Porting

[Stuart Giles]

Not worth doing a lot of work on the ports unless you have decent carburation and exhaust; factory valve springs won't go any/much over 5000 RPM either. As Alan says, getting a really decent shape in the valve throat -the biggest restriction in the port area- really involves increasing the valve size. If you do any work on the inlet ports, the "short side radius"  -which is actually a sharp right angle on factory blocks is where the bulk of the flow happens, so is the best place to be concentrating on. This is a block I did some work on where you can see that there is now a short side radius rather than a near knife edge right angle at the valve throat.