raising and lowering ports

[Wild Knight]

Should you raise both ports or lower the intake and raise the exhaust when porting? Does it differ between race saws and work saws? If you would explain the theory of how, when and why you decide to raise or lower a port, I would greatly appreciate it.

 

[rickyrooster]

when porting a saw you should raise the exhaust and lower the intake. how much depends on what you are doing with the saw. you should widen both the intake and exhaust up to 70% of the cylinder bore or around .090 from the edge of the piston which ever come first.

 

[Meadow Beaver]

With your exhaust you can just widen, dechrome, and polish you don't really need to raise it for a basic job you'll raise without noticing anyhow.
Intake can just be lowered smoothed over, widen some and it can be left a little rough. Also if you want you can take the lip off the lower transfers and polish them up, other stuff comes in time.

 

[wigglesworth]

If the exhaust is raised, RPM increases, but torque decreases. If lowered, RPM decreases, but torque increases. I prefer not to raise the exhaust to keep RPM within the stock range which is usually +/- 1000. And I like torque

 

[Meadow Beaver]

You can do both or deck the cylinder.

 

[blsnelling]

I never raise the exhaust unless I have to to improve the shape of the port. I still typically see an increase of 1500 RPMs.