Soldering the power valve shut for better gas mileage

[Anonymous]

I read somewhere that racers back in the days used to solder the power valve shut to prevent leaks in their race engines and also that power valves were good for nothing except for leaking and wasting fuel. Another guy did this on his car and is now getting around 24 MPG on a sixties ford van. What happens if you solder the power valve shut?? Wouldnt a heavy car going up a steep hill have trouble going up without the power enrichment system working?

What do you guys think? :

 

[CZLN6]

Howdy Tatao:

The answer to your scenerio is "Yes". Not only sluggish, but likely dangerously lean. The Holley power system is designed to include the extra fuel from the power valve.

The problem with racers and power valves was likely low vacuum due too long duration cams and too high of a PV setting. The solution is to choose a PV with a low enough setting so as not to open the PV, or, in some cases to plug the PV hole and jet up about 4 numbers.

Holley selected PV setting for carbs in specific vehicles and engine combinations so that the PV opened at the appropriate time. When we adapt and mix-and-match engines, vehicles and carbs it is our job to assess and tune the carb to the situation. 1st we have to know how the carb works. The PV is a vacuum activated switch. When vacuum drops below the rating of the PV, it opens allowing a meaured amount of extra fuel into the engine. Finding that "best spot" is our job as tuners. Too high a setting the PV opens too soon wasting gas. Too low a setting and the PV almost never opens, hurting performance and possibly causing engine damage.

Adios, David

 

[Anonymous]

Per Holley the sizing of power valves is based on vacuum at idle. Essentially you take your engine's vacuum reading and divide by 2. The answer is the power valve size you should be running (i.e. 15 = 7.5). Holley also recommends downsizing your main jets by 1 for every 2000 ft of altitude.

 

[rbohm]

8) the only reason us racers would eliminate the power valve in a holley carb is reliability. if it isnt on a race car it cant break and cause problems. that is also the reason you wont find vacuum advance units either installed or you find them locked out on a race engine. since fuel economy isnt the biggest concern in a race engine, they are jetted rich enough to prevent a lean condition from burning a piston.

 

[Anonymous]

Race cars are set up to run at full throttle. Street cars must compromise on the jets for cruise and full throttle. If you run the jets at a proper size for continuous full throttle then it will be way too rich at cruise speeds. Thus, you jet the carb for cruise speed and use the enrichment (power) valve to make sure that it doesn't go too lean at WOT.