Got my Vaccum readings so what powervalve to use?
06-22-2003, 05:13 PM
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Got my Vaccum readings so what powervalve to use?
Im running about 15lbs at idle out of gear. In gear I'm running about 11-12lbs. What powervalve shoud I use considering these readings? The carb has 6.5 valves front AND rear. This is on a Holley 4010 750vac. secondary carb....Guessing that this calls for a 9.5 or 10.5 correct? 
BH
BH
06-22-2003, 06:53 PM
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Guess Im thinking of a big blower back there I'm getting them confused
Seems like I read somewhere here where someone recommended using a valve 2 INCHES Lower than your reading but I couldn't find it......
BH
Seems like I read somewhere here where someone recommended using a valve 2 INCHES Lower than your reading but I couldn't find it......BH
06-23-2003, 11:00 PM
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I have been experimenting with power valves lately myself. I ran a vacuum gauge from the engine, up to driver`s seat. I determined that engine idles at 15" in gear, cruises at 8" at 3500 rpm and dips down to 3" upon heavy throttle. I am currently running a 4.5" PV and it seems to work best for my (near) stock 454. I am running a Holley 800 double-pumper carb.
BTW: I have tried from a 3.5" to a 7.5" PV and I like the 4.5" best. Every engine is different, just try out different ones.
I would plug that secondary PV and add 6 to whatever jets are in the back right now. Just my .02
BTW: I have tried from a 3.5" to a 7.5" PV and I like the 4.5" best. Every engine is different, just try out different ones.
I would plug that secondary PV and add 6 to whatever jets are in the back right now. Just my .02
06-24-2003, 11:49 AM
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DON"T JUST TRY DIFFERENT ONe's ,,you'll have a melt down !!!
Also at wide open throttle it needs to be zero(or very very close) or you need a larger carb thats a test to see if its large enough !! 6.5 works on 90% of NA motors 4.5 is too low it would not open until to late
thus lean ,also your milage is tons better with the valve in the secondary side as it will open when needed and not just have 6 sizes larger jets going if the secondarys are just barley open
just my 1 cent worth
Also at wide open throttle it needs to be zero(or very very close) or you need a larger carb thats a test to see if its large enough !! 6.5 works on 90% of NA motors 4.5 is too low it would not open until to late
thus lean ,also your milage is tons better with the valve in the secondary side as it will open when needed and not just have 6 sizes larger jets going if the secondarys are just barley open
just my 1 cent worth
06-24-2003, 08:53 PM
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Several "So Called" Holley publications reccomend 2" lower than your reading at idle in gear.....I can't find anything at all about the secondary powervalve....Several days ago I sent a email to Holley about this question. I got their reponse today. They said to go 1/2 of my vaccumn reading in gear@ idle for the primary valve. For the secondary valve go 2" below my vaccumn reading at cruise(in my case 3500rpms). I realize these "tech" guys are not always correct especially in marine applications.....Since Im pulling about 11.5 at idle I will split the two reccomnedations and start with a 7.5 and work from there. I won't go any lower than 5.5 and any higher than 9.5 on the primarys.....I need to take anouther reading at cruise to make sure I get the correct reading for the secondaries.....This carb was installed by Crusader Marine on HP Big Blocks....Holley said stock it came with 10.5 in the primarys and 6.5 secondarys.....
BH
BH
