Hey everyone: I adjusted rear brakes, because they were dragging, and advanced the timing a few degrees before TDC - she now rolls better, and has much more pickup. I think that was most of my low power issue...Once I added some advance, the vacuum test was steady at 18in. or so. It didn't slowly creep down, so I don't think the muffler or exhaust is restricted.
But, I did find that the heat riser is completely seized, probably in the closed position. If I remove the carb, can that flapper be removed from above the exhaust manifold? Or, do I need to buy a new manifold?