port matching

[jethrobolas]

Anybody have experience with cleaning up the ports in the heads and matching the intakes to the heads? Carbs are off for various reasons and installing Sean's hd oiler. Wouldn't be too much work or money to pull the heads and get the little grinder out.
Question is, would it be worth it? I have 4-2 holeshots btw, so flow won't be much issue at that end.

 

[alorio1]

I have always heard the term "ported and polished" and watched an old mechanic do a 2 stroke back in the day when Yamaha only made 2 strokes. So if you are going to port, I would suggest polishing, because the engines he built really put out more HP....

 

[Fire-medic]

I have read in Kevin Cameron's columns that the polishing may not be the best way to approach porting. He said the slightly rough texture of the intake walls helps to promote better mixing of the intake charge due to the gas/fuel mixture 'tumbling' as it passes-along the intake.

There is the comment made that 'polishing sells port jobs, because that's what the customer likes to see, even if it doesn't help the airflow.'

Sorry, I am not a tuner or a professional mechanic, I cannot claim any real personal experience from doing a porting/matching. Supposedly, things that you think would help 'move air and fuel' like large-diameter passages, actually hurts the overall performance where engines operate 98% of the time. It may help generate more-flow at close-to redline rpm's, but how-often do you spend there on your bike, unless it's a racebike? Keeping the velocity of the incoming charge up is more-important over the typical rider's rpm range of usage, than is cramming into the cylinder head the most fuel/air at the highest rpm.

 

[Traumahawk]

That is probably a "Sean" question...and hopefully he will answer in the morning.

 

[V4ever]

Most airflow improvements usually come from the valve seat area and possible shaping around the valve guide areas, as far as polishing, like was said earlier, too smooth of a surface will actually create a layer of "dead" air along the surface that can hurt airflow and also let fuel drop out of suspension. With out a flow bench I would be conservative with a grinder.

 

[thor_eyerdhal]

I port matched the intakes with the heads and Vboost butterflies with intakes.
No polished intake ports, as said before => layers of slow air

 

[one2dmax]

Exactly. Matching the intakes up is just fine but don't expect to find 10hp there. Don't polish the intake side as noted. You can polish the exhaust.

 

[sdt354]

I've found vmax intakes to match well, but exhaust to be off quite a bit. I wouldn't remove heads just for port matching. Like Sean said, it's a small increase. Nothing to loose if the heads are off already. Unless you get too aggressive with the grinder. Long sanding cones from H.F. work well.

 

[jethrobolas]

Well, if it's not something I will notice I don't think I will bother. Already have the carbs off and was looking in the intakes and noticed some small casting boogers, also the transition from intakes to heads isn't very smooth (kind of a little step where they mate). If it won't register any difference on the butt dyno, I'm not pulling the heads.
I am aware of the boundary layer effect that a shiny polishing job would destroy. Just looking at the uneven transition between head and intake as well as the pimples in the runners.

Thor, did you notice a difference? Stronger pull at top end wot?

 

[thor_eyerdhal]

No, it should only give better feeding at high WOT RPM when my buttOmeter is shutted down rerouting all power in my arms and eyes

I think i may be noticeable on Dyno or Chrono..

 

[jethrobolas]

Ok. Probably not worth the effort. Thanks for the input everybody.