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holley power valve

BIGSHCLUNK

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Is there a big difference in a "high flow" vs a standard power valve? I'm talking street use not the track.
Thanks
BIGS
 
The high flow simply flows more fuel at full throttle.Might even be able to use less jet.Just get the high flow after a vacume reading to verify exactly what size PV you need:blob1:
 
I'd say it depends on the size of the PVCR's and if your engine demands the flow. Mild street engines can get by with the standard stuff as long as it's genuine Holley. Race calibrated carbs like a 700 DP (4778) will tend to have smaller PVCR's but make up the difference with larger jets. This is why they are not really good OEM replacement carbs.
 
Your right Meep:headbang: The high flow allows for more flow,but only what the PVCR's will flow so it won't hurt.:booty:The plug reading at the track will tell the tale:blob1:
 
Your right Meep:headbang: The high flow allows for more flow,but only what the PVCR's will flow so it won't hurt.:booty:The plug reading at the track will tell the tale:blob1:
To answer your original question: Use standard Holley replacement power valves, in the correct vacuum value for YOUR STREET MOTOR. Your wallet will thank you in fuel saved.
 
Hmm, I'm thinking standard, this car wont see any track time. Just the occasional blast! BTW vac is 12ish,,, so I'm thinkin 5.5...right?
 
I called Holley on this about my 4150 double pumper. I was told that only certain race type carburetors came with the high flow and that I should be just fine with the standard flow and wasn't even asked about my carburetor list number or motor so I said okay and did just that. I haven't had any problems. 12/2=6 so 5.5 should be fine. I used the same calculation for my car and I guess it is working fine. I think the main problem with gas consumption is from those squirters pouring fuel into the motor every time I move the pedal.
 
The standard flow should work fine for a non 4500 carb unless your running alcohol.
The power valve restrictions are much smaller than the power valve port window.
The Quick Fuel Hi-Flow power valves are $6.62 from Summit Racing.
 
I'm not sold on the Half manifold vac at idle theory. I know Holley gives this as a rule of thumb, but they also used to say 2" less than manifold vac..... I have used this practice in the past and had good luck, but the true way is to measure the exhaust gasses to define how rich or lean you are when stomping the throttle from start, placing load on engine from regular cruise speed, wide open throttle at RPM, and just easy cruise no load. This paints the picture of how the power valve is working in your application. You might find lean conditions followed by rich conditions throughout these tests when the PV does not have the correct Vac rating.
This is especialy true for street engines that see little time at the race track! Our race versions might not even have a power valve in the rear and jets larger to compensate on that metering block.
I read a post in the Holley forumns recently regarding this very topic, and the Holley employee that commented on the issue agreed to this type of tuning in regards to pv's.
You could do similar using just a vac guage ran from manifold to the passanger compartment and read the guage while crusing down the road at highway speeds. You wouldn't need the PV open at this time but when you place a load or have WOT you do.
Your ears can tell you when the engine is loading and also the position of your throttle.
 
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