head porting

[mach1stang]

hey guys i have a peice of crap kazuma that i want to use for a test terd i want to try porting the head and see what it does if it go it gos if it blows i did it a favor but i was wondering if anybody here has tried porting stuff them selves and if so did make a diffrence

Porting is easy I just did it. I used a dremmel with a small grinding stone. I ported the carb too and found a small lip inside the header and ground that down too. Huge gain but im still trying to get it jetted right. Im adding boost ports tonight. But thats all on my 2 stroke motor.

[400exrider707]

Any redneck with a dremel can port, but getting it ported correctly is an art that only a few can perform...

Originally posted by 400exrider707
Any redneck with a dremel can port, but getting it ported correctly is an art that only a few can perform...

Not really its prity easy. Just have to know what you want to gain.

[bradley300]

lol, you need to know alot more than that!

[mach1stang]

yeah my dad has been helping me and he says if you get much air in it wont fire and if you get much air out you could screw a valve up but i dont know thats why i am trying it on a clunker

Originally posted by mach1stang
yeah my dad has been helping me and he says if you get much air in it wont fire and if you get much air out you could screw a valve up but i dont know thats why i am trying it on a clunker

You wont be getting really any more air in the motor as long as you you have the throttle closed while trying to start it. Once the throttle is opened is when you start getting more air.
Well You can go big as you want as long as the bottom of the piston don't come past the port. Bigger gives top end and you may loose bottom end.
You may be able to port the carb to. Might want to remove the air box too.
No matter what you will need to rejet.
port a little at a time to see how you like it.

Another thing to consider is how much your head flows. Keeping a small port with high velocity is a key to getting performance out of a head. Most people think grinding a big port will flow more air, when in reality it makes for sluggish performance and a nightmare to correctly get your carb jetted. It also will determine what size carb your engine needs. Each engine builder will have his own opinion on the amount of CFM a carb should flow over what your head should flow. A good rule of thumb for performance would be to have a carb that flows10-30 percent more than your port does at its highest lift. This is changing, however with the new style motors with their short rod-to-stroke ratios, lighter components inside the motor and multi-valve heads.

[mach1stang]

yeah i mean the ports are a little biger than stock, but mostly made to flow better.

[400exrider707]

Originally posted by bradley300
lol, you need to know alot more than that!

Ill post it again .... there is more than just removing material, you can do so much more with porting and just listening to nacs420 talk about it is example enough of why you should send it to a reputable builder... somone with vast knowledge on the subject. Lets see if one of the engine gurus can enlighten us on the subject....

[bradley300]

ive seen far fewer cylinder ruined by reputable builders than shadetree mecahnics. if you dont have any experience you really dont need to touch your ports yourself. if you are that hard headed and think you are that good, there are some porting programs for your PC that can be of a whole lot of help. basicly will let you port your motr and give you a thoeretical dyno before you ever go to the garage. yu can even change and change dimensions and gives you a thoereticl dyno to show what those changes would do. they are really neat, but i still wouldnt try anything your self on a motor you value

[mach1stang]

do you know the name of that program?
cuz i am that hard headed and like to try stuff myself to try and learn.

I ported 5 carbs allready, added boost ports, made transfer ports bigger, ported the head and always got a huge gain in hp. I lighten my fly wheels too. Im adding a nother boost port tonight to one of my motors.

All I did was research on porting and did it and its not to hard.

[mach1stang]

yeah i mean i would hate to sound cocky here but if you mess things up you really fouled up some where, but also even the motor gurus had to learn from somewhere.

[400exrider707]

Originally posted by mach1stang
yeah i mean i would hate to sound cocky here but if you mess things up you really fouled up some where, but also even the motor gurus had to learn from somewhere.

I know, and Im not saying dont try it, just try on something you dont care about... just know that there is more to it than removing material to make it bigger, there are many different things that go into porting a head and doing it correctly.

Grab a old chainsaw their easy to port.

[mach1stang]

thats where the kazuma comes in, and i have the basic down it doesnt matter how air you coming in if you port is rough it is not good for air flow.

Originally posted by mach1stang
thats where the kazuma comes in, and i have the basic down it doesnt matter how air you coming in if you port is rough it is not good for air flow.

Thats why you use a grinding stone it keeps it smooth. I really dont think polishing is needed.

[mach1stang]

well grinding stones work good but when they polish it makes it smooth as glass.

[400exrider707]

well you dont want your intake ports smoot as anything, they should be left kind of rough to help atomize fuel...

Originally posted by 400exrider707
well you dont want your intake ports smoot as anything, they should be left kind of rough to help atomize fuel...

My intake i just left the way the grinding stone left it. For the exhaust port i polished it a little but not much. I dont think polishing does anything IMO.

[400exrider707]

Originally posted by nacs420
My intake i just left the way the grinding stone left it. For the exhaust port i polished it a little but not much. I dont think polishing does anything IMO.


have you had it on a flowbench? Even been in a boat that needed to be buffed on the bottom? Then buff it and ride in it after...

think of it like this... picture a car hood... half of it is waxed and the other half not ( the wax job would be like your polish job) now picture the water running down both sides.... everything moves faster over a smoother surface... polishing is just smoothing the surface....

[mach1stang]

polishing is really just for exhaust cuz that is waste now the intake needs to be like what 400 said a lttle rough.

Originally posted by 400exrider707
have you had it on a flowbench? Even been in a boat that needed to be buffed on the bottom? Then buff it and ride in it after...

think of it like this... picture a car hood... half of it is waxed and the other half not ( the wax job would be like your polish job) now picture the water running down both sides.... everything moves faster over a smoother surface... polishing is just smoothing the surface....

Yeah but you polish it but then you ride it and it gets full of carbon so wouldn't that wreck the point of polishing it?

[400exrider707]

Originally posted by nacs420
Yeah but you polish it but then you ride it and it gets full of carbon so wouldn't that wreck the point of polishing it?

Why do you think most of the carbon builds up there in the first place??? Sure some carbon is going to build up on it eventually, but it will be eaiser to clean, and you can always re-polish it..

[mach1stang]

yep you have a point 400

Originally posted by 400exrider707
Why do you think most of the carbon builds up there in the first place??? Sure some carbon is going to build up on it eventually, but it will be eaiser to clean, and you can always re-polish it..

Well I rode my stock motor before i ported it for about 2 hours and it was all ready all black with carbon. But thats my 2 stroke 4 stroke probably burn cleaner.

[400exrider707]

Here's some interesting reading to waste some time... it talks about the theory of decreasing port size to increase power... very interesting stuff....

http://www.mototuneusa.com/think_fast.htm


also just FYI this is where a lot of atvriders members get their info for their break in on new engines... read that too if you get a chance...

[mach1stang]

yeah but they would have to be like straight threw but he may be right if have a huge exhaust port and a baby header you get torque so he may be on to somthing.

[400exrider707]

Originally posted by mach1stang
yeah but they would have to be like straight threw but he may be right if have a huge exhaust port and a baby header you get torque so he may be on to somthing.

No, and No, go read it first, the smaller ports increase velocity...thus the name velocity porting... read it!

[mach1stang]

yeah i know kinda what he is talking about it is like a turbo almost all the air is forced threw at a higher speed than with a big port. good find by the way

So on my motor I should make the port smaller? How? JB weld?

[mach1stang]

no i dont think that would work but it may be diffrent on quads.

[quadgod440ex]

You need a flowbench to port anything if u want it done right . You might be able to do it out of ur garage and think it is easy and right , BUT to do it right send it to someone . You can always port anything with a dremel but doesnt mean its gonna be right. I use to mess around porting heads on little go carts and mini bikes and stupid things like that , but i would never port my quad head or my car head .

[mach1stang]

yes you do need a flow jet to get it right but you can also make a improvement with out a flow jet ya know what i mean.

[JasonP]

Originally posted by 400exrider707
Here's some interesting reading to waste some time... it talks about the theory of decreasing port size to increase power... very interesting stuff....

http://www.mototuneusa.com/think_fast.htm


also just FYI this is where a lot of atvriders members get their info for their break in on new engines... read that too if you get a chance...

I would read this and come up with your own opinion on HV porting.
http://www.popularhotrodding.com/tech/0610phr_cylinder_head_porting/velocity.html

[sc400ex_rider]

http://www.popularhotrodding.com/enginemasters/articles/hardcore/0412em_porting_cylinder_heads/

http://www.cyclechaos.com/wiki/How_to_port_your_Engine

[chad502ex]

I hope I'm not too late... better late than never...

I cringe when I see this,...

MATH- know math before you port

engines make power based on mathmatical predictions.

main factors governing flow through a port are:

cross-sectional
taper angle from largest opening to smallest diameter
length of runner
short side radius
bowl blending
shape

however, that is just port; then you must consider valves...


valves are the restriction in the path


the most important area is one inch above and one inch below the seat.


flow can actually decrease if effective valve area to cross-sectional ratios get all out of wack.


if your gonna port yourself; do yourself a favor and just cleanup...


just cleaning up the port will help..


removing cast marks, bowl blending, compression chamber shaping, unshrouding the valves are easy enough for dremel operators to perform.

leave the port shaping, high velocity porting, sewer pipe porting to the experts that have velocity/cfm verification tools.

[400exrider707]

Originally posted by chad502ex
I hope I'm not too late... better late than never...

I cringe when I see this,...

MATH- know math before you port

engines make power based on mathmatical predictions.

main factors governing flow through a port are:

cross-sectional
taper angle from largest opening to smallest diameter
length of runner
short side radius
bowl blending
shape

however, that is just port; then you must consider valves...


valves are the restriction in the path


the most important area is one inch above and one inch below the seat.


flow can actually decrease if effective valve area to cross-sectional ratios get all out of wack.


if your gonna port yourself; do yourself a favor and just cleanup...


just cleaning up the port will help..


removing cast marks, bowl blending, compression chamber shaping, unshrouding the valves are easy enough for dremel operators to perform.

leave the port shaping, high velocity porting, sewer pipe porting to the experts that have velocity/cfm verification tools.


It's never too late, because Im sure other people will or have already had questions on the subject. Thanks for the info.

[mach1stang]

Originally posted by 400exrider707
Here's some interesting reading to waste some time... it talks about the theory of decreasing port size to increase power... very interesting stuff....

http://www.mototuneusa.com/think_fast.htm


also just FYI this is where a lot of atvriders members get their info for their break in on new engines... read that too if you get a chance...

sorry to bring back up such an old thread, but this is still eating at me, i was doing some porting today (because i am getting a new quad YAY, so now i have a crappy crapzuma to try this out on) and i just did the intake it is a twin cylinder so it goes from one carb to then to two, but what i did was just cleaned up all the crap in the intake, and then where it curves theres alot of uneeded material, i took the grinding stone and took some of that material out so now the air goes in alot smoother, but now the darn thing wont stay running could it be getting to much air and not enough fuel?