In this session, we decided to tackle how to adjust and tune secondary opening rate for a vacuum-operated Holley. Vacuum secondary Holleys are easy to identify because of the large diaphragm ...

The power valve should not open until vacuum drops below that stamped on the valve (i.e., if the power valve is stamped "65", the valve should not open until vacuum falls below 6.5 inches Hg).

Next, install the spring in the lid and gently align the lid to the base making sure all four holes in the diaphragm are aligned. Next, apply a small amount of WD-40 or silicone spray to the ...