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Technical 1959 Oldsmobile 88 with factory 371 4 bbl and 3 speed manual trans vibration

Discussion in 'The Hokey Ass Message Board' started by senginc, Mar 1, 2021.

  1. senginc
    Joined: Jul 18, 2009
    Posts: 312

    senginc
    Member
    from B'ham, AL

    This is a very low mileage car that the clutch was slipping but with the trans in neutral the engine was very smooth.

    I decided to have the 11" clutch disc and 3 finger pressure plate rebuilt locally since I could not find any new clutch kits. The clutch disc rivets had left small grooves in the pressure plate and the flywheel. They machined the pressure plate and flywheel surface.
    I paid them to balance the pressure plate also.
    I had marked the flywheel and crank and installed the flywheel with 75 ft lbs alternating. I installed the clutch assembly and alternated tightening the pressure plate bolts.
    Finished up and took it for a test drive, the clutch engagement works fine, a little shudder at first but I feel that will smooth out with time.

    Now in neutral the engine vibrates pretty bad ~ 2000-2500 RPM is the worst (haven't put a tach on it yet) but continues to vibrate on up to 3500-4000 RPM. The vibration feels kinda like 2 plug wires are off ,they are not :)

    I think the flywheel was for an external balance engine. I wonder if machining a a counterbalanced flywheel can affect the external balance engine smoothness.

    I guess I should try stacking washers on pressure plate bolts to see if I can affect the balance.

    Any suggestions. Left Front 119904126_3114621411982506_4154889278770349049_n.jpg
     
  2. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 6,250

    Ebbsspeed
    ALLIANCE MEMBER

    THAT is a BEAUTIFUL automobile! Did they balance the flywheel for internal balance? AFAIK the 371 was an external balance engine.
     
  3. senginc
    Joined: Jul 18, 2009
    Posts: 312

    senginc
    Member
    from B'ham, AL

    I don't know for sure. If they did it is permanently screwed up. Finding another good 371 flywheel is not likely.
     
  4. senginc
    Joined: Jul 18, 2009
    Posts: 312

    senginc
    Member
    from B'ham, AL

    In 1991 I installed a rebuilt clutch assembly (on a new 350 from the Chevy dealer) by the same rebuilder and it vibrated. Installed a new Borg and Beck kit and it was much better.
    That Chevy 350 was made in Mexico at the time and was never balanced right though. I had a shop use a strobe with engine in car and stacked washers on the flywheel and balancer and made some improvement.
     

  5. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 6,250

    Ebbsspeed
    ALLIANCE MEMBER

    @GOATROPER02 might weigh in and give you some ideas. Refacing the flywheel shouldn't affect the engine balance, as the additional material for the external balance is on the engine side of the flywheel, not the clutch side. Surely the machinist would know better than to cut on the backside of the flywheel.
     
  6. 47streetrodder
    Joined: Oct 27, 2007
    Posts: 104

    47streetrodder
    Member

    I don't understand why it's only vibrating in neutral. Was the vibration noticed right after the clutch rebuild or did it start sometime after?
     
  7. senginc
    Joined: Jul 18, 2009
    Posts: 312

    senginc
    Member
    from B'ham, AL

    It vibrates in all gears. I mentioned in neutral to isolate from the transmission back.
    Driving the car vibrates until the clutch is pushed in and the engine goes back to idle.
    The vibration started as soon as the engine was started after the clutch rebuild.
     
  8. BJR
    Joined: Mar 11, 2005
    Posts: 9,814

    BJR
    Member

    Obviously the flywheel, pressure plate, clutch disc is out of balance. I would take the pressure plate and flywheel back to whoever re surfaced it and have them balance it as a unit, and mark it for re assembly. I would bet that fixes it.
     
  9. Agree, it seems since the problem started with the changes you made, go back and have the balance checked.
     
  10. rockable
    Joined: Dec 21, 2009
    Posts: 4,429

    rockable
    ALLIANCE MEMBER

    Did you replace the pilot bearing? I screwed up and put the wrong pilot bearing in my Plymouth and ended up with a vibration. Had to pull it all apart and change the bearing. Thankfully, everything smoothed out after that.
     
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  11. Eddie
    Joined: Apr 2, 2006
    Posts: 562

    Eddie
    Member
    from Georgia

    Only the clutch assy. can be balanced independently, not the flywheel as it is balanced as part of the engine. If the machine shop balanced the flywheel, that is the problem. If they did, you're screwed. And, if they did, is there not a manual flywheel left from the Cannon estate? Personally, I would try to run the engine without the clutch assembly installed to determine which is the problem. Also, could there be a problem with the harmonic balancer?
    Eddie
     
  12. senginc
    Joined: Jul 18, 2009
    Posts: 312

    senginc
    Member
    from B'ham, AL

    I removed the pressure plate and disc today and ran the engine. Much to my displeasure the vibration is the same with the flywheel only. On the good side maybe the pressure plate and disc are balanced.
    I removed the flywheel and inspected the backside and it is still slightly greasy/ dirty so they did not alter the counterbalance on the rear.
    I am going to put a dial indicator on the flywheel mounted to the crank (it will only go on one way) to see if there is any runout near the edge and then check at maybe 2 places closer to the center to see if there are any waves.
    Unfortunately I have never seen any Oldsmobile flywheels in Malcolm Canon's stuff.
    I don't think the harmonic balancer would have failed during a clutch job, the engine was smooth as glass before I started the clutch job.
     
  13. senginc
    Joined: Jul 18, 2009
    Posts: 312

    senginc
    Member
    from B'ham, AL

    The 371 is externally balanced.
     
  14. Eddie
    Joined: Apr 2, 2006
    Posts: 562

    Eddie
    Member
    from Georgia

    That's good news that they did not balance the flywheel. I wish that you had checked runout prior to removing the flywheel but too late now. Be sure to check closely the crank flange and flywheel mounting surface to crank for any burrs, etc. prior to install, run again without clutch. Be absolutely positive that flywheel can only be mounted one way.
    Eddie
     
  15. Eddie
    Joined: Apr 2, 2006
    Posts: 562

    Eddie
    Member
    from Georgia

    One more thing, I know that you checked the plug wires but is it possible you let the dist. cap hit the firewall and it cracked?
     
    Paul likes this.
  16. senginc
    Joined: Jul 18, 2009
    Posts: 312

    senginc
    Member
    from B'ham, AL

    I thought about that last night - I will check today.
     
  17. I had a similar problem on my 4 speed toploader equipped hipo 289 '65 Falcon. Had the trans, clutch, pressure plate, pilot bearing in and out a dozen times chasing the vibration...convinced the shop that re-built and balanced the clutch and pressure plate screwed up...I finally ran the engine without the clutch/pressure plate/trans...and it still vibrated.

    I had installed an alternator with a new "hipo only" pulley (larger diameter with deeper belt grooves) that I had acquired from our favourite auction site while the clutch was being repaired. The hole in the center of the pulley was offset enough that the pulley had a cam like affect...and with the fanbelt tight it caused a vibration. I sheepishly apologised to the clutch rebuild shop for having ripped a strip off them. All that to say, if you've done any other work to the car, you might look there as well. Good luck.
     
    Last edited: Mar 3, 2021
  18. senginc
    Joined: Jul 18, 2009
    Posts: 312

    senginc
    Member
    from B'ham, AL

    Unfortunately for me, I have not changed any thing but the clutch since I got the car last September.
    However, I do have a water pump that has a sloppy bearing - but again other than the water pump noise at idle speeds and the slipping clutch the car has been trouble free. I will remove the belt and see if the vibration is better.
    I put my timing light pickup on every spark plug wire and it flashes so I probably don't have a cracked distributor, etc.
     
  19. senginc
    Joined: Jul 18, 2009
    Posts: 312

    senginc
    Member
    from B'ham, AL

    Used a Vibration App (Vibrometer) on my Android Smartphone (uses the phones accelerometer) and connected my timing light to get RPM. Vibration came in strong from 1800-2500 RPM and also higher RPM harmonics not quite as strong..
    Removed belt - no difference..Verified with my timing light that all spark plugs wires were firing.
    I decided to try a bolt for weight on the flywheel without the clutch assembly. I picked a 5/16"x 3/4" long (weight 10 grams) and put it in one of the flywheel holes.

    ************** MAGIC ON THE FIRST TRY ************* It smoothed the vibration from 1800-2500 RPM and also higher RPM harmonics to acceptable levels. :)
    I am going to drill and tap the edge of the pressure plate and screw the bolt in to try the assembly and if good weld in place.
     
    Last edited: Mar 3, 2021
    loudbang likes this.
  20. Eddie
    Joined: Apr 2, 2006
    Posts: 562

    Eddie
    Member
    from Georgia

    Do you know the history of this car/engine. With all you have been through and now corrected the problem, is it possible that the complete (including clutch and plate) rotating assembly was previously balanced and final balancing was achieved at the pressure plate? Therefore when machine shop neutral balanced the PP, threw off the balance of the total assembly. Nothing else makes sense to me.One more thing, be sure when bolting back together, align the added weight with the same hole that you used in the flywheel.
    Eddie
     
    Poverty cap likes this.
  21. 37slantback
    Joined: May 31, 2010
    Posts: 480

    37slantback
    ALLIANCE MEMBER

    I was curious about the speedgem ( Bendtzen) olds 371/394 adapter kit that comes with flywheel. So, is the flywheel and clutch assembly balanced and just bolt-on in place of old flywheel and clutch asembly?
     
  22. senginc
    Joined: Jul 18, 2009
    Posts: 312

    senginc
    Member
    from B'ham, AL

    I have a friend who used the automatic conversion kit from Bentsen on Olds and Buick engines and it works perfect, easy install.
     

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