Lets See Your Porting.
- Thread starter roccosbike
- Start date
- Tags porting.
Here's the porting I did myself on my Briggs 7hp block.
I used a 3/16" diameter carbide tree burr in a high speed air grinder to shape the pockets and ports and then polished them up with a 1/4" slotted rod with cloth backed sandpaper rolled around it, powered by an die grinder. I felt the intake port turned out too slick, so a six second shot of aluminum oxide in the blasting cabinet was used to give it a nice satin finish.
As you can see, compared to the before picture, I took quite a bit of meat out of the ports. Hopefully I didn't overdo it on the intake and lose my bottom end velocity. (looking for a big wheel trailbike to put this motor in)
Bob
I used a 3/16" diameter carbide tree burr in a high speed air grinder to shape the pockets and ports and then polished them up with a 1/4" slotted rod with cloth backed sandpaper rolled around it, powered by an die grinder. I felt the intake port turned out too slick, so a six second shot of aluminum oxide in the blasting cabinet was used to give it a nice satin finish.
As you can see, compared to the before picture, I took quite a bit of meat out of the ports. Hopefully I didn't overdo it on the intake and lose my bottom end velocity. (looking for a big wheel trailbike to put this motor in)
Bob
That's true, but the main reason is that there is a small layer of air that is tumbling and swirling along the wall of the port. This is referred to as the boundary layer. A slightly rough surface helps to initiate the formation of the boundary layer. Air molecules can move past other air molecules with much less friction than along a metal surface, so once the boundary layer is established along the port wall, it allows the air in the center of the port to flow with much less friction, speeding flow into the cylinder.
Sorry. I'm kinda a tech junkie when it comes to motor stuff:surrender::laugh:
Sorry. I'm kinda a tech junkie when it comes to motor stuff:surrender::laugh:
You have thos pop up on your post.
General Electric IEC Combination Starters with NEMA 4X enclosures exclusively from Grainger
Why?
General Electric IEC Combination Starters with NEMA 4X enclosures exclusively from Grainger
Why?
Yes shortened guides wear quicker.
There are a couple of things you can do....
You can push them provided you lift allows ( literaly push them out of the port and up under the valve spring ). But this can cause trouble too if they continue to move and come loose later.
Of you can leave them and simply taper and thin them as I do.
The head shown above is for a very modified clone.
You will not need to go to that extreme with stock valves.
Just a mild clean up is all you need.
There are a couple of things you can do....
You can push them provided you lift allows ( literaly push them out of the port and up under the valve spring ). But this can cause trouble too if they continue to move and come loose later.
Of you can leave them and simply taper and thin them as I do.
The head shown above is for a very modified clone.
You will not need to go to that extreme with stock valves.
Just a mild clean up is all you need.
