So far so good.  The valves are out of the head

Oh, and I forget who asked, but I believe that the paint on the valve springs is supposed to indicate the top of the springs when installed.  All 8 of them are that way.

Kropatchek wrote on 12/31/69 at 16:00:03:

Oh well, I thought that it made sense since the paint marks were all up...

Yea, there is nothing a satisfying as cutting for a while and then suddenly remember that you were supposed to check the spec's before starting.    

Then you find out how really good you are when it comes to "seat of the pants flying" with the cutting  tools.  

So far, I am out to 1.492" on the outside edge of the port.

I have not lapped the valves yet.
I think I will go ahead and have a nice 3 angle job done on it when I take the cylinder in for a shave.
Clive worked out some numbers for me and suggested that I limit the shave to about 0.050" in order to leave room for the valve-to-piston clearance.

There you go Clive.  You've been wanting me to do it for a couple years, and I finally got around to it

Opened the exhaust port up 2 MM to 36 MM and ground as much of the rough casting as I could reach...I didn't want to try grinding through the valve seats in the event I got careless

After grinding I used polishing compound and felt wheels.



Here's the head turned over.  There isn't much more metal at the top of the port.



Then I went back the intake port that I worked on a little bit 4 years ago.  More polishing.  See how rough the casting is up near the valve guides?  That's the way the whole port used to look like.



And then because I still had a bunch of compound and felt, I decided to clean up the combustion chamber.  No grinding, just polishing.  A lot of it.

I'll lap the valves and seats next...



PS - something about the way the photos get resized, makes the edges of the exhaust port look rough.  They aren't....I sure do wish they'd let photos display 640 pixels wide...

Great to see you guys doing the port work and hope it works out for you.
Go well.
Clive W  

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