Crank/Harmonic Balancer story...

Discussion in 'Engine Topic' started by dizzle, Aug 30, 2011.

  1. dizzle

    dizzle Member

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    Feb 13, 2009
    fairfield, california
    Ok heres the long story...I finally got my car running the way i wanted it to. 77 camaro sbc 327. Headed up to Sac Raceway for a test and tune session, threw some 110 in the car and popped the hood to do a nuts and bolts check. Turns out my blower belt was riding on 2 of the 10 ribs (weiand 144). Anyways, I ran the car to see what the problem was and it appeard the harmonic balancer was moving slightly. So I let the car cool, grabbed my socket and started to loosed the crank pulley bolt and it broke off. Well after weaping to myself for a while my buddy helped load my car on his trailer (which is when the lower valence got smashed off).

    The next day upon examining the crank and harmonic balancer it appeard that the balancer was loose previously to me buying the engine. The engine probably has less than 1,000 miles on it. There was no visible damage to the crank and the only damage to the harmonic balancer was on the keyway, where it looked as if it was the only thing holding it on.

    So I measured the crank and it came out to 1.240 and the balancer was 1.245. I talked with ATI and they would have to make a custom balancer to fit this crank (over 500 the guy said and 6-8 weeks for delivery)...With the crank being so small was it machined when the engine was rebuilt? Does anybody know where I can get a balancer that size? And lastly how would you approach your mechanic who built this engine and did not catch this?:(
     
    Last edited: Aug 30, 2011
  2. Cardinal

    Cardinal Veteran Member Lifetime Gold Member

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    Jun 22, 2003
    Endicott, NY
    I'd approach him with a BFH in my hands and give his melon a new dent!

    How in the name of Zora Arkus-Duntov could anyone assembling an engine miss the fact that the harmonic balancer on a SBC is a PRESS FIT!

    IMHO, your machinist should be replacing the crankshaft for FREE.

    I googled the internet to find out what the crank shout should measure and the consensus of what I found is that it should measure 1.244" to 1.245".
     
  3. Damon

    Damon Veteran Member

    12,866
    9
    Nov 16, 2000
    Philly area
    I've never heard of anyone machining a crank snout after the factory did their thing on it.

    Part of me wants to think that the older cranks (like a 327) might have a smaller diameter snout than later stuff but....... nah, I don't think so.

    Here's an idea.... many aftermarket performance/SFI-approved balancers are intentionally undersized and designed to be machined to fit. Without machining they are often too tight to install. But in your case that might be exactly what the doctor ordered. Now, I don't think they are 5-thou under, but they are tighter than a stock replacement. Might be worth a shot to see if works. Buy one local and see if it's tight enough to require a tool to isntall it. If so, you're probably good to go. If it just slides on by hand then it's definitely time to think more deeply about a solution.
     
  4. Jim Mac

    Jim Mac Veteran Member

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    Dec 28, 2004
    tucson az USA
    I know your running a small blower but when I did some research putting a 6 71 on my camaro, I was told I needed a crank hub because the stock balancer would end up getting trashed because its cast. Could your balancer gotten loose or twisted on the crank spinning the blower?
     
  5. dizzle

    dizzle Member

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    Feb 13, 2009
    fairfield, california
    thanks guys! i think i will try to pick up a high performance one tomorrow. i would hate to see my crank go to waste. not to mention all the work ahead of me...this engine doesnt even have 1000 miles on it yet. ugh first it was the blower problem and now this...i have some pretty bad karma built up
     
  6. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

    8,699
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    Sep 20, 2004
    Southern Maryland
    I have run later style balancers on an early 327 (1966). It has the same size snout as the later SBC's. Actually the only thing holding the early balancers on WAS the press fit...the press fit alone should keep it on there without a bolt.

    You could potentially use Loctite sleeve retainer products. They claim to fill up to .006" gaps and the stuff is really tough but that would in my eyes at least be a last resort, no-other-options fix.
     
  7. dizzle

    dizzle Member

    59
    0
    Feb 13, 2009
    fairfield, california

    I will grab this just incase it is a little to big...perhaps i can at least get one pass in friday. My first time at the track (ever) was with 3.42 gears, everyday tires, and no posi...13.4 @ 114. so if i can improve a second or so on that i will be satisfied....
     
  8. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

    8,699
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    Sep 20, 2004
    Southern Maryland
    I have to buy it from industrial supply stores. I have never seen an auto parts store carry the loctite sleeve retainer products (they are quite different from the thread retainers)
     
  9. dizzle

    dizzle Member

    59
    0
    Feb 13, 2009
    fairfield, california
    The balancer was loose and that was why the blower belt was slipping off, the lower pulleys were moving slightly. I had a fluid dampr on it p/n 712615-003. I looked for that part number and it appears they dont have that one, but they do have a similar one just different p/n.

    More to follow...ordered some of that loctite stuff and will order a balancer now.

    When measuring the crank should you measure the inside or the "just the tip?"
     
  10. mrvedit

    mrvedit Veteran Member

    1,346
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    Jun 12, 2009
    Ann Arbor, MI
    Sorry if this is obvious or insulting, but with something this strange, I would be sure to measure with a (2nd) micrometer and not just a digital caliper.
     

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