Okay, let's go over this....I see that you went a good bit further in some ways....
First, did you use an aluminum oxide stone?
Then, you also went into the valve cavity where I was too worried about bumping my grinder on the valve seats. Hmmm. I might rethink, but then I also need more length on my rotary tools so that I can see where I am going.
As for the exhaust, I notice that you radiused the lip of the exhaust. Was there any particular reason for that? Or were you just wanting to remove as much as you could? I am more worried about opening it greater than the total valve area.
I may go back in here for another look. Need to measure the total valve area, I think. Then I may get some more stones and felt wheels.
As for the polishing the intake...There are a couple rules of thought on that.
- One is that roughness increases atomization, which is true but you reach a a point where there is a trade off.
- If you think terms of in fluidics, roughness also puts frictional losses on the flow, and that drag will separate droplets. If you reduce the friction then the velocity will increase.
For my money, I think it will be better to have the highest velocity at the beginning of the intake, which is the smaller diameter. Then as it the fuel charge gets closer to the valves and splits, the area also gets larger which causes a drop in velocity. Then in this rougher area, roughness might actually cause more of the turbulent effect that you want.
Just think about water droplets on your car. When it's clean and waxed they run off. When it's dirty they don't. Roughness also gives them something to stick to.
AND OF COURSE...we are talking about thumpers. This isn't an engine that has multiple pistons and therefore creates anything similar to a steady flow at either the intake or exhaust. In between suck and blow traffic comes to a stop