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Chevy 6 harmonic balancer wobble. Am I SCREWED??

Discussion in 'The Hokey Ass Message Board' started by Tugmaster, Nov 14, 2009.

  1. I got the 250 that I put into my 50 Sedan from a buddy of mine this summer. I had it on the engine stand for repainting and I pulled the balancer to paint the block. On the 250 six the crank is not drilled and tapped to allow a install tool like on a smallblock. So when it was time to install it I put the balancer in the oven a 180 for about an hour and I shot the snout of the crankshaft with loctite freeze-it. It's used for breaking fro frozen bolts. It supposedly will cool shit to -45. Anyway I slid it on about a third of the way and used a wood block and a giant rawhide mallet to get it the rest of the way up.
    Jump forward to today. I'm getting ready to fire my motor for the first time so I want to make sure I got oil pressure. I pull the plugs and roll the motor over till I got pressure on the guage. Well, I look at my balancer and it is friggin wobbly as hell. I don't think I could have bent the crankshaft when I installed it. WTF?? Any suggestions. The motor was pulled from a running car and does not have a ton of miles on it. Thanks, Todd
  2. man that sucks if it's broken. I don't know about the six cylinder. But the 355sbc in my blazer has a noticeable wobble from the balancer while running. but nothing I am worried about. It's got 15k on it now.
  3. If you bent the crank you are a big big dude.

    Look at it real close and make sure it is all the way on and not part way on and crooked.

    Sounds like you probably need a new balancer.
    Budget36 likes this.
  4. squirrel
    Joined: Sep 23, 2004
    Posts: 49,264


    the damper on the 250 in my kid's car had the outer ring get loose recently, I bought a new damper for it and put it on, problem solved. They make high quality replacements in china now, you know

    Should not need to heat/cool stuff to put that damper on, just use a block of wood and a bfh.

  5. It is on all the way. It is flush with the crank snout which is how it was before I took it off. Also, the belt seems to line up with the water pump pulley. I'm wondering if I "tweeked" the elastic shit that is sanwhiched between the 2 pieces.Todd
  6. Mr48chev
    Joined: Dec 28, 2007
    Posts: 29,546


    I'd say that you pretty well cooked the rubber ring between the hub and outer ring and it isn't wanting to hold the outer ring anymore.

    I've seen guys knock the rings loose (the results of) with a bfh while they were trying to knock the damper off the engine by hitting the ring from the back side.
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    COCONUTS likes this.
  7. dave lewis
    Joined: Dec 12, 2006
    Posts: 1,372

    dave lewis

    Todd, find a new balancer...
    Then , before you do anything else....drill the dang crank !
    It already has a nice pilot/taper to center the drill. Get a mr gasket # 945 ( bolt and thick washer ) Drill the crank for tapping 7/16-20 threads.
    Then you can use the install tool..., use a drop of locktite on the bolt....and not worry about it walking off the crank when you are doing burnouts in front of the house !! LOL..
  8. Dave,

    How hard is it to drill the crank? I figured it be hardened steel and be a bitch to drill. I will have room to do it with the engine in the car. There is something un-natrual to about beating it on with a hammer and I would rather do it the easy/smart way and not have to deal with this again. Todd
  9. dave lewis
    Joined: Dec 12, 2006
    Posts: 1,372

    dave lewis

    Todd, they drill like butter ! The 250 has a cast crank and you will not believe how great it will drill.. BTW the steel crank drills almost as easy..
    Just to make it easy on yourself, buy a new tap and the correct drill. Do not go cheap here ! Quality drills and taps save lots of trouble.
    I even drill and tap 216/235 cranks.. I consider it cheap insurance..
  10. Thanks Dave. I have a Drill Doctor and ALWAYS sharpen my bits before I use them. That thing was money spent. I'll just take it real slow and make sure I drill it straight. Lots of Rapid-Tap too!!!Todd
  11. Dave,

    When you did this was the motor in the car? How did you keep the bit perfectly straight when drilling the crank? I wouldn't want to drill the hole crooked. Thanks, Todd
  12. Any chance the pulley itself is bent and not the dampener?


    I don't think 180* F will hurt the rubber ring.

    It's common for underhood temps to exceed 250* F and modern cars will approach 300* F.
  13. Truckedup
    Joined: Jul 25, 2006
    Posts: 4,130


    Dampers have been hammered on for years.Old service manuals show the factory tool and the big hammer.The object is to beat on center of the hub only and a piece of thick aluminum works well,don't directly strike the hub with the hammer.Placing the damper in boiling water for 15 minutes before driving it on really does help.Just remove it quickly from the water and drive it on.Drilling and tapping the crank snout is better of course so you can use a installer tool.
    Next post will be "I broke off the damper installer tool ,how can I remove the piece from the crank snout?" :D
  14. I just finished pulling the grille and radiator. You can actually see where the outer hub of the balancer is tweeked in relation to the inner hub. My screwup no doubt!
    I still have not decieded weather ti drill and tap the crank snout or drive on the new one. If I do drive it on I will definetly come up with some sort of fixture to drive it on with. Oversize socket or something. Todd
  15. I don't like driving them on unless you can back-up the crank. Otherwise the one thrust surface you have is taking all that beating and it is a soft material that is designed for imbedability and lubricity, not pounding. Drilling the crank is the right thing to do. Make sure there are no burrs on either the crank or the new balancer, polish with emery, use some type of lubricant. The original design being a press fit called for it being tight, but with a bolt this is not so critical so a bit of polish goes a long way toward an easier install.
  16. RAY With
    Joined: Mar 15, 2009
    Posts: 3,133

    RAY With

    You also have the option of sending the damper to --Damper Doc-- in Cal and there way accurate and better than the chineese crap.
  17. dave lewis
    Joined: Dec 12, 2006
    Posts: 1,372

    dave lewis

    Todd, the pilot in the crank is already centered.
    Be brave !
    If you can have somebody spot you while you drill, great !(to look @ the other plane that you cant see ) The person drilling usually can only see the side plane and the spotter will look at the up and down..
    The other option is to level the motor and use one of the Fancy new drills with a bullseye level built in!
    Really though, you might be worrying too much...I have done it many times without help...No problem.
  18. desoto44
    Joined: Oct 3, 2009
    Posts: 7


    I have a problem with a 1939 chevy 216 harmonic balancer. The engine has a little knock in the front end. I found that the harmonic balancer key knocks back and forth in the keyway. so the harmonic balancer is loose on the crank.
    Seeing your posts. I wonder if I could just drill the crank and install a bolt and washer to hold the harmonic balancer solidly onto the crank and eliminate the slop that way.:eek:
  19. pdq67
    Joined: Feb 12, 2007
    Posts: 787


    I bought a 7/16" X 5" long fine thread Grade-8 bolt and threaded it all the way to the head so I can use it as a SBC damper pusher.

    Did the same thing with a 1/2" bolt for my BBC. They are in my tool box next to several other homemade "tools"..

  20. JohnEvans
    Joined: Apr 13, 2008
    Posts: 4,883

    from Phoenix AZ

    Where is the slop? Damper or crank? First off use a new key . drilling and tapping the crank would be a good start. If the crank key slot is loose use some JB Weld around the key when you install the damper. Bad damper key way replace the damper if at all possible.
  21. desoto44
    Joined: Oct 3, 2009
    Posts: 7


    Thanks John Evans and all y'all. The slop is due to the crank being 70 years old. the crank snout shows evidence of a pipe wrench jaws. Last rebuild I suppose the mechanic tried to backyard Knurl it so the harmonic balancer would fit a little tighter.

    But she is a loose fit. I may try to get an oversize keyway made to eliminate some of the slop between the crank and the balancer, but I'm pretty sure at this point I am going to:
    Have the hand crank jaws on the balancer ground or machined down flat, so it will accept a bolt and washer. Drill and tap the crank snout, then install the balancer with some JB weld. Tighten her up and see if she can hold all the torque that 85 h.p. can produce without slipping again.
    Real backyard engineering. Wish me luck.
  22. plow
    Joined: Jun 28, 2013
    Posts: 72

    from Louisana

    I tried to repair a stripped bolt today. I'm not sure if I drilled it crooked or the guy before me drilled it crooked. none the less, It's crooked. it's tapped and a bolt goes in ok. My plan is to bake the balancer in the oven at 190*, Chill my snout with air duster turned upside down, then beat the balancer on.

    What has me worried is the bolt. assuming the balancer is good to go, would the crooked bolt cause a wobble?

    In this case, Maybe using a lock nut might correct the off center angle of the bolt.

    I REALLY do not want to pull the crank and have it machined an all the other stuff that goes with it $$$$$$$

    What do y'all think?
  23. models916
    Joined: Apr 19, 2012
    Posts: 380


    Is it the outer ring or the center hub that is moving? GM manual says to install the dampener with a Big hammer.
  24. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,912

    dirty old man

    For the original poster with the 250cid six, unless you plan to twist on that engine, using all it can spin, I'd just get a new or rebuilt damper, heat it in boiling water and install using the BFH and a block of oak wood, or better yet, the aluminum block suggested by Trucked Up. The early sbc engines depended on a press fit and unless you twisted hell outta them, all was OK. But if you're gonna twist hell outta it, then a retainer bolt should be used.
    As a machinist of almost 50 years experience, I don't much trust "eyeball" alignment, especially with the engine in the frame. If I were confronted with this situation, I would make a drill guide. If you know a machinist, maybe you can get one made. All it would take is a piece of round bar stock just smaller than OD of balancer snout, a couple of inches longer than the distance from where the balancer snout butts against the crankgear, or whatever is the positive stop for balancer on 250 six. Then, in a lathe, drill all the way thru with a hole the size of tap drill, and drill from other end to the depth from positive stop to end of crank with a easy slip fit diameter.
    Then when you need to pull the key and slide this drill guide on and go to work! Use a starting tap to help you keep the tap straight, and follow up with a bottoming tap.
    And yes, as Trucked Up said beware of breaking off the nose of installation tool in the crank snout! Make sure you use a GOOD QUALITY installation tool, not some cheap Chinese shit. Not a place to use cheap tool.
  25. Dapostman
    Joined: Apr 24, 2011
    Posts: 294


    If you know someone with a lathe, create a drill guide, a piece of 1018 round stock ½ inch larger than the crank and about 2 ½ inches long will work fine drill it to the size of the tapping drill and then bore it to a depth of half the length of the stock, slip it over the crank and drill through the center it will keep the drill centered and straight. It doesn’t have to be precision to work, just close works fine; most basement machinist can make this in a short amount of time.
  26. BJR
    Joined: Mar 11, 2005
    Posts: 6,993


    How about hold the drill against the crank and start the engine and let it idle while you drill it straight in? Wouldn't that keep it going in straight?
  27. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,912

    dirty old man

    I need to know more about where you are and where you do your work. Cause I don't want to be any where near you when and if you do stuff like this!
    Budget36 likes this.
  28. Only if you are holding the drill straight to start with.

    Let me add some experience with press fit balancers, normally when they come that way from the factory they work fine without a bolt. They are a little more difficult to install, you have to first make sure that the can snout is not swelled on the end and that it is burr free. You also have to get them going on straight or they will make their own burr as they go on. We used to run the guts out of the old 283s with press fit balancers and no bolt. never tossed one, granted we didn't know any better and you know that they say, "ignorance is bliss." We were some of the blissest SOBs on the planet.;)
  29. RMONTY
    Joined: Jan 7, 2016
    Posts: 2,204


    ^^^ What he said!
  30. sunbeam
    Joined: Oct 22, 2010
    Posts: 5,273


    Maybe the rubber bond didn't like the oven.

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