How Can Dual Exhaust Ports Be Made Into A Genuine Performance Option For 2 Valve Heads?

[Geoff2]

I think it was Rudge that first used twin exh ports in the 1930s.

[blown265]

For reference, here's my modified engine- the standard layout is the same.
Regards
Paul

[Dan Timberlake]

biological organisms prefer symmetry.
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hmmmm. I only have one exhaust port.

Then there is this, which about half the human population under 24 actively "prefers" about 18 times per day.
https://visualsonline.cancer.gov/retrie ... format=jpg

https://www.psychologytoday.com/us/blog ... -about-sex

[CamKing]

Consider the possibility of a wider power band if the pipes are different length.

I can hear my dad now: "great, now no matter what RPM the engine is at, at least on of the pipes will be the wrong length."

[dannobee]

That seems to make sense. However, what doesn't seem to make sense is that other air cooled four valve designs don't suffer any overheating problems. For instance, the Suzuki DR650 and 800, the Suzuki LS650, the Yamaha XT600 - 660, the new Harley-Davidson Milwaukee-Eight Vtwin, and the Polopolous Porsche flat 4 are all in continuous use without blowing up or melting down. I could go on with many other examples. What's going one here?

Doesn't the HD Milwaukee Eight have coolant flowing around the exhaust ports? The Polo engine that I've seen first hand was based on a Porsche 911 engine and two valve. If you have pics of a working 4 valve Polo, I'd love to see how he does it.

The others are big singles, and even with lots of fins hanging out in midair they still have their fair share of cracked heads, usually around or between the exhaust ports. Or the heat causes the exhaust valve guides to wear out.

[Tuner]

Consider the possibility of a wider power band if the pipes are different length.

I can hear my dad now: "great, now no matter what RPM the engine is at, at least on of the pipes will be the wrong length."

Classic example of "is the glass half-full or half-empty" and "you can't win for losing".