Just to be clear, the PV opening point is not speed dependent, it is manifold pressure (i.e., vacuum) dependent. A PV with a larger number (e.g., 85) starts to open at a relatively high manifold vacuum, in this example 8.5"hg manifold vacuum. A PV with a relatively low number (e.g., 35) starts to open at a relatively low manifold vacuum, in this example 3.5"hg manifold vacuum. Keeping the power valve closed as long as possible on accels and heavy cruises means using a PV with a low number (at the risk of possibly running too lean with a heavily loaded engine).
Just as an aside, the 390 we put on our 240 powered Anglia worked fine out of the box except for needing a much bigger pump shooter. But we were not trying to optimize mileage. That's what late model tuner DDs are for.
Last edited by THE FRENCHTOWN FLYER; 11/23/19 12:50 PM.
