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Author
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Topic: Do I run a secondary power valve or not?
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f100cleveland
Gearhead Posts: 363
From: St. James, MN
Registered: Sep 2004
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posted 02-10-2005 11:05 AM
   
I am wondering if its a good thing or not to run a power valve on the secondy side of my Holley DP? Any pros and cons to this? It is mostly street driven. Thanks------------------
1982 Ford F100 2wd Shortbox. Powered by a 357 Cleveland w/ closed chamber 4v's and a Funnelweb. Full Roller c-6 trans with Gear Vendors Overdrive and 4.86 geared Detroit Locker equipped 9" rear. 1982 F100 351c 4v 1977 F150 460 Burnout Truck
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ted
Journeyman Posts: 75
From: Central Texas
Registered: May 2003
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posted 02-10-2005 11:38 AM
If the carb was not originally supplied with a secondary side power valve, then don't run one in the secondary side.------------------
Ted E.
Big inch Fords are plenty fast, but Y-Blocks's are fun when they run in the low 9.60's @ 135mph.
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f100cleveland
Gearhead Posts: 363
From: St. James, MN
Registered: Sep 2004
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posted 02-10-2005 12:11 PM
The originally came with it. I've since switched to a Pro Form main body and BG throttle plate. Just curious if its better to run one or leave it out. Seems that all the carb shops I've talked to have told me jetting recommendations WITHOUT a pv in the rear. So I'm wondering if they are getting at something by giving me the recommendations without.------------------
1982 Ford F100 2wd Shortbox. Powered by a 357 Cleveland w/ closed chamber 4v's and a Funnelweb. Full Roller c-6 trans with Gear Vendors Overdrive and 4.86 geared Detroit Locker equipped 9" rear. 1982 F100 351c 4v 1977 F150 460 Burnout Truck
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Ryan Wilke
Gearhead Posts: 2289
From: Stanton, Michigan 49707
Registered: Oct 2000
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posted 02-10-2005 12:27 PM
If you replace the rear or secondary power valve with a plug and then jet up accordingly, you don't need to ever worry if you've blown that PV. Many folks will recommend to increase your rear jets by 6 or 8 sizes if you switch to a plug for starters, then experiment from there as to what works best for your combo and driving habits.GOOD LUCK!
Ryan 
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ted
Journeyman Posts: 75
From: Central Texas
Registered: May 2003
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posted 02-10-2005 02:33 PM
Seeing as how your metering block originally had the power valve in the secondary side, which is what my 4781 850DP is like, then ideally it's best to remove the power valve. Hard launches can actually starve the power valve circuit if the power valve opening in the secondary fuel bowl is uncovered. The power valve opening actually sits higher than the jets so the power valve opening can become uncovered before the jets do.The correct procedure for sizing up the jets when removing a power valve is to determine the size of the PVCR (power valve channel restriction) using a set of number drills. Then take the area equivalent of the number drill and add to the area of the jet size. You can get the area of the jet size out of the Holley catalog. After adding these two areas together, then go back to the Holley catalog and pick out the equivalent Holley jet size and you're back to the same amount of fuel before removing the power valve. ------------------
Ted E.
Big inch Fords are plenty fast, but Y-Blocks's are fun when they run in the low 9.60's @ 135mph.
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