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2f compression numbers

Discussion in '40- & 55-Series Tech' started by Ullr, Mar 7, 2004.

  1. Ullr

    Ullr

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    I tested all the cylinders dry, then with a little oil in each one. These are numbers:

    Before oil: 120, 120, 122, 125, 125, 135

    After oil: 126 130, 126, 131, 131, 145

    So my rings/cylinders are leaking some, but do you think its very bad? What is good compression on a 2f?
     
  2. Ullr

    Ullr

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    Another question: My plugs are fouled with a black, wet looking gunk, so it looks like im burning oil. Could this oil be coming up through the leaking rings/cylinders, or is it more likely the head?

    Any input is greatly appreciated, Im trying to decide if its worth rebuilding the head or just start looking around for another 2f engine.
     
  3. 60wag

    60wag SILVER Star

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    I think a fresh head (flattened and valve job) combined with a sealed manifold and a rebuilt carb would get your rig running great. Does it smoke noticeably if you're engine braking coming down a long hill? If it does then the valve guide seals are probalby shot.
     
  4. Ullr

    Ullr

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    Funny you mentioned the manifold. My exhaust and intake manifolds are missing bolts it turns out, and make an audible noise when the engine is running. If i place my hand near the missing bolts area I feel hot air/ gasses. I also see soem oil seepage from the base of each sparkplug, confirming the fact I have oil in my cylinders.

    Im glad you think I should work on the head, carb and manifolds. I would rather work on this engine and get it running well and and learn than just put a new/used engine in. Ill start ordering parts.

    Ill buy the beer if you want to swing by my place in Boulder when I put the head back on!
     
  5. Ullr

    Ullr

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    Oh, it runs best downhill, havent noticed any smoke but I will go check it out tommorow.

    The issue I have really is rough running and lack of power uphill or when accelerating.
     
  6. fjcruiser

    fjcruiser

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    The compression numbers seem pretty good.
    Have you given it a tune up? I would go through everything (plugs, wires, valves, vacuum leaks, carb rebuild, etc.)
     
  7. IDave

    IDave

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    Well, you need to fix/tighten those manifold nuts. You have a vacuum leak as you describe it, and that is screwing you up!
     
  8. Kief

    Kief

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    I don't think that your rings are the problem, your compression didn't jump that much when you added oil, I have an f motor that has 100lbs on a jug or two and it doesn't fowl plugs, I would say it is the head/ valve guide seals, if that is the original motor then the seals are probably all dried out and cracked. Get the head redone. When you pull the head see if there isn't much of a ring ridge( I have never seen much of any), maybe put in some new rings. Before you do any of this check the oil pressure. If it idles at 25-30 and at rpm is 50 to 60 then you should be in good shape. If you have crummy oil pressure then go through the motor. Don't trust my spec's ... double check them in the manual as I am too lazy tonight. Good luck!