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Life expectancy for a Holley power valve

Discussion in 'The Hokey Ass Message Board' started by junkyardjeff, Aug 30, 2013.

  1. junkyardjeff
    Joined: Jul 23, 2005
    Posts: 7,255


    I noticed the 55 has a slightly rougher idle and smells a little rich so I am thinking its probably time for another power valve,can not remember any backfires and I have almost 3 years on this one and that is about how long I got from the others so is this the norm. I presume the crappy gas is the problem if there was no backfires and I used Holley power valves so does anyone know if there are better ones made or to be safe just replace it every other year.
  2. first time you nail it......sorry....Carter guy here....
  3. hillbilly jim
    Joined: Nov 14, 2010
    Posts: 34

    hillbilly jim

    Try and buy some av gas at the airport and run it and see if helps,Best thing in the world for the holly's
  4. F-6Garagerat
    Joined: Apr 12, 2008
    Posts: 2,651


    1.2 seconds before your first backfire.
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  5. classic gary
    Joined: Sep 24, 2009
    Posts: 497

    classic gary

    You might check the floats, they don't like today's gas and sink sometimes.
  6. damn for those days we/I worked at the airport....draning and pumpin' some of that 100plus avgas into my runner's....
  7. slammed
    Joined: Jun 10, 2004
    Posts: 8,161


    Pull the needle/seat and look (magnifying glass) at the O-rings condition. Should be full not even with the body. Mine was going away and acted like what you are describing. Stop any ethanol use.
  8. junkyardjeff
    Joined: Jul 23, 2005
    Posts: 7,255


    Still has the original needle valves so I will check them,carb has about 25,000 miles so probably about time for a kit.
  9. indyjps
    Joined: Feb 21, 2007
    Posts: 3,595


    Take the time to install the kit to prevent a backfire blowng the power valve, I don't remember what its called, been a while since I've done one. found it.
  10. stimpy
    Joined: Apr 16, 2006
    Posts: 3,547


    no backfire ball , the first time it sneezes, with one man been a few years since I rebuilt them on my freinds car and runs every summer when the weather is nice and uses EPA E-10 ... most of them die from backfiring or overtorquing them down ( distorts and rips the diagphram ) . I would check the needle,seats and float level .
  11. chopolds
    Joined: Oct 22, 2001
    Posts: 5,675

    from howell, nj
    1. Kustom Painters

    If it is only 5 years old or so, it probably had the backfire protection valve in it already.
  12. indyjps
    Joined: Feb 21, 2007
    Posts: 3,595


    Chopolds, you are correct.
    JunkyardJeff, you could check with companies providing e85 holley conversions to see if they will sell just power valves if you think the E10 is eating them.
  13. junkyardjeff
    Joined: Jul 23, 2005
    Posts: 7,255


    The carb is about 8 years old and I hope it has the backfire protection valve.
  14. Nitrobaron
    Joined: Feb 3, 2007
    Posts: 65


    I had a similar problem. Mine too was deteriation of the "O" rings on the needle and seat. The lower "O" ring was almost gone and allowed fuel to seep past avoiding the needle and seat.

    I replaced with a new needle and seat assembly, re-set the float level and all is good. Didn't even have to pull the carb off the car.

    It may be possible to just replace the "O" rings, but I could not find the right size, plus the carb was about 20 years old, so I figured it was time for needle and seats anyhow.

    Pull the sight plugs (one at a time) and carefully check the float level. If fuel spills out and you formerly had the float set right, my bet is on the needle and seat.
  15. aaggie
    Joined: Nov 21, 2009
    Posts: 2,529


    I bought tuning books and researched Holly problems getting my last SBC 400 running and I don't think the power valve is involved with idling problems. It's function is to aerate the fuel from main jets in the transition off idle. It does sound like a float level problem or sticking floats.
  16. Engine man
    Joined: Jan 30, 2011
    Posts: 3,476

    Engine man
    from Wisconsin

    We had lots of power valve problems on dirt circle track racers. The engine is revved way up then backed off going into the corner making maximum vacuum and it seemed to suck the diaphragm right out of the power valve. Most would fail after a couple of races. Vacuum holds the power valve closed so when the diaphragm fails, the power valve is open all of the time and it will dump gas at idle. The carb shop that sponsored us found some heavier duty power valves.
  17. burnout2614
    Joined: Sep 21, 2009
    Posts: 612


    Some good ideas above. I would replace it with a 4.5 personally. Even though your vacuum may dictate a 6.5 I have had better luck dropping down. Depends on how radical your cam is. peace
  18. Try a little sea foam for all it's worth. Seriously.
  19. junkyardjeff
    Joined: Jul 23, 2005
    Posts: 7,255


    As soon as I get the radiator repaired I will get back on the carb issue,last weekend it started leaking so I put some stop leak in it to get me home and was hoping it would last me the rest of the season but fond a very large puddle in the garage today so out it came. Recent recore and third time leaking from the same spot which is a seam where the tank is soldered,do I take it back to the guy who fixed it twice or find a new shop.
  20. mustang6147
    Joined: Feb 26, 2010
    Posts: 1,847

    from Kent, Ohio

    I always plug the PV.... But hey, 3 years and now a rebuild? I would take that. Especially with todays gas.....

    Freshin it up and roll another 3...

    1/2 the fun with old cars is workin on it right?

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