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running poorly - F-head

Discussion in 'Early CJ5 and CJ6 Tech' started by 1968Jeep, Dec 31, 2006.

  1. Jan 13, 2007
    64kg

    64kg New Member

    Quincy, Ill
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    Oct 3, 2002
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    I had the same problem with my F head. Tried a rebuilt carter with no help. Tried a solex and it now runs great.
     
  2. Jan 14, 2007
    blevisay

    blevisay Oh Noooooooooooooooo! Staff Member Sponsor

    Portland Tn.
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    Wait........you have power brakes????????

    Bypass the vac for it (plug it).......I have had the diaphram leak before.........how the heck did you get power brakes?
     
  3. Jan 14, 2007
    1968Jeep

    1968Jeep Member

    St.Albert,...
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    Apr 12, 2003
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    That's the first thing I did - actually, that is where I have the vacuum gauge attached -makes test drives a little scary though..........no power assist....
    Overhead pedals and brake booster from a late 70's CJ-7, and master cylinder from a 4 wheel disc Firebird. Also a tilt column and seats from a 78 Camaro.....
     
  4. Jan 14, 2007
    blevisay

    blevisay Oh Noooooooooooooooo! Staff Member Sponsor

    Portland Tn.
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    (puts thinking cap back on)
     
  5. Jan 15, 2007
    Dabblin

    Dabblin Barn fresh 67 cj5

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    63
    Actually plugging the vacume line can cause problems. Help me out guys if I get this wrong. The pipe that the dip stick goes into has a 3/8" or so tube sticking out of it, a hose usually connects it to the aircleaner. At the very least it is just hanging down allowing air into, or out of, the crank case.
    The top of the valve cover has a knobby thingy (technical term from the manual) with a tube sticking out of it and it really needs to be connected to the PCV valve which is usually connected to a "T" fitting threaded into the cast iron intake manifold just below the carb mount boss. Failure to have this setup correctly can lead to over rich carburation, and excessive crank case pressure.
    You might try letting the vacume line leak and unplugging the breathers
    if they are blocked.
    As a test it won't hurt anthing, its a quick thing to do, and it may give you a direction to go after if it does work.
    Good luck
     
  6. Jan 16, 2007
    1968Jeep

    1968Jeep Member

    St.Albert,...
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    Apr 12, 2003
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    So, I was poking around a bit and found that the grommet for the brake booster vacuum line (on the booster) is split - gonna get another one today and see what's up.

    Wouldn't hooking up the pcv tube just be a vacuum leak anyways?
    Right now, the line from the PCV thingy (technical term) is just open to the atmosphere (I ran a rubber line up to the firewall area so it wouldn't suck in any mud)
     
  7. Jan 16, 2007
    Dabblin

    Dabblin Barn fresh 67 cj5

    Joined:
    Jan 2, 2005
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    63
    Its only a vacume leak if the system was designed without the extra air coming in from that point. I was having with a decelleration backfire and it was caused by my having closed off all the "Vacume Leaks" I could find.
    That was after I drained the oil/gas mix from the crankcase, (old carb had stuck open float, PO said it ran fine), discovered the goo on the bottom of the Dist and the bad ground to same. Then I tried plugging the various orifices (or is it orifi- plural of orifice?) leaking air into the engine as I endeavored to get her to start. That caused a puddle of oil due to the crankcase pressurizing and blowing oil out the rear main seal. All I can figure is that the Carb is sized and jetted so that the drop in intake vacume pressure caused by the PCV framus (Another FSM term I do believe) sucking air through the valve cover tube, allows the proper fuel/air mixture for Optimal combustion (optimal and Jeep?). The use of the intake vacume tap for the power brakes with a hole in the line may lean it out enough or too much. If you plugged the breathers you may be causing all sorts of difficulties as the pistons and rings are not designed to seal crank case pressure. The pressure could build in the top of the engine also and start pushing crankcase air past the intake valve seals, kinda what mine did, -- lost power-- died-- once it cooled down it would start again and then after a short while it started stumbling again.
    Just an Idea, if yours is showing its personality for a different reason
    maybe someone else can use the info.
    Best of luck:coffee:
     
  8. Jan 16, 2007
    sparky

    sparky done Staff Member Founder

    Toowoomba, QLD
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    The PCV hooks to a manifold vacuum source typically. If that manifold vacuum source is blocked off well enough then there shouldn't be a leak. The grommet could cause a leak though, maybe.
     
  9. Jan 16, 2007
    1968Jeep

    1968Jeep Member

    St.Albert,...
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    The fitting near the base of the carb (on the cylinder head/intake assembly) is plugged off on one side, and the other side is routed to the brake booster. The line from the pcv valve is open to the atmosphere and the air intake tube that attaches to the oil dipstick tube is in place, so there should be no pressurizing of the crankcase to deal with - it's kinda a road draft setup right now......
    I'm going to install the grommet and see how that turns out...
     
  10. Jan 16, 2007
    1960willyscj5

    1960willyscj5 Well-Known Member

    Mesa, Arizona
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    My F-Head doesn't have the two vacuum fittings below the carb, just one.
    :coffee:
    That line runs to the front, across the top of the cover below the waterpump, into a tee. One line from the tee goes to the crankcase ventilation fitting for the pcv setup. The other is capped. If uncapped, it would run to the bottom of the fuel pump/vacuum pump combination and then to the vacuum motors of the windshield wipers. I have electrics installed instead of vacuum, so don't have the extra lines from the tee and pump, plus have the newer fuel only pump.

    Thought occurs though. Could the vacuum demands of your brake booster be enough to upset the balance of things, carburetor wise? If you step on the brake when all this is occuring, does your idle smooth out? Or am I just confusing the issue more?:?
     
  11. Jan 17, 2007
    1968Jeep

    1968Jeep Member

    St.Albert,...
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    I never noticed a change when the brakes were applied.
    Is there any check valve or something in the pcv line from the manifold to the pcv fitting, or could I just put a vacuum line from the valve to the 'T' fitting near the base of the carb?
    I have the newer style fuel pump installed and have converted to electric wipers.
     
  12. Jan 18, 2007
    1960willyscj5

    1960willyscj5 Well-Known Member

    Mesa, Arizona
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    I'll have to look.
    It's a grand total of 40 degrees out there right now, which is really on the cool side for Phoenix. When it warms up a little I'll pop the hood. The jeep manuals ought to have something in them about the pcv system.:coffee:
     
  13. Jan 19, 2007
    1960willyscj5

    1960willyscj5 Well-Known Member

    Mesa, Arizona
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    :? I was just reading the thread on the gastank cap. Could you be having the same problem? Needing a vented cap or tank? sounds like the same problem, did you just change the cap or something? I don't think I would have considered that at all if I hadn't read that.:coffee:
     
  14. Jan 19, 2007
    1968Jeep

    1968Jeep Member

    St.Albert,...
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    I didn't change anything - but I did check how it ran with the gas cap off - no difference - the fuel tank is vented thru a line that goes to the air intake side of tha carb -
    I read that post too and figured I would check it and see...
     
  15. Jan 19, 2007
    1960willyscj5

    1960willyscj5 Well-Known Member

    Mesa, Arizona
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    The line on my F-head runs from the valve on the oil/fuel pump side of the block to the fitting on the head below the carb. :coffee:
     
  16. Jan 19, 2007
    1968Jeep

    1968Jeep Member

    St.Albert,...
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    Well, I guess the next step is to hook that up and see how it runs - hopefully I don't mess up the power brakes......
     
  17. Jan 19, 2007
    1960willyscj5

    1960willyscj5 Well-Known Member

    Mesa, Arizona
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    One of the things mentioned by Mr. Ludel is that the valves can effect it if they are not set to the correct clearance. Evidentley the less the clearance between the stems and the cam the worse the engine runs. Unless yours are hydraulics, which I don't think is possible with the 134.:coffee: :rofl:
     
  18. Jan 22, 2007
    1968Jeep

    1968Jeep Member

    St.Albert,...
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    Left the pcv alone for now, tried to drive it to work this morning - no power off the line, steady throttle seemed to be cutting in & out a bit, did not want to idle - had to play with the gas to keep it running. temperature gauge showed 195 degrees, but I was not getting any heat from the heater, and I smelled a bit of coolant - it will run if it is revved right up, but I don't trust it to get me anywhere.
     
  19. Jan 22, 2007
    1960willyscj5

    1960willyscj5 Well-Known Member

    Mesa, Arizona
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    Someone who is a better mechanic than I am will have to help you.
    The only other thing I can think of is someone has shoved a potato up the exhaust pipe, or put sugar in your gas tank. Some people are so nice to us!
    :coffee:
     
  20. Jan 23, 2007
    PeteL

    PeteL Member Sponsor 2019 Sponsor

    Hills of NH
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    Aug 3, 2003
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    Coolant smell, no heat? Need to burp the cooling system, possibly pull a hose off the heater and fill it with a funnel.

    I'm sure you've checked compression, but F-heads have a way of blowing head gaskets between the cylinders, with associated coolant loss, and exhaust gas in the radiator. Another sign is a "wet" sparkplug electrode in the bad cylinder, causing a skip each morning until it drys out and starts firing.

    Pete
     

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