Velocity porting vs. Oldschool porting

[speedy400]

Hey I just got the head of my 82gs850. I am prepping for my cams coming in later this week. I have done over a dozen old school port jobs, (bigger, smoother, velocity, ext.) but only one of the new school velocity port jobs. If you've never heard of it, heres a link.- http://mototuneusa.com/homework.htm -
Well I know for 4 valve per cyclinder, velocity porting has almost proven better, but 2 valve per cylinders like my 850, questionable. What do you guys think? Also one extra question, for our 4 cylinders, how much would bumping up the compression 1-1.5 lbs help? Thanks!-darren

[speedy400]

Well i'm in the process of porting her at the moment. I decided on just a basic clean up job plus. Port matching, casting flaws, and edges will be taken care of. I still want to hear some opinions if you guys got em about the subject. Thanks-darren

[pano]

I don't have enough experience to give you an opinion either way but I have an 1100e head that has some fins broken because of an accident. In the future I may try the new method to see how it works out.

[nastyjones]

well, on my old school gs1000 dragbike, my engine builder told me the real secret in these 2-v engines is in the head. Smoothing & porting & polishing is one thing but at least as important is the valve job. He machines the head to install larger racing valves, then does a special 5 angle valve job. He wouldn't tell me all his secrets, but with these mods plus cams & Lectrons the bike put out about 170 hp, good for low 9 second passes. I wish someone would walk us gs'rs through a p&p with pics of course. It would be very valuable to many of us I'm sure.
Is anyone listening????????????

Paul

[Addy Leung]

I do not have much experience but have some research.
This link may really give you some basic idea of engine modification about the head, intake and exhaust.

http://www.headerdesign.com/extras/engine.asp

[Mysuzyq]

Check Bob Bertaut's site, for great info, with photos of velocity porting plus a bunch of other mods you might like to try.......he knows whereof he speaks. Mad respect for these guys who are'nt afraid to share info.....

http://www.bertaut.com/gssuzuki.html

Tony.

[fat_sac]

170 horses? That's nuts. How much has anyone seen in the 750's? I'm doing an assload of work to my top end. Just wondering if anyone has suggestions since you're on the subject.

[Mike_H]

Hmmm...spent a little time checking out the first site posted. This "new" way of thinking is interesting. He is essentially increasing pressure, which will help get more air in. Works kinda on the same idea as turbo charging. More pressure = greater volume of air/fuel mixture=more power. You can also do the same thing with intake runner lengths, but that is RPM dependent (enter iVVT-i and V-tech). I also know that engines are designed for turbulent flow (aids cumbustion), and decreasing the diameter of a port will help that. You can also gain power from "old school" porting, which will help the flow side of the equation (less "resistence" to flow, essentially like bumping the current to a electric motor...) The problem is one of diminishing returns though. Eventually, the restriction to flow will start to asphixiate the motor, and you will see a drastic decrease in power. The webpage sounds too good to be true however, and I believe that the truth is probably somewhere in between. My 0.02

[fat_sac]

Here's my .02.
You can see the blowback evidence in any motor when you look down the runners. Why on earth would you close any intake up? If you're getting soot in your runners, it's just as easy and more efficient to open the exhaust. There needs to be a careful balance between intake and exhaust. Closing the intake on a high output motor just seems silly to me. WAAAAY silly.

There's also no reason to worry about the wall's smoothness when there's stuff out like fuel heaters. You wanna see a nice little gain in HP? Put a fuel heater on your ride. Hot gas atomizes quicker and much easier than cold fuel. The article talks about the epoxy 'insulating' the fuel from the engine heat. You want the air cold so it's dense, but cold gasoline is very inefficient. So if that's the case, why would you want to insulate it? I know every builder has his/her own ways about doing stuff, but I'd NEVER follow this guy's lead.

[speedy400]

Well the point of the wedge shape in the intakes isnt for no blowback, its for velocity, to get the mixture moving as fast as you can right before it shoots in the combustion chamber, so it practically forces its'self in as much as it can. But I think the 2nd link^ the guy really got it right, open up the intake ports via porting old style, then velocity epoxy it. That way youd have the big cc port flow of old style yet the velocity of the epoxy porting. This'd be quite a lot of time and effort though.-darren

[fat_sac]

Well the point of the wedge shape in the intakes isnt for no blowback, its for velocity, to get the mixture moving as fast as you can right before it shoots in the combustion chamber, so it practically forces its'self in as much as it can. But I think the 2nd link^ the guy really got it right, open up the intake ports via porting old style, then velocity epoxy it. That way youd have the big cc port flow of old style yet the velocity of the epoxy porting. This'd be quite a lot of time and effort though.-darren

That makes more sense. Isn't high velocity for torque though, and short runners for top end? He also talked about road racing applications. I'm building my motors now for high RPM's. I don't see why he'd worry about velocity with a motor that's gonna spend it's mojority of time skimming the rev limiter.

BTW, your sig? I want to know about your bike. I always like to see new GS's.

[speedy400]

Heres a link for pics of my baby -

http://www.thegsresources.com/_forum/showthread.php?t=88207

I'm not really sure why for road racing aps itd really help(when you boucing off the limitter) but I suppose you gotta get up to the rev limiter some how, so I'd suppose it'd get there really fast:? . I'm not too sure.-darren

[KGB]

I did a 3 angle valve job and decked the head on my 1000S
many years ago.
Jetted the carbs and run a V&H 4>1 pipe.
Breathes well and runs well.
I also went 20 over on the rebore.
Otherwise it's "stock"

[speedy400]

How much did you have it decked? Thanks-darren

[nastyjones]

Does anyone have any pics of the porting job on a 2-v motor while they were doing it?

Paul