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now I know why my car is weak.

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    now I know why my car is weak.

    I finally got around to doing a compression test on my motor. I checked 4 cylinders, 3 on one bank and 1 on the other. All four were between 95-100 psi. I tried the old trick of putting some oil in the cylinder to see if the compression came up. It didn't change at all. At least this confirms my long running suspicion, that I have valve problems. This directly relates to the low manifold vacuum, poor performance, and poor fuel economy. I was talking with my uncle about this, and he made a good point. The intake valve faces were cut, and the valve seats were all cut. New exhaust valves were installed. The problem is, the valve stems were not cut down any. The possibility here is that with stock rocker geometry, the valve stem is effectively slightly longer than it would be in stock form. I could actually be in a situation where the valves aren't completely closing. The other factor is the old valve springs. Probably if I put new springs on and actually bothered to check the lifter preload to verify my crackpot theory of the valves not shutting I could get a bit more out of it. Oh well, more motivation to install those other heads.
    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC grandpa spec white and cranberry

    1984 Lincoln Continental TurboDiesel - rolls coal

    Originally posted by phayzer5
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

    #2
    With hydrolics lifters the grinding should not effect it closing. Howeverm tired valves springs might, but I would think they would need to be pretty damn tired. How old is the cranks, rods, pistons? I hate to say it, but the fact that you drove filterless for a period of time would lead me to believe there are simply wear problems.
    Last edited by Blaze86Vic; 08-30-2006, 12:47 AM.

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      #3
      25k on the engine, and less than 5k was running filterless. Its not a wear problem. If it was wear on the walls or rings, I should have seen a noticeable jump in compression with oil in the cylinders. The valve springs have something like 150k on them, they're original from the engine. Rotating assembly and all is original, 150k. Original rods, crank, pistons. New bearings and rings were done with the motor. Cylinders were not bored, but they're fine. The factory crosshatch marks were visible when it came apart, no noticeable ring land, and the bore guage confirmed things as being fine. The cylinders all got a light hone job and thats about it. Crank has not been cut either, it was within specs tho the bearing clearances are just barely within spec. The bottom end is slightly loose, no doubt about it, but it holds respectable oil pressure. The other thing, if this was a wear situation I should have seen a change in manifold vacuum present. When I put this engine together, I started it with the vac guage hooked up. 16" of vacuum at idle with zero miles on the motor. I still get 15-16" vacuum depending on how warm the engine is and how high the idle is.
      Last edited by gadget73; 08-30-2006, 01:22 AM.
      86 Lincoln Town Car (Galactica).
      5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

      91 Lincoln Mark VII LSC grandpa spec white and cranberry

      1984 Lincoln Continental TurboDiesel - rolls coal

      Originally posted by phayzer5
      I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

      Comment


        #4
        Do a leak down test. Also do all 8 cylinders. Did you have the throttle opened all the way during the compression test?
        Last edited by turbo2256b; 08-30-2006, 05:59 AM.
        Scars are tatoos of the fearless

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