Compression Problems?

Discussion in 'Classic Mustang Specific Tech' started by mr.wwwiseman, Jul 30, 2013.


  1. mr.wwwiseman

    mr.wwwiseman New Member

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    I have a 1965 inline 6 260 engine that has been running a little rough. Spark plug 2 continually fouls. Plug 1 has 105-110 psi, 2 = 115-125 psi, 3 = 110 psi, 4 = 125 psi, 5= 115 psi, and 6 = 110 psi. I thought it might be that either oil was leaking around the piston rings or that one of the valves may be dirty and is not closing all the way but since #2 has higher compression than most doesn't that suggest against that? Car does not smoke or burn oil. Please help. Any solutions or tips on how high the compression should be are welcome. Thanks
  2. woodsnake

    woodsnake Active Member

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    Any oil in the water, or water in the oil?
  3. rbohm

    rbohm Founding Member

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    first that would be a 200. as for your compression readings, they are consistent, though perhaps a touch low. i would look to things like something in the ignition system or the fuel system requiring attention.
  4. mr.wwwiseman

    mr.wwwiseman New Member

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    No water in the oil. Just recently regapped the points, put in a new capacitor, new starter cellinoid, and new starter cable. Could it possibly be something like a slight clog in a fuel filter?
  5. woodsnake

    woodsnake Active Member

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    Any idea how old the timing gear set is? That will cause a lot of hard to identify running conditions..
  6. rbohm

    rbohm Founding Member

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    check the dwell reading, i forget the factory spec, but it might be out of whack and that will cause rough running issues.
  7. dennis112

    dennis112 Active Member

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    I've found some very weak valve spring on the 200ci motors that I have had throughout the years. Some have allowed the compression to drop to next to nothing. You could literally compress them with your hands. The springs are cheap to replace if you have an overhead tool and a few feet of 1/8" nylon rope. A big PLUS is that you could replace the valve stem seals at the same time which might help eliminate plug fouling.
  8. woodsnake

    woodsnake Active Member

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    Is the exhaust system original? Could have issues relating from a clogged muffler. That happened to me, when I had my 65 I6....The point here being no air out, no good air in...

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