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Discussion Starter #1
good afternoon and happy holidays to all

i have an 08 zx10, interested in getting some head work dont, just a basic stage one type job, maybe some springs. Stock cams, bottom end, prolly a thin head gasket.

I know the tried and true premise behind a port and polish...smooth out and create more air flow in the cumbustion chamber...

the epoxy port jobs is what im naive about...i believe its trying to increase velocity and get as much air into the chamber.

Any education on the matter..pros cons insight would be greatly appreciated.

its about that time for the head to come off and ship out, and get right for '11:buttrock:
 

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Discussion Starter #3
thanks...good reading...thanks. Pm'd garth...looking forward to his response.
 

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Supercharged Mod
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This is a tricky business. It has to do with the cross-sectional area available for flow in the head. If the area is too small, it'll choke off flow at high revs. If the area is too large (which is a much more common scenario on production 4-valve heads) it reduces the "ramming" effect that happens when the piston stops at the bottom of the intake stroke but the flow in the intake runner is still moving.

Swiped from a post on another engine-building forum when I posed this same question ... Use millimeters for all of the diameters and areas, cubic centimeters for the displacements, the percentage as a number (i.e. 100% = "100") and metres/second for the velocities (yes, it's a little inconsistent but it works out)

CSA cross sectional area = (RPM x displacement per cylinder x volumetric efficiency) / (3000 x target velocity)

Use the RPM at which you want to make peak power, and 110 is a good target volumetric efficiency which will get it close enough.

"I use mm when I calculate. The velocities I use are:
120 m/sec. for the CSA.
105m/sec. for the intake flange.
62m/sec. at the intake bell mouth with IR manifolds.
84,5m/sec. at the plenum entry for plenum manifolds.

The manifold areas are for the runners and not with the radius on top.

So for 250cc at 12000 rpm (12000 X 250 X 110) / ( 3000 X 120) = 916,7 mm squared. two 24.15 mm holes.
With 30mm valves the velocity past the valve is 77.8 m/sec. and that is good. Intake length is depending
on the camshaft duration but somewhere around 10.6" for the 2:nd harmonic and 7.4" for the 3:rd but that
is too short so I believe the 2:nd harmonic will be best. If the average runner velocity is 100 m/sec. the
intake volume will be 296cc:s or 118% of cylinder volume. The shorter tract will only have 206 cc:s and that
is only 82% of cylinder volume. Another thing to look at is the runner angle, it should not become too steep.
If I remember right, more than 4 degrees total taper is steep. something like 2 degrees is more normal."

Reference (and the thread is a good read)

http://speedtalk.com/forum/viewtopic.php?f=15&t=23004&start=45

I took this and applied it to a different engine in a single-cylinder engine simulation program that I have. It gives very close to optimum results in the simulation program. I'm in the process of building an intake runner for a different engine to validate this "in the metal". According to this, the production 4-valve heads that I've seen all have cross-sectional areas which are too large. My FZR400 has carbs (throttle bodies) that are too large.

Note that my 250cc per cyl and 4 valves/cyl and 12,000 rpm target HP ain't too different from a ZX10R :lol:

If you plug in the numbers for the intake bell-mouth (62 m/s) you get 1774 mm2 which is about 48mm diameter ...
 

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whoa...slow the wagon. Too much math for a coonass!! :eyecrazy:

Why would the factory not shape the intakes like the epoxy heads if they are better? (serious question)
 

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Discussion Starter #6
This is a tricky business. It has to do with the cross-sectional area available for flow in the head. If the area is too small, it'll choke off flow at high revs. If the area is too large (which is a much more common scenario on production 4-valve heads) it reduces the "ramming" effect that happens when the piston stops at the bottom of the intake stroke but the flow in the intake runner is still moving.

Swiped from a post on another engine-building forum when I posed this same question ... Use millimeters for all of the diameters and areas, cubic centimeters for the displacements, the percentage as a number (i.e. 100% = "100") and metres/second for the velocities (yes, it's a little inconsistent but it works out)

CSA cross sectional area = (RPM x displacement per cylinder x volumetric efficiency) / (3000 x target velocity)


Use the RPM at which you want to make peak power, and 110 is a good target volumetric efficiency which will get it close enough.

"I use mm when I calculate. The velocities I use are:
120 m/sec. for the CSA.
105m/sec. for the intake flange.
62m/sec. at the intake bell mouth with IR manifolds.
84,5m/sec. at the plenum entry for plenum manifolds.

The manifold areas are for the runners and not with the radius on top.

So for 250cc at 12000 rpm (12000 X 250 X 110) / ( 3000 X 120) = 916,7 mm squared. two 24.15 mm holes.
With 30mm valves the velocity past the valve is 77.8 m/sec. and that is good. Intake length is depending
on the camshaft duration but somewhere around 10.6" for the 2:nd harmonic and 7.4" for the 3:rd but that
is too short so I believe the 2:nd harmonic will be best. If the average runner velocity is 100 m/sec. the
intake volume will be 296cc:s or 118% of cylinder volume. The shorter tract will only have 206 cc:s and that
is only 82% of cylinder volume. Another thing to look at is the runner angle, it should not become too steep.
If I remember right, more than 4 degrees total taper is steep. something like 2 degrees is more normal."

Reference (and the thread is a good read)

http://speedtalk.com/forum/viewtopic.php?f=15&t=23004&start=45

I took this and applied it to a different engine in a single-cylinder engine simulation program that I have. It gives very close to optimum results in the simulation program. I'm in the process of building an intake runner for a different engine to validate this "in the metal". According to this, the production 4-valve heads that I've seen all have cross-sectional areas which are too large. My FZR400 has carbs (throttle bodies) that are too large.

Note that my 250cc per cyl and 4 valves/cyl and 12,000 rpm target HP ain't too different from a ZX10R :lol:

If you plug in the numbers for the intake bell-mouth (62 m/s) you get 1774 mm2 which is about 48mm diameter ...
:eek::eek::shady:

(blinking, blinking.)
Uhh...hmmm....uuhhh...hmmm....soooo that means, i go fast??!?!?!?...lol

thanks, in laymens terms ultimately im asking is an epoxy job more advantageous than the traditional port and polish?? Peak hp, 1/4 mile is my vice...
 

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Slippery slope, hard to choose. If porting, you might be better off (time & $$$) just blending the valve seat transition (in the port runner) and removing the factory maching ring seen around the valve face pocket perimeter in the combution chamber. Garth is the epoxy head man. Contemporary street performance heads, in general, don't respond well to being hogged out. Don't leave out a proper valve job, ie 3 angle or 5 angle. And don't let your tuner sink the valves into the heads, the good ones already know.
 

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I have yet to see a expoxy head that performs well....You might gain low end power but you will lose top end....If this was so good everyone would be doing it....Go with a port n polish it works.....
 

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Supercharged Mod
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whoa...slow the wagon. Too much math for a coonass!! :eyecrazy:

Why would the factory not shape the intakes like the epoxy heads if they are better? (serious question)
That is a GOOD question. I don't know the answer but have only a couple of ideas why they might do that.

For the high performance applications (ours) it's possible that they're designing and flowing the heads to work at the RPM level that they will be using in World Superbike or other spec series (beyond stock redline). If you plug in a bigger "RPM" number you get a bigger cross-sectional area. The problem is that for the rest of us mere mortals, who are living with stock redline and stock cam timing etc., it results in a loss of mid-range.

It's also possible (I would say, likely) that they are designing it for peak power right at redline, so that the advertised number is as big as possible. The problem again, is a loss of mid-range.

In other cases (my test-bed engine) it's because the throttle body is common to several other engines, including some with larger displacement, and it's sub-optimal in this particular application.

The dreaded word "emissions" can come into play, too.

Having said that ... I just went downstairs and checked the diameter of one of the two inner velocity stacks from my ZX10R that I took off a while back, and it's bang on what the calculations above say it ought to be.
 

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I have yet to see a expoxy head that performs well....You might gain low end power but you will lose top end....If this was so good everyone would be doing it....Go with a port n polish it works.....
WELL i have a expoxy head done by Ryan K and im very happy im about 200pds and it still pulls hard asss helll on the big end, But i dont have just a port n polish to compare. and`i got strong val springs that i know is taken away some HP just my 2cent. just get some nos 30 shot:crackup:
ONE more thing dont just get a head and know cams you will really be mad
 

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Supercharged Mod
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I have yet to see a expoxy head that performs well....You might gain low end power but you will lose top end....If this was so good everyone would be doing it....Go with a port n polish it works.....
I know of a number of heads that have had the ports professionally re-shaped, which includes both "epoxying" and removing material from selected areas. Some of them are race winning bikes.

The key is to get the correct cross-sectional areas. What those cross-sectional areas need to be ... is up to the tuner to know.

Arbitrary changes in cross-sectional area - either too big or too small - will cost power.
 

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Newfie Bullet
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OK just so we are alllll clear about this..Im not 100% sure is my memory is correct...

I do seem to remember a discussion on this a ways back..Now i dont know if the link on page 1 will cover this or not buttt..It seems to me kawi got better flow with a somewhat unpolished head..Seems to me it responded to the rough surface for better air/fuel mixture in the combustion chamber..
 

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OK just so we are alllll clear about this..Im not 100% sure is my memory is correct...

I do seem to remember a discussion on this a ways back..Now i dont know if the link on page 1 will cover this or not buttt..It seems to me kawi got better flow with a somewhat unpolished head..Seems to me it responded to the rough surface for better air/fuel mixture in the combustion chamber..
Ask yourself why a head with rough surfaces would flow better - or make more power. I'll give you guys a hint and see where this goes.

A smooth surface - such as a polished port - has a thinner boundry layer than a rough surface port. If that's so, then a polished port will act larger (differential in boundry layer thickness) without actually being so.

Don't get caught up in fuel atomization diatribes. Our injectors these days are so far above what could have been dreamed of in the carburator days it's not funny. Throw the atomization BS out the window please.

Last question: why would you want the exhaust port smoother than the intake?

Remember that this is a SYSTEM. The intake, starting from the air box to the velocity stacks, throttle bores (and their pumping losses) to the ports, then to the valves and their special angles and chamber relief tricks (proper chamber unshrouding) - to the over filling effect proper cams and cam timing help (or hurt) with. The blow-down of the exhaust, the effect of pressure and sonic pulses on the exhaust flow relative to its cam timing and duration - then where is the primary tube length relation to the collector? All that and I left out about 20 more things.

Anyone that tells you that all the top manufactures are doing it wrong and they need epoxy ports (read smaller) is full of crap. Let's do some A-B testing (like I have done many times over the last 30 years) and we'll find out. If you are stuck with stock cams that are too big for the engine, for the application intended, then I can see where altering timing and smaller port size makes sense.

I will take a wide powerbanded bike making 150 hp over 4000 rpm range rather than a narrow band one peaking at 170 but only at 150 across 2000rpm any day.
 

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Newfie Bullet
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Settle down shoginator..I never said to do one thing or the other..All im sayin is that it was only a tear or two ago i remember reading something about porting and that kawi purposely left the ports roughed up..It maybe on a microscopic level but non the less they did it for better fuel air mixture..
I "THINK" what the point was to have the air/fuel monocules to mix better and rub creating a frictional increase of heat to aid in combustion..Same idea in a desiel engine(but they use compression to get ingition)
Like i said im just goin off memory of what i "THINK" i was reading a yr or two ago when this was discussed for the gen 3 when it came out..

IM NOT A MECHANIC nor am i a TECH SCHOOL GRAD of any sorts,i just do basic maintaince and go from there,this is just somethin of zx10r.net discussion i vaguely remember reading ..
 

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Craig dude chill buddy. That wasn't aimed at you. It was a series of questions one has to ask themselves as they go through the thought process. OK, I may have laid it out the way I would in a seminar (and I know this isn't one).

And Go Faster was right on when he said, "Arbitrary changes in cross-sectional area - either too big or too small - will cost power.


OK, I'll pop the cork on a good Zin and kick back now.
 

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Newfie Bullet
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Its all good shogunator..I wasnt freakin or anything..Just maken my point that it was a past thread on here and that my memory is foggy about what was said..
Im chilaxin with some beerskis myself..Its the holidayzzzz and the only time i get to suck back lotsa sudz without the worry of driven anytime soon..I drive a rig so i totally clear my head atleast a day before i roll again..
HHHMMMM..Shall i have a bud lime,corona or capt morgan spiced rum..hhhmmmmm so many decisions..lol
 

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Supercharged Mod
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Also keep in mind that a professionally built head could involve *very subtle* changes in port shape, to fine tune what the engine builder wants out of the engine - by people far smarter in these regards than most people here including myself. It's all about tailoring those cross-sectional areas to work best in the RPM range that the engine is being built for.

I haven't been privy to seeing the insides of those cylinder heads, but I'd wager that on newer engines that are already pretty good from the factory, any epoxy that they're using is just a fine smidge of it ...

and on the other matter, Bud Lime is good stuff :eek:ccasion1
 

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Discussion Starter #20
so the consesus is that their is no consensus.....some think highly of it while others dont...hmmm?? Just trying to get a solid answer if it is more benficial than a traditional port and polish, real world i mean....although i definately appreciate the theory.
 
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