Doug, I was under the impression that IN and EX required slightly different finishes? (IN slightly rough, but EX polished) is this incorrect?
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
|
VincentHill
Needs a life
Posts: 6520
|
posted April 13, 2009 01:57 PM
quote:
Doug, I was under the impression that IN and EX required slightly different finishes? (IN slightly rough, but EX polished) is this incorrect?
SInce all agree in the intake, the exhaust has 2 things going for it! If it is totally polished then the amount of heat absorbed into the head will be less which I thought was a good thing! Second, Since it is under pressure (as opposed to the intake) I thought Polished was Better also! Let us both hear it from Dr. Doug.
On 2 Strokes I really Polished the Piston Dome but left the head the Satina look because I wanted heat to radiate into the head and not get absorbed into the piston. I was also told that even though the piston is all carboned up that it still reflects the heat when Polished under the carbon?
____________
Made History @ Daytona and still one fast old man!!
|
Shane661
Needs a life
Posts: 11494
|
posted April 13, 2009 02:54 PM
As for a slightly rough intake...is that to promote "tumbling" of the mixture?
Sorry if that is a dumb question.
Shane
|
shiphteey
Needs a job
Posts: 2529
|
posted April 13, 2009 05:41 PM
quote:
As for a slightly rough intake...is that to promote "tumbling" of the mixture?
Sorry if that is a dumb question.
Shane
What about a golf ball....where you have air going the dimples of a golf ball .... air over air for less drag?
A.
____________
Gemini Motorcycles
Topping out everything from Ninja 250s to nitrous ZX-14s.
|
KZScott
Needs a life
high on speed
Posts: 7235
|
posted April 13, 2009 06:20 PM
quote:
What about a golf ball....where you have air going the dimples of a golf ball .... air over air for less drag?
A.
srry to go off topic, but is this giving you any custom paint ideas Ali? 
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
|
oldkawboy
Needs a job
Posts: 2125
|
posted April 13, 2009 06:32 PM
I've got the head off my bike but I couldn't get a golf ball in the ports.......guess I gotta grind some more! :-)
Shane,
I've read when a slightly rough finish will help with atomization or something like that.
Dan
|
whitehendrix
Zone Head
fails!
Posts: 757
|
posted April 13, 2009 07:57 PM
yes the roughness aids in atomization 
polished ex aids in flow rates and latent heat absorption.
at least thats what i know.. 
____________
Duct tape is the handyman's secret
weapon. The black is for formal
occasions. - ZRXDean
ill never own a busa unless
someone gives me one.... and then
ill sell it -KZScott
|
dougmeyer
Needs a job
moderated
Posts: 2713
|
posted April 13, 2009 09:03 PM
Here's the short version:
When a fluid (air) flows over a surface, whether it's a wing or the inside of a tube (or a port) there develops a boundary layer between the area of no motion and full motion. Think of it this way- if you were to flow a fluid with a higher viscosity than air (like oil) over a flat plate, the fluid that s in contact with the plate (on a molecular level) would essentially be stationary. As you move away from the surface, the fluid accelerates until it matches the "freeflow" velocity. This acceleration process creates drag and reduces the area of moving fluid. This layer can be termed "laminar" or "turbulent". The easiest way to describe this is that in true laminar flow there is no turbulence. The point when laminar flow finally breaks up into turbulent flow is described by a "Reynolds Number". Low Reynolds numbers are very low drag, high Reynolds numbers are higher drag. (English Physicist Oscar Reynolds in the 1900's).
How thick is a boundary layer? A few thousandths of an inch in a port, a foot thick on a 747 wing. The breaking of the laminar flow into turbulent flow creates drag, and you want to avoid this happening suddenly. If you try and turn the air too quickly you get "flow separation" when the laminar flow suddenly breaks away from the surface and goes turbulent. From an airflow standpoint a smooth, laminar flow port with gentle curves would seem to be ideal.
So, about now you are asking yourself, " If laminar flow is good why do we like a rough surface?"
The answer lies in the fact that what we are flowing in the inlet port of an engine is a "mixture" of air and fine droplets of fuel. And it is more important to keep that fuel suspended in the air than keeping the flow laminar at all costs, because the slowing of the port flow in the laminar boundary layer promotes the fuel coming out of suspension and adhering to the port walls. Simply, the turbulent flow is better for combustion, even if slightly less good for flow. A higher velocity in the port mitigates the downside of the higher Reynolds number drag, so we strive for a high velocity port, as straight as possible with a slightly rough wall.
There is no mixture in an exhaust port, it is shorter, the velocity is much greater, so we want a smooth port there.
Doug
____________
It's not that I think you're dumb, it's just that so much of what you know isn't true....
|
KZScott
Needs a life
high on speed
Posts: 7235
|
posted April 13, 2009 09:12 PM
thats the short version? awesome info
im going to go dream about cylinder heads now....
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
|
tcchin
Zone Head
Posts: 867
|
posted April 13, 2009 10:14 PM
Shorter version:
Surface roughness promotes turbulent flow in the port, which is more resistant to flow separation (detaching from the surface of the port) than laminar flow. This is important because flow separation creates drag, and reduces the effective cross-sectional area of the port. The energy of the turbulent flow also reduces fuel dropout from the intake charge.
Examples:
The aforementioned golf ball: The dimples induce a turbulent boundary layer which sticks to the surface better, wrapping the flow around the ball in flight, reducing the pressure drop on the trailing surface of the ball, allowing it to fly further through the air.
Aircraft wings: Leading edge flow separation is bad because you need consistent airflow over both surfaces of the wing in order to generate lift and for the control surfaces (e.g., ailerons, flaps, spoilers) to work. If turbulence is induced, the air flow will stick to the top of the wing, generating lift and allowing the trailing edge control surfaces to do their job.
|
Y2KZX12R
Needs a job
CompetitionCNC.com
Posts: 3762
|
posted April 14, 2009 04:53 AM
 Edited By: Y2KZX12R on 14 Apr 2009 13:02
Great explanations guys.
I'll just add a little about application.....
Cylinder head porting and engine building in general is like law and medicine, you practice it. doctors and lawyers practice law and medicine because its a dynamic situation and its always changing and new theories and "results" are seen on a daily basis. If you read the many books written on porting over the years you will see as each book was written there were new theories and ideas in each one. Some carry over to each generation of head porters and some don't. So even some of the latest current practices may change over time as the dynamics of a running engine are under stood.
So, in the "old days"(early 1950's) "porting and polishing" was all the rage. Everyone had there heads "ported and polished". These were mostly very inefficient head designs that they were dealing with. OHV engines were the new hot ticket but flat heads were still the norm. The ports were so poorly designed that anyone going in there with a grinder couldn't help but make the port flow more air. Big power gains were had for all.
The guys hot rodding engines on the street found out that ported and polished heads ran like crap on cold start up. A lot of it was also the cams of the day that also were poorly designed compared to the cam ramp designs you can get now. The reason the engine didn't like to run cold was because there was no boundary layer in the port. Actually there still was but it was very thin now from the polishing. The fuel dropped out of suspension and ran down the floor of the intake port and trickled in when the intake valve opened. This fuel never burned and eventually went right out of the exhaust. So everyone put a manual choke on so they could keep the fuel mix extra rich during warm up to compensate for the fuel dropout. Once the engine was hot the fuel evaporation rate in the port covered over the problem to some extent. Plugs didn't last very long in those days. On a hot rodded ohv buick Nail Head you may have had to change the plugs every Saturday am for fun on sat night. The smart guys changed the plugs on sat night when the engine was hot. Throttle response still suffered from polished ports thou. Pure racing engines it wasnt a concern and polishing was the norm.
At some point guys like Joe Mondello in the 60's found that leaving the floor of the port as cast required less fuel when the engine was warming up and even smaller jets could be run and throttle response was better. The rough surface kept more fuel in suspension requiring less overall fuel for a good effective A/F ratio. With better designed carbs (Holley) in the 60's the atomization got much better and less fuel was needed to keep the A/F ratio in the sweet spot. Ports thou were getting bigger and bigger for more airflow and HP but velocities were getting slower and slower so fuel dropout was a battle still. Velocity helps keep the fuel in suspension to a point. So on the street, some polishing on oval port BBC heads was good and but was bad for rectangle ports on the street.
Speed up to modern times..... polishing the intake ports will give 1 or 2% more flow, and on modern designed high velocity ports and fuel injection will make more power once again because fuel droplet size is reduced even further now aiding in keeping the fuel in suspension. And throttle response is great .
Typically "polishing" on the intake port is fine for modern FI engines. But a mirror finish isn't needed just cut the casting roughness down with sandpaper rolls. Once the casting roughness is gone your done. Typically on dog leg automotive V8 head ports the short turn is where the highest velocity is and as Tim said if you make that area as smooth as possible the boundary layer is super thin and it helps reduce separation. I would only do that on a Port Fuel Injected engine. not on a carbbed or throttle body FI engine.
For the most part "polishing" is very over rated.
The exhaust.... I've heard and read all sorts of theories on the exhaust side. Most will say that polishing is good to reduce the carbon layer thickness. Some say that carbon layer thickness is good, it aids in keeping the velocity up in the exhaust port.
The carbon layer does help reduce the heat transfer to the exhaust port walls and this is more important on aluminum heads than Iron.
On the dyno I just haven't seen it matter one bit power wise. The exhaust is under much higher pressure and velocity when the exhaust valve comes off the seat.
I'm of the belief that a slightly thicker carbon layer on aluminum heads is a good thing.
Now from a sales point of view.
I have found when people are "shopping heads" they want the highest high lift CFM number they can find and the ports "polished".
Neither of which are the most important aspect of a good performing cylinder head.
I've talked to many other big name head porters in the country and they get the same thing.
Most customers like shiny bling and big high lift CFM numbers.
The conversations always start off "what cfm do the heads flow" I ask "at what lift?" they say "at 650". Like clock work.
____________
Y2KZX12R
CompetitionCNC.com
|
2000redrocket
Pro
Posts: 1662
|
posted April 14, 2009 08:21 AM
y2k some day u will be doing my head when time for the 1270 kit i just scored.
|
Y2KZX12R
Needs a job
CompetitionCNC.com
Posts: 3762
|
posted April 14, 2009 03:30 PM
Nice, get that 1270 kit in, you'll love it !!!
Our stage1 porting would be perfect for that 1270.
If your going to spray it we have a Nitrous exhaust port.
____________
Y2KZX12R
CompetitionCNC.com
|
KZScott
Needs a life
high on speed
Posts: 7235
|
posted April 14, 2009 07:04 PM
Hey Jim, just curious, I know you recieved my head for the valve job(thanks for the phone call ), but im not sure if you took it out and gave it a look yet, but could you tell me how i did with my port match/clean up? i didnt take away much material. mostly matching up the ex port to the pipe. if there are any little things i could do to improve it i would love to hear it!
thx
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
|
whitehendrix
Zone Head
fails!
Posts: 757
|
posted April 14, 2009 08:23 PM
Tim, Doug and Jim.. i always learn a little bit after your posts.
(or alotta bit )
was i ballpark at least on the latent heat absorbtion?
did you know that every time you learn something, you get a squiggly little line on the surface of your brain?
so. ya.. you can imagine my gray matter looks like my grandma's ass after a thread like this.
____________
Duct tape is the handyman's secret
weapon. The black is for formal
occasions. - ZRXDean
ill never own a busa unless
someone gives me one.... and then
ill sell it -KZScott
|
Y2KZX12R
Needs a job
CompetitionCNC.com
Posts: 3762
|
posted April 16, 2009 02:31 AM
It looks good Scott nice job. The chambers are very nice too.
WH, I've never seen anything conclusive on exhaust port finish...??? You could be right..??
____________
Y2KZX12R
CompetitionCNC.com
|
KZScott
Needs a life
high on speed
Posts: 7235
|
posted April 16, 2009 05:39 PM
Jim, when you do the valve job, since the IN are slightly sunk into the head(from the process), do you make the EX "match" since they are new seats, or do they end up where stock would have been? Im basically wondering how PTV will be affected(if its even measurable)
also, not to stray too far off topic, does the surface finish of the piston affect things the same way as the ports?
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
|
whitehendrix
Zone Head
fails!
Posts: 757
|
posted April 16, 2009 11:56 PM
Scott, i'll be willing to bet that finish has a minimal influence on the atomization or turbulence.. the onlty thing i can think of is maybe how hot the thing gets? as well as it's ability to retain carbon. i've noticed in alot of my rebuilds that smooth pistons are FAR cleaner than rough cast ones.. common sense there tho..lol
hmm.. makes ya think tho!!
Jim, i wanna say i've head that on a few occasions, but like you, nothing set itn stone.. just regurgitating info i've heard over the years.. theoretically it makes sense, but we know how theory goes!!
____________
Duct tape is the handyman's secret
weapon. The black is for formal
occasions. - ZRXDean
ill never own a busa unless
someone gives me one.... and then
ill sell it -KZScott
|
|
|
HOME
NEW TOPIC