Discussion in ''Da Nailhead' started by suntreemcanic, Nov 20, 2020.

  1. suntreemcanic

    suntreemcanic Well-Known Member

    Put together a 425 from parts of about 5 engines. It runs great and with a 3.08 rear end and a 5,000 pound car it spins one tire with just 1/2 throttle off the line. I am running Tom's pistons and Russ's camshaft. It has quite a vibration at 1200 RPM parked in neutral. I do not feel any vibration when driving. My vibration damper looks good, its from a 1959 401. The flex plate to the turbo 400 is assembled in the index hole on the crankshaft. Anyone have any experience like this? I would assume these engines should run real smooth.
  2. telriv

    telriv Well-Known Member

    Was the engine balanced when it was apart????
    Most common is the flexplate/flywheel is not indexed correctly.
    Could also be the used balancer.
  3. Stevem

    Stevem Well-Known Member

    That's a tad strange if the vibration gets fully canceled out once in gear and or driving!

    Are you sure you are just not have the motor run ruff out of gear and are calling that a vibration?

    If so I would confirm that at normal temp and out of gear that when you turn each of the Carbs idle mixture screws that turning them in will cause the motor to die, and turning them out will make the motor run ruff, but not die out.
  4. suntreemcanic

    suntreemcanic Well-Known Member

    No the engine was not balanced. I have done nothing to the new Edelbrock carburetor, I will try the adjustment. Can the transmission create the vibration? I am going to remove the balancer bolt and flat washer. The keyway and the timing mark should line up.
    Last edited: Nov 21, 2020
  5. suntreemcanic

    suntreemcanic Well-Known Member

    I pulled the balancer off today, the timing mark and the key way lined up perfectly. The rubber that appears to be squeezed out between the two parts was uniform all the way around. But I found a balancer on an old rusty 401. I cleaned it up and inspected it, it looked OK. I installed it and ran the engine, the vibration was still there. Tomorrow I am going to pull the transmission remove the torque converter and make sure the flex plate is indexed with the crankshaft. Then I am going to slide the transmission back on less the torque converter and start it. That will eliminate the transmission and torque convertor.
    Last edited: Nov 22, 2020
  6. Stevem

    Stevem Well-Known Member

    You should Be able to slide to the converter back enough on the input shaft to run the motor without unbolting the trans!
  7. Babeola

    Babeola Well-Known Member

    It could have been indexed wrong when balanced if they were not paying attention. You might want to try the flexplate in all positions while you have the trans out.

    Cheryl :)
  8. suntreemcanic

    suntreemcanic Well-Known Member

    Stevem, have you tried running the engine with the converter slide back? I have about 1/4 inch clearance. I considered that when I felt up in there with a bent end of a brass rod to check for proper indexing. That would save some work of reinstalling the transmission. I bought the converter about 10 years ago and it has been moved multiple times around the shop and I also rebuilt the transmission myself so I have a few thoughts about maybe one of those items is contributing to the vibration.

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