I have some questions on power valves. I want to try and get a little better fuel economy while at cruising speeds by keeping the power valves closed until the motor goes into a boost condition. I have a 604" blower motor with Holley 850's (boost referencing disconnected) with mechanical actuated secondaries. The latest activating power valves that I can find are 1.0 HG but that should still allow them to stay closed longer than the current 2.5's in the secondaries and 4.5's in the primaries that I have now. I have the following questions.
When in a cruising condition on the primary jets only (around 3000 RPM), will the secondary power valves open once the motor gets to 2.5 HG vacuum even though the secondary butterflys aren't open and add extra fuel? Or would I have to have the throttle open enough to open up the secondary butterflys for the secondary power valves to open once I passed the 2.5 HG vacuum zone?
With the 4.5's on the primary and 2.5's on the secondary side, I think that means that the primary power valves will almost always be open at even a very low cruising speed and then the secondary power valves will open up around 50 mph. I'm thinking of replacing the secondary power valves with the 1.0's so hopefully, I can get up to around 60 (or maybe 70) or so before they open. I'm also thinking of then moving the 2.5's over to the primary side and replacing the 4.5's. Do you have any thoughts on trying this to see if I can improve fuel economy at cruising speeds? I currently run jet sizes of 85 on the primary and 90 on the secondary side. If I do change the primary side power valves from 4.5 to 2.5 will I have to increase the jet size to compensate?
Thanks in advance for any input. RR