The Super Duper Haggis Hauler

[ibrown50]

Heads look cool Bill

The general rule of thumb is that dual plane manifolds with a split chamber (like the one in the picture above) are better for street engines (they make better torque/ power at low revs) and single plane are better for race engines as they are better at high rpm.

But of course it's much more complicated the that and heads camshaft etc all have to be considered in the mix. I ran a 9 second car with a dual plane!