Looks like that cam has 298/308-degrees advertised duration which would put it at 83-degrees of overlap.
The overlap (point about TDC where both valves are open) is the end of the exhaust stroke and the beginning of the intake stroke. The scavenging affect of the mass of the exhaust gasses moving down the header primaries pulls on the intake and begins the intake cycle before the piston changes direction at TDC.
Too much overlap for a given application leads to reversion at all RPM. Primary factors that contribute to this include displacement and low-lift valve flow. This is compounded by two intake valves being open simultaneously with a single plane intake. The pressure in the exhaust can be much greater than in the intake.
Ideally, you want just enough overlap to evacuate the entire cylinder of exhaust gas and replace it with fresh intake charge. The problem is that at all other RPM below peak power (hopefully), reversion can and does occur to some extent. Some so bad exhaust stains are present in the intake manifold.
The blower will not produce sufficient boost to overcome exhaust system pressure at idle, where the blower inlet is restricted the most by a closed throttle. Only when the blower can breathe does it have potential to produce boost.
Using my combination as an example, I run wet through transom Bassett headers with a ball valve at the seat to turn the water to the primaries off. I do not restrict cooling water flow to the engine. Lastly, every drop of water that goes through the engine dumps into the collectors.
My engine pulses to about 2800 RPM and we idle it down to further accentuate the blower surge. It does not smooth out until after 3700 RPM.
With water-jacketed headers you won't experience the learning curve I had with the ball valve. Turn the water off BEFORE coming off plane with enough time for the pressure in the lines to drop.
Wet flow reduces horsepower. I would recommend restricting the wet flow to the collectors so there is only enough water (with a safety factor) to cool the exhaust hose. Dump the rest overboard so that flow through the engine is not restricted.
Restricting the wet flow through the collectors will allow you to achieve all of your objectives with the least loss of power and still strut the surge.
Good luck,
Joe
P.S. If you have a blower manifold that has water ports in the four corners, make sure that you have equal flow through both sides of the engine, and out of the timing cover end of the manifold.
