[GTO Karl]

Since a couple people tried to answer my question. Here is the answer:

The power valve is the power enrichment circuit of the Holley carb. It has a calibrated orifice that is the same size for all model carbs. They just come with different springs to cause them to activate at different levels of vacuum.

Once you have tuned your car for max full throttle performance (using your jets), you have effectively created a air fuel ratio that includes both the fuel from the jets, and the fuel from the enrichment circuit.

This ratio for max performance is always going to be on the rich side, relative to what you need for part throttle, light load operation. If you want to lean your carb for part throttle operation, you would need to change the jets, thereby changing your max performance settings. You could increase the secondary jetting and just lean the primary. But usually you only want to experiment with this to try to improve perf.

The solution is to lean the primary as far as you can to increase your fuel economy and throttle response, then drill the orifice in the power valve larger by the difference in the full power and cruise jetting.

Now you have a lean cruise and a tuned, full power enrichment circuit.

It would have been nice if this problem had been addressed in the redesign that created the Demon series of carbs.

This is why metering rods exist and are so effective in there job.

The only reason I brought this up, is because, it is something I rarely here anyone talk about, and yet, it is one of the most fundemental things you should know if you run a Holley or Demon carb.

This includes race or street. Personally, I want my fuel curve to be correct while I'm doing my burnout, driving down the return road, cruising through the pits, everywhere. It will keep your plugs from loading up.

And if someone is going to give me advice about which carb I should use, they should know these things. Also, I would want to know whether they recomend a carb series with straght boosters, dogleg boosters, or annular discharge. Which throat and butterfly size might work best and why. There are so many different Holley and Demon carbs to choose from...it is very important to know which one to spend your money on and have some idea as to why.

The engine doesn't care how the fuel and air arrives. Metering rods, power valves, injectors, jets, Rochesters, Holleys, or Flying Toilets... All it cares about is the mixture ratio and quality, and that the device is not a restriction to the required quantity.

I'm going to keep experimenting with all types of carbs and injection, because I think it is fun to tinker and educate myself. But I will continue, for the most part, to run a Qjet on my bracket car, because people say you can't, because I like the way they work, because the money for a Demon carb can make HP somewhere else.

Karl