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Holley Carb problems

Discussion in 'The Hokey Ass Message Board' started by fifty7chev, Jul 27, 2013.

  1. junkyardjeff
    Joined: Jul 23, 2005
    Posts: 8,008

    junkyardjeff
    Member

    I have one of those carbs too and will check into the recall,if I known it had that type of floats I would not have bought it. I guess it would need new fuel bowls to convert it.
     
  2. 1971BB427
    Joined: Mar 6, 2010
    Posts: 6,969

    1971BB427
    Member
    from Oregon

    You may not consider that an adjustment, but every carb maker other than Holley does, and now with the new version Holley does also! For many years every repair kit for all makes of carbs describes the "adjustment procedure" for floats as bending the tab to set float level. This is the industry standard method for adjusting float levels, not a modification. This is not like bending springs on your suspension to adjust ride height, since that is NOT the way you adjust ride height normally. Bad comparison.
     
  3. fifty7chev
    Joined: Dec 22, 2008
    Posts: 26

    fifty7chev
    Member
    from Vermont

    Ok so I took the float bowl off of the carb and cleaned out the needle and seat. No issues there, and BB427, I understand what you mean by bending the tab on the float and was able to adjust it to a better position; however, when I put everything back together it started up great and ran for a few seconds but while trying to tune the idle circuit everything started flooding again so I tried turning the idle mixture set screws all the way in on both sides and test the power valve and turns out it was blown...got a new one and now waiting on time to install it. more to follow. Thanks all for the help.
     
  4. Deuces
    Joined: Nov 3, 2009
    Posts: 20,972

    Deuces
    Member
    from Michigan

    That'll make it run rich...:eek:
     
  5. fifty7chev
    Joined: Dec 22, 2008
    Posts: 26

    fifty7chev
    Member
    from Vermont

    Alright guys, I have a bit of an update. I replaced the power valve, however, I am now thinking that it was not actually blown. I hooked up the trusty vacuum gauge to the vacuum port on the carb to try and tune to max vacuum at idle and it turns out that I am only pulling about 6-8 inHg, does that sound possible for a 350/290 crate motor?

    edit: If this is an accurate measurement it would indicate that the power valve would not actually close at idle because it would have too low vacuum for the standard 6.5 power valve (if my logic is correct) which would be why I need my idle mixture screws turned all the way in (again, if my logic is correct)

    I know it has a "performance" cam in it and that can lower the vacuum from my understanding, but I was expecting to see more in the 12-15 inHg range. If this sounds like it could be an accurate measurement I am going to change to a 3.5 power valve and give it a try, my other thought was to buy a power valve plug to try and tune the idle circuit without the power valve being a factor to determine, as accurately as possible, the idle vacuum I'm pulling. Please advice because at this point I am getting a little frustrated...I am not a carburetor guru, but I have been trying to research and learn as much as I can and I am once again at the extent of my knowledge/experience. Thank you all for the most excellent help thus far!
     
    Last edited: Aug 5, 2013
  6. hoop98
    Joined: Jan 23, 2013
    Posts: 1,362

    hoop98
    Member
    from Texas

    Time to get the timing in order, if we are sure our ignition timing is right you need to check compression. The cam could be off.

    Wow lots of duration:

    This engine is not designed, nor intended to be used in any marine applications. Designed for pre-1976 street vehicles or any off-road vehicle. Engines installed in vehicles registered and normally operated outside of the United States carry no warranty. Camshaft lift is .450 intake / .460 exhaust. Camshaft duration at 050 is 222 degrees intake and exhaust. Lobe centerline is 114 degrees. Normal engine manifold vacuum for the 350/290 HP engine is 10-12 in. This engine cannot be used in vehicles with a GVW over 6,000 lbs.

    After you get it running better might want to look at a cam change.

    Hoop
     
  7. 1971BB427
    Joined: Mar 6, 2010
    Posts: 6,969

    1971BB427
    Member
    from Oregon

    I agree. That vacuum sounds way too low if everything is properly tuned. The power valve is doing it's job, and opening on low vacuum, but now need to figure out why it's so low. The specs for that cam and engine look much like what I'm running with my Isky 270, and mine has about 12" vacuum at idle. Only difference really is your cam is 114 LSA, which should give it even more vacuum than my Isky with 108 LSA.
    Time to tweak the timing with a vacuum gauge on the engine, so you can see if it varies with timing adjustment. Then if the vacuum goes up, and flooding stops, adjust the idle air mixture screws until you reach maximum vacuum also.
     
  8. mustang6147
    Joined: Feb 26, 2010
    Posts: 1,847

    mustang6147
    Member
    from Kent, Ohio

    Are you sure the valves are adjusted right? It seems they might be to tight. WoW that's low vacuum. You should be arounf 15 to 17. Is the needle bouncing a lot?
     
  9. fifty7chev
    Joined: Dec 22, 2008
    Posts: 26

    fifty7chev
    Member
    from Vermont

    I got a vacuum gauge and a timing light on the engine today and found that I was a little too advanced on my timing. my distributor clamp and not doing it's job very well (add to the shopping list), and when I adjusted the timing I got the vacuum to right around 12-13 inHg; however, it still kept running with the idle circuit completely shut off. I think it really is the fuel pressure that is keeping me from getting any further and it still smells like it's running crazy rich. So I think I'm ordering all the stuff tonight while I'm at work and will install it next week.
     
  10. Dan Timberlake
    Joined: Apr 28, 2010
    Posts: 1,327

    Dan Timberlake
    Member

    How did you determine the "better position?"
     
  11. toxic waste
    Joined: Dec 18, 2011
    Posts: 383

    toxic waste
    Member
    from Iowa

    Check your floats .Make sure they will float and that there not full of gas. You can buy a kit for the externally adjustment needles.
     

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  12. fifty7chev
    Joined: Dec 22, 2008
    Posts: 26

    fifty7chev
    Member
    from Vermont

    I made a calculated presumption that a flooded engine means too much fuel in the bowls. Based on that I looked at the maximum vertical position that the float could reach (well above parallel to float bowl floor) and decided it would be appropriate to try and lower the float maximum slightly within the bowl. I can't decide if it's truly better until I get proper fuel pressure going into the carb, but based on what I have been researching it was a logical step.
     
  13. toxic waste
    Joined: Dec 18, 2011
    Posts: 383

    toxic waste
    Member
    from Iowa

  14. fifty7chev
    Joined: Dec 22, 2008
    Posts: 26

    fifty7chev
    Member
    from Vermont

    there is no sight plug in the fuel bowl with the 4160 non adjustable float version. It is all guess and check with either a afr gauge or the trusty spark plug test.
     
  15. 1971BB427
    Joined: Mar 6, 2010
    Posts: 6,969

    1971BB427
    Member
    from Oregon

    Or pull the bowls off and do a quick visual. I use the blue gaskets on mine, so dropping a bowl quickly is easy, and they are reusable so saves money. A shot of Pam cooking spray also keeps them from sticking.
     
  16. n847
    Joined: Apr 22, 2010
    Posts: 2,707

    n847
    Member

    First off I just finished off a round of carb woes with my Plymouth, and it was a learining experience as I had no previous experience with them. My carb was made in 2010 and it needed a rebuild. Although I did determine I wasn't the first person to rebuild it! My power valve gasket was shot, needle was sticking, and it was missing the secondary metering plate (no I have no idea how it was even running).

    If you are adjusting the A/F mixing screws all the way in it should die, or atleast run very rough! It sounds like you have too much fuel pressure, and possibly a vacuum leak. Take a towl wad it up and put it down over the carb and see if the engine dies out. If it keeps running you likely have a pretty severe vacuum leak. I read the whole thread, but I never heard you say if you did the complete rebuild kit. Its really not that hard and you will understand everything alot beter after you do it. I do understand how frustrating this can be, but you will get it figured out. Pretty much every different thing people have said could be leading to your problem, so its a trial and error type of situation. My rebuild kit came from O'reilly auto parts for 30$ and they had it right there on the shelf. Feel free to shoot me a PM if I can be of any help. I'm by no means an expert, but I just went through the same problem!

    Good Luck...I promise you it will be a good feeling when you get it!
     
  17. fifty7chev
    Joined: Dec 22, 2008
    Posts: 26

    fifty7chev
    Member
    from Vermont

    n847, I am going with the fuel pressure correction first because I know I need to do that even if I do have to rebuild the carb later anyways. My direction right now is fuel pressure regulator setup, then determine the next COA...depends on how much better it runs with proper fuel pressure. Thanks for the kind words and I will message you if I get stuck.
     
  18. racer32
    Joined: Sep 22, 2007
    Posts: 745

    racer32
    Member

    DO NOT plug the power valve and try to "correct" for the missing power valve with richer jetting...it won't work. Your carb doesn't have any way to change "jets" in the secondaries, anyway. Vacuum is low enough that a 6.5 power valve isn't going to close. However, if nothing has been changed since it ran correctly (or a least a little better, it's probably got crud in it and is flooding because of a needle that's stuck. Got a GOOD fuel filter? Got a rusty gas tank?


    Here's a link for you: http://www.holley.com/data/TechService/Technical/power_valves.pdf
     
  19. fifty7chev
    Joined: Dec 22, 2008
    Posts: 26

    fifty7chev
    Member
    from Vermont

    I was not going to plug the power valve permanently; however, I was considering blocking it for a day to get the primary jets and idle circuit tuned properly (if anything I think the primaries need to be leaned out because I'm almost 1000 feet above sea level). Definitely going to tune the idle circuit first so I can get a good judge of idle vacuum before knowing if I have to change the power valve to a lower number. looks to me like with 10-12 inHg I would want to go with either a 4.5 or 5.5 power valve so I was going to try and determine which one would be correct. Of course, all this happens once I get the fuel pressure in check which requires me to wait until bills are paid and then spending the money. I have a good fuel filter on there, but it may be time to change that and I think I'm going to run the gas tank to "e" next time around and then drain remaining fuel to see how it looks. It shouldn't be bad because I have a new (as of 2008) aluminum fuel tank and all new lines at the same time, but with this new ethanol gas you never know.
     
  20. Standard gas&oil
    Joined: Dec 3, 2010
    Posts: 289

    Standard gas&oil
    Member
    from USA #1

    Do not plug the power valve, That's only used in full on drag racing. Just get the correct power valve after a vacuum reading.
     
  21. fifty7chev
    Joined: Dec 22, 2008
    Posts: 26

    fifty7chev
    Member
    from Vermont

    I have already said I am not going to run a blocked power valve. However, I need to make sure that the idle circuit is tuned properly before I can determine true idle vacuum to then determine the proper power valve to use so I was thinking it would be easiest to use a power valve plug to tune the idle circuit and then go on from there. thoughts on that?
     
  22. oj
    Joined: Jul 27, 2008
    Posts: 6,263

    oj
    Member

    Idle circuit don't have nothing to do with the power valve circuit.
     
  23. Rand Man
    Joined: Aug 23, 2004
    Posts: 3,969

    Rand Man
    Member

    I wonder how this turned out? I have a 750 that is flooding like crazy. There are some good, basic tips here.
     
  24. Dapostman
    Joined: Apr 24, 2011
    Posts: 294

    Dapostman
    Member

    I had a problem with a Holly rebuild that I got through NAPA, It worked fine for the first few days then kept getting richer and richer, the problem was the material used for the accelerator pump, it was NOT ethanol compatible and the fuel was leaking through. Who the hell makes anything for today’s fuel that is not ethanol compatible? I had to rebuild a factory rebuilt carb.
     

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