[Gregski]

Well its been a while since I updated and with the Holiday season behind us its time to get back into it. Today I replaced my 6.5 Power Valve with a 10.5 one. I believe that is the biggest one. Why did I do that? Well I noticed that I get incredibly high vacuum at part throttle, 19 to 20 inches of mercury I guess its called not PSI for vacuum. So as I am cruising around at part throttle say at 45 MPH I am pulling that much vacuum. The problem being when I give it gas my engine leans out to like 20 AFR way too lean and the car stumbles until it catches up on fuel

Now don't get me wrong vacuum is good, vacuum is the central nervous system of pre Electronic Fuel Injection (EFI) cars, however the Power Valve needs to be tuned accordingly.

So what the heck is a Power Valve and what does it do?

Well I heard it called an economy valve and I tend to buy into that nomenclature. The Power Valve is a spring loaded diaphragm helper a little assistant (see earlier Post #125). As you are cruising around at part throttle the car is not under very much load, its pretty easy to roll the car around once its rolling, somewhere I read it only takes like 25 horse power. You ever push a heavy something and once it started rolling you could just keep pushing it with one hand. Well same idea here.

Anyway there you are cruising around and all of a sudden you give it more gas to speed up for what ever reason, maybe you are on a freeway onramp and need to merge into traffic. What happens in the carb? Well the butterflies fling open and a ton of air rushes into the carb. But wait what about the gasoline? Well air moves much faster than gas, so your carb goes lean, way lean until the gasoline catches up.

So its the Power Valves job to flow more gas and what tells it to do so is vacuum, more precisely a drop in vacuum. The numbers on the Power Valve tell at what vacuum the power valve will open. So as my vacuum drops from 20 to 19 to 18... I had to wait until it dropped to 6.5 before my old Power Valve would let more gasoline into the intake manifold. Now I only have to wait until the vacuum drops to 10.5

I think the reason that the Power Valve is dubbed the economy valve is that its like a gatekeeper it prevents too much gas flowing through when you don't need it (cruising) and more to flow through when you accelerate but based on the vacuum signal and not your right foot.

The Accelerator pump reacts to your foot if you mash the pedal it will squirt, if you gently press your gas pedal slowly down to the floor the accelerator pump may not even squirt at all, yet when the vacuum drops beyond a certain level 6.5 or 10.5 that Power Valve is opening.

hope that makes some sense, please correct me if I am wrong