delirium trigger
Active Member
cb350, wanna do i minor port on intake and minor port and polish on exhaust. any one do it themselves? any tips or things to look out for? whats the best most excessable tool for the job?
minor port and polish with a dremel? yes?no?
- Thread starter delirium trigger
- Start date
Two schools of thinking... some folks keep the intake a bit rough to use the turbulence to help keep the fuel atomized while others smooth it out to increase intake velocity and rely on heat to do the job.
For the exhaust ports, I'm not sure. I would guess it wouldn't make too much of a difference as you'll be getting build-up there pretty soon anyway?
For the exhaust ports, I'm not sure. I would guess it wouldn't make too much of a difference as you'll be getting build-up there pretty soon anyway?
If you're going to do it do yourself a favor and pick up a die grinder and some long shank burrs. Most die grinders are pneumatic but there are electric ones too. If you use an electric one you have to make sure its got enough power. I have a Makita GD601 and its 3.5 amp motor is adequate to do the job so any other brand with about the same power draw or more should handle it for you. You've pretty much got to get long shank carbide burrs for the work; they won't be cheap, but as long as you don't bang them around they will last a very long time.
Start by reading every article or book you can get your hands on about port design and porting. AG Bell has an excellent book on 4 stroke preformance and David Vizard is another good source of material.
We have die grinders and carbide bits and for a small motor clean up, a Dremmel is actually enough for the task. If you have a flexible drive that helps and it will never have the power of a real set of professional porting tools but for a one off, you are probably better with something less likely to get away from you.
The issue of polishing is all relative. Some argue that a polished exhaust slows down carbon build up and others argue that you need that carbon to keep heat out of the head an in the pipe. on the intake side, it's pretty well accepted that you don't polish ports for several reasons, but they need to be 'sandpaper smooth".
Stay away from the valve seats and clean up obvious bumps and casting flash but try to avoid making the holes any bigger than stock. You need to keep velocity up in a port and big holes hurt that and they hurt flow. Bigger ports only make more power if they are the right shape and if they were the restriction.
A light clean up won't hurt much and might even help. Get a good valve job will do more for you than an average port job.
Don't try to make it the same diameter all the way down. Ports need a very special shape around the bowl and Hondas used to have a Cricital port diameter that was typically too large for other port dimensions.
We have die grinders and carbide bits and for a small motor clean up, a Dremmel is actually enough for the task. If you have a flexible drive that helps and it will never have the power of a real set of professional porting tools but for a one off, you are probably better with something less likely to get away from you.
The issue of polishing is all relative. Some argue that a polished exhaust slows down carbon build up and others argue that you need that carbon to keep heat out of the head an in the pipe. on the intake side, it's pretty well accepted that you don't polish ports for several reasons, but they need to be 'sandpaper smooth".
Stay away from the valve seats and clean up obvious bumps and casting flash but try to avoid making the holes any bigger than stock. You need to keep velocity up in a port and big holes hurt that and they hurt flow. Bigger ports only make more power if they are the right shape and if they were the restriction.
A light clean up won't hurt much and might even help. Get a good valve job will do more for you than an average port job.
Don't try to make it the same diameter all the way down. Ports need a very special shape around the bowl and Hondas used to have a Cricital port diameter that was typically too large for other port dimensions.
dansofield550
Active Member
i done mine like this , smoothed out all the lumps and steps of which there were plenty , left it with a sanded emery flap finish on the inlet and a quick go over to smooth out in the exhausts
haplo_84
Been Around the Block
Yeah its like teazer and dansofield said, i know its from a car forum with log heads and push rods, but i had to go back and read alot of the real technical stuff. These guys get down to the real nitty gritty talking about thermactor bumps and the shape of the cumbustion chamber to help create that best flow in and out. Though that last part is a bit more critical to the inline 6 with the intake and exhaust ports on the same side cause the air flow has to essentially do a u turn inside the combustion chamber. If you have the head off cleaning and polishing the inside chamber will help you with not having any hot spots and preignition or knocking.
haplo_84
Been Around the Block
Here i found some good links, more car related but just as relative
http://www.popularhotrodding.com/tech/0610phr_cylinder_head_porting/index.html
and if your sight isn't perfect you may need to blow it up a bit.
http://www.mondellotwister.com/ArtHeadPort.htm
http://www.popularhotrodding.com/tech/0610phr_cylinder_head_porting/index.html
and if your sight isn't perfect you may need to blow it up a bit.
http://www.mondellotwister.com/ArtHeadPort.htm
delirium trigger
Active Member
i've read the a.g. bell book, im aware of the concept of removing casting lines and sharp corners and then u polish only the exhaust side not the intake. Bell sais that the original castings are usually terrible (and they are) so even minor work will reap results. im not scared to do the work im just not sure what tools are needed, i.e what i can use that i already have, like a dremel and a grinding wheel. im thinking about polishing the insides of all my custom exhaust pieces before i weld them too, any terbulence lost in the exhaust is a bonus, even large amounts in the intake is bad, u only want i minor amount of swirling just around the plenum walls to encourage the gas to stay vaporous and not pool into liquid.
