C2: Bad Motor Mounts? Long post... - NCRS Discussion Boards

C2: Bad Motor Mounts? Long post...

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  • Dan Pepper

    C2: Bad Motor Mounts? Long post...

    How much does an engine "flop around" if motor mounts are fatigued?

    Over the past few months I've been experiencing problems with the clearance between my hood and ignition shielding. The car is a '66 L36 AC coupe.

    The wing nuts fastening the shielding lid have started to rub the underside of the hood. They even exert enough pressure on the lid that it squashes the coil wire causing it to short out - and kill the engine instantaneously while driving. I recently installed a new clutch, and had the distributor rebuilt. I figured I may have put her back together wrong causing the clearance problem, but I don't see how that could happen as the car runs and drives fine.

    Also, just yesterday, I noticed that the alternator fan rubbed on the fiberglass hood brace and taken about 1/4" of material off of it. This, I'm sure, is a new development as I haven't seen that wearmark before.

    I crawled under the car and looked at the original motor mounts: one appears to have a crack in the rubber. I've ordered new mounts (exact repros?) from LIC, and hope this will fix the problem. Under normal driving conditions, would an engine jump around that much (and lift vertically) to cause this kind of interference with the hood? She's parked until I find the problem.
  • Stephen L.
    Extremely Frequent Poster
    • May 31, 1984
    • 3148

    #2
    Re: C2: Bad Motor Mounts? Long post...

    The engine will not flop like a whale if the mounts are good. Sounds like your's are severed.... at least on one side if not both. Don't forget to replace the one at the tranny too.....

    Comment

    • Mike McKown

      #3
      Re: C2: Bad Motor Mounts? Long post...

      It won't really flop around if the mounts are bad (unless both of them are broken). It usually raises up off the severed frame portion when the engine torques on acceleration. Never had my head down there when a mount failed but I would guess the left side of the engine could/would raise two inches on a fairly rapid start on the left side.

      If your mounts are bad, you should be able to hear/feel an audible thump on take off when the engine rises and then falls back on the frame mount.

      Comment

      • Michael W.
        Expired
        • April 1, 1997
        • 4290

        #4
        Re: C2: Bad Motor Mounts? Long post...

        Usually the fan hits the shroud also, have you checked there?

        Comment

        • Dan Pepper

          #5
          Re: C2: Bad Motor Mounts? Long post...

          Nope - fan has not hit the shroud - and haven't heard any noises. Although it is hard not to "use the torque" that the 427 provides from dead stop I'll replace the mounts - and inspect the original ones once they are out. Hopefully, the problem will be solved.

          Comment

          • Larry S.
            Very Frequent User
            • August 31, 2000
            • 356

            #6
            Re: C2: Bad Motor Mounts? Long post...

            How is the door gaps on the car by the front fenders?are the open on the top and close on the bottom

            Is there anyway the front glass is sagging or drooping?I would think if you had a bad motor mount for sure you would know it after racing the motor.

            Comment

            • David W.
              Very Frequent User
              • December 1, 1999
              • 272

              #7
              Re: C2: Bad Motor Mounts? Long post...

              It's usually the left one that goes bad first as that is the one that receives the most torque on acceleration. A very good sign is if the engine increases speed as you take off as the engine movement will force the accelerator linkage to pull the carb linkage backward. Another sure sign is accelerating while turning left which will even further exaggerate the situation. Be careful with that much horsepower as even on my small block it wanted to get away from me.

              Comment

              • Dan Pepper

                #8
                Re: C2: Bad Motor Mounts? Long post...

                The door fit and windshield glass is perfect. But I have noticed a surge in acceleration on brisk take-offs - thought it was just a carb adjustment thing. Sounds like maybe a symptom of bad mounts though. The new mounts should be here early next week - will have them installed that evening. Will post a report.

                Comment

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