Re: One Rich bank, one lean bank.
Ok I'll take a stab at it. So let's a assume the motor is running perfectly, perfect carbs, good temperature, good compression, good recirulation system, etc...... So why is one bank richer than the other? First the factory trys to make the air flow though the block the same for all cylinders, same intake shapes, same crankcase shapes, same reeds, etc. This would then indicate that they can use the same size jets in each carburetor and all cylinders would burn the same, but the problem is that each set of rings seals a bit differently to each cylinder, creating slightly different crankcase pressures (both positive and negative) as the piston movers up and down. This causes a change in airflow across the carburetor this causes a change in fuel flow through the jets. Now you have 4 cylinders with the same carburetor jetting all burning a bit differently. The factory simply jets for the richest possibility, some cyinders run perfect, while some run a tad rich. You could rejet and make it run a bit better, but probably not worth the time. Ok, so now what about the rich and lean from bank to bank? ( the original question). Crankshaft rotation is the answer. The crankshaft rotates clockwise, and on one bank of cylinders the rotation of the parts improves fuel and air movement, on the other bank it hinders it. So one runs rich and one runs lean. Here again the factory jets for the richest posibility.
