Holley Problems

Discussion in 'Other Automotive Tech & Talk' started by Mavaholic, Feb 26, 2018.

  1. Mavaholic

    Mavaholic Growing older but not up!

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    I have a 57 Wagon with a 400M & C6. The 400 does have a cam although the drive train was in the car when I bought it so I have no specs. Anyhow it had an Edlebrock carb. It ran good except was always rich. So I thought I'd try a Holly. So far that was a mistake, but hopefully I can figure this out with some help. As I said, the Edlebrock started fine but ran real rich especially when cold. Once warmed up it idled great and ran smooth. Put it in gear and no noticeable difference in the smoothness except the rpm dropped slightly. Installed the 600 Holley and things went to crap. The Holley is a remanufactured 600 CFM Electric Choke #80457S. I played with the idle adjustments and got just under 14" of vacuum, Idles about as smooth as the EB. But when I put it in gear, the rpm drops around 600 RPM and idles extremely rough. Cant figure out why the huge drop in RPM. Any ideas?
     
  2. Krazy Comet

    Krazy Comet Tom

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    Maybe someone will have a better answer, but I'm wondering why the idle didn't drop with the E'brock...

    I've seen where opening the secondaries slightly so less of the idle transfer slot in primary will be exposed is helpful... Assuming secondary is fully shut, adj stop so it's open approx .015-.020(use feeler gauge)... Yes you'll have to remove carb...
     
  3. Earl Branham

    Earl Branham Certified Old Fart

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    Hi Dennis, sounds to me like you have a vacuum leak in the carb somewhere. It sounds like the power valve is either broken (diaphragm), which creates a vacuum leak, or is too high a value. Tom has a good suggestion too, check the secondary to see if the transfer slot is properly set. Let me know what you find.
     
  4. Mavaholic

    Mavaholic Growing older but not up!

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    From what I've researched, the power valve has nothing to do with idle. Tomorrow I will pull the carb and check the secondaries and while the carb is off, see which power valve is in the carb. Its a new/remanufactured unit so I wouldn't expect the power valve to be blown but I may need to change it anyway to suit my setup.
     
  5. Crazy Larry

    Crazy Larry Member

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    If the power valve is blown, the engine will continue running when the air/fuel screws are turned all the way in.
     
  6. Krazy Comet

    Krazy Comet Tom

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    Agreed, plus if leak is severe enough the engine will be so rich it'll belch black smoke...
     
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  7. yellow75

    yellow75 MCCI Oregon State Rep Supporting Member

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    I would think that the carb has the new power valve check ball protection if not easy to install. Willing to bet it has a 6.5 pv in it
     
  8. Mavaholic

    Mavaholic Growing older but not up!

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    Got it idling nice at 850, in gear. Manifold pressure right around 10". Only problem is jumps up the 1550 in neutral. 700 rpm seems like a lot of drop. Never dropped that much with the EB. It does have a 6.5 power valve. Now adjustments on the rear throttle plates unless its up in the vacuum canister.
     
  9. groberts101

    groberts101 Member

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    10" at neutral idle or in gear idle? Either way.. even with a mild performance cam.. those vac readings are low as hell.

    Assuming the motor is semi-healthy.. if you have the distributors vac pot attached to the full manifold vacuum source(where it should be for best overall affect).. it's likely going in and out of assist mode(doesn't do a whole lot at 10" and typically falls completely away around 8") when shifting into gear. Also keep in mind that those big open chambered smog heads need tons of initial spark lead to get things popping well enough to jack up the manifold vacuum. This retarded spark delay causes a "lazy and confused vac pot" which creates a chain reaction that makes the booster and it's lo-speed/hi-speed metering system sluggish and then compounds the issues even further as combustion chamber pressures continue to fall. The vac gauge tells you if they have fallen via the number on the dial. How it works.. vacuum denotes burn efficiency.

    Here's a cheap and easy learning experience to see what a motor likes. Total timing at full rev's will go sky high so you can't really drive above 3,000 rpm with this quickndirty test but you can put it into gear and do light bunny hops to check out all the new torque and response that crappy factory distributor curve has been keeping from you.

    Mark your distributors current location and twist clockwise until it idles up a fair amount of rpm. Readjust the idle speed and reset idle mixture screws for steadiest manifold vac gauge reading each time you twist the distributor housing and gain more idle speed. Put it into gear and remeasure rpm and manifold vac drop.

    If the rpm/vac drop is still excessive going into gear then you likely have too much vac pot assist and not enough initial timing lead dialed in. Very common for factory systems to have far too much vac advance assist being added which detracts from the amount which should be used towards higher initial timing settings(which never fall away like the vac pot does under heavy throttle). Basically, you want a fatter and quicker (non-vac assisted) timing curve down low in the rpm range when you put the car into gear or stomp on it which will still fall short of detonation problems with the fuel/usage/weight(heavy wagon)/gearing/hotter weather, etc. From there you add about another 10° of manifold vac assist(the minimum most vac pots will adjust down to) to "supplement" the entire curve during high vacuum(same as saying "low load") when the motors not working as hard and becomes more heat and octane tolerant. This effect greatly contributes towards lean burns and helps mileage and overall efficiency. High vacuum motors idle much nicer too. NOX will burn your eyeballs but it'll run better then ever when you get it closer to right. lol

    You may know me by now and I'd likely say more but tight on time.. hope that helps.:)
     
    Last edited: Feb 28, 2018
  10. Mavaholic

    Mavaholic Growing older but not up!

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    I will check all this out tomorrow and get back. Thanks.
     
  11. groberts101

    groberts101 Member

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    Another word of caution.. more like a caveat in the tuning process. As ignition timing advances up to the engines combustion space tolerance(peak pressure allowance at low piston speeds/flow.. typically read as highest steady vacuum gauge reading).. as it relates to the existing fuel curves flow limits(relative to THAT specific combination of parts/fuel).. it increases the likelihood of detonation and certainty that leanout will eventually occur. lol.. sorry that was a mouthful all in the wrong order but hopefully it's legible enough to get the point.

    This lean condition can cause barely audible crackely rice crispies sounding misfires that can be heard through the induction. Careful putting your head over a carb to listen when screwing around with fuel or spark.. bad place to be if a fireball of raw fuel spits out. Leanout can sometimes be tough to see on the gauge at that point but as you keep advancing the ignition timing the gauge will get more unsteady and uncorrectable with further mixture screw adjustments. Beyond that you get into IFR tuning. The small erratic misfires will become more audible. Drive it even at low rpm/speeds and the carb will likely backfire and/or break up rpm and/or surge and/or rattle the motor to death with detonation. Never want to rattle any motor too hard but especially true of those with cast pistons. More easily eroded piston crowns and cracked ringlands are the brittle cast pistons big achilles.

    The quick-n-dirty test I mentioned above only teaches you the trends for what a motor wants to be given.. not bunny hoping around and spinning tires with the newfound torque and throttle response like a teenager. Very tough for me to fight those childish urges when I'm testing stuff out so I speak from long term experience there. LOL
     
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  12. Earl Branham

    Earl Branham Certified Old Fart

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    Does having a manual transmission have any effect on this?
     
  13. groberts101

    groberts101 Member

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    Color me confused. You mentioned it went down to xx" of vacuum in gear? Now meaning when you let out the clutch and crawl forward in 1st under no throttle?

    But to answer the question.. no it doesn't other than the timing advance allowance would be slightly more aggressive with more and lower gears due to increased torque ratio multiplication factors. More gear = less engine loading and quicker rpm rise. Which lends itself to slightly increased ignition lead, or at least more safety margin, over a slushbox.
     
  14. groberts101

    groberts101 Member

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    Pm me if you want to call while I'm working in the shop today and shortcut through all this forum learning/texting stuff.
     
  15. Mavaholic

    Mavaholic Growing older but not up!

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    Well I gave up on the Holley. After many suggestions and a few calls to the holley tech line nothing will fix this problem. It is definitely in the carburetor because I put the Edlebrock back on and its back to running smooth, idling at 850 rpm, and only dropping around 100 rpm when put in gear. So its not a timing or torque converter issue as I heard a lot. This Holley might be good on a manual car but it really sucks on an automatic. Still would like to know what the difference is.
     

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