4age bigport head: port & polish

[BenR]

No, total quench depth with the deck height and gasket thickness is 40 thou (0.040) or 1mm.........since 1mm is 0.040, that makes 0.5mm = 0.020"......not 0.012"

And when you account for rod stretch, i am talking about using steel rods and forged pistons, not OE items as they are not good enough.

As for your port questions:

1. You can alter the port inclanation, but you will see no benefit for the massive cost required. The 4age ports are already too big for such a small valve so you have no problems flowing enough so long as you do configure the port and valve seat correctly. If you do alter the port inclanation, you will have to spend time developing new valve seat profile and the back of the valve head will have to be of a different shape. And current trends at the moment are not to have high angle ports, but the highest flowing heads from Honda and the likes, have a generous short side turn.

2. Cutting is fine, it does shorten lifespan a little, but nothing too crazy. I prefer to install bronze guides and shape them correctly, you do not loose flow by having the guide protruding. A splitter design is bad, flow does not like to meet a sharp edge as it causes turbulance, shearing and absorbs energy.

3. The idea is flawed since the exhaust port is a high-low pressure setup with ever expanding volume gas due to heat, there is no suction direct and time is better spent working on anti-reversal properties. Use the header to tune pulses for scavenging effects or 'pulse tuning'.