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Thread: Crankshaft Rotational Freeplay - What's going on with this engine?

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    Crankshaft Rotational Freeplay - What's going on with this engine?

    In the process of tightening the fan belt and some rotational freeplay (about +/-10 to 12 degrees) in the damper / big crankshaft end nut was observed - early BJ-7. There is little to no "lash" or thrust - back and forth movement, only this rotational movement. The nut is secure and damper pressed fit nicely to crankshaft with no leaking oil from seal. Also, there is no movement of the distributor that corresponds the degree of freeplay. Other than this, the engine runs smoothly through RPM range.

    So the question: Is there an acceptable tolerance for crankshaft rotational freeplay? What's going on here with the engine?

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    Re: Crankshaft Rotational Freeplay - What's going on with this engine?

    It sounds like you are describing delamination of a harmonic balancer. There are places that say they can rebuild them. I think it's more common to replace them. On other makes of cars where this happens the owner is typically advised to stop running the engine until a fix is implemented. I don't know if the same holds true for A-Hs.

    See this old thread:
    http://www.britishcarforum.com/bcf/s...lancer-repairs
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    Re: Crankshaft Rotational Freeplay - What's going on with this engine?

    The BJ7's Harmonic Balancer is comprised of two parts, the laminated piece is bolted to pulley. Fanbelt runs off pulley and the entire assembly and nut have some degree of clockwise and counterclockwise movement.

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    Re: Crankshaft Rotational Freeplay - What's going on with this engine?

    Gonzo, I don't believe you should run the engine till this is fixed. I have never heard of rotational "play" in a crankshaft pulley or damper. If the whole assembly is moving then I would have to believe that the key in the keyway is sheared and the hub is not really tight on the snout of the crank.
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    Re: Crankshaft Rotational Freeplay - What's going on with this engine?

    Understood and I'll be investigating this further. First order of business is to spin off the nut, then check the pulley for movement. Thanks, GONZO

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    Re: Crankshaft Rotational Freeplay - What's going on with this engine?

    Gonzo, Vette is right, I would not run it as is. I have heard of this and I know of one fellow racer that had one 'fret' itself loose - the key and keyway can easily allow the rotation you describe. The pulley should be so tight that you need to boil it in a pan of water to install and ram home quickly. You may have the pulley worn oversize the crank snout worn undersize, or a combination of both. If indeed it is loose, it will get progressively worse.
    Are you certain the movement is between the pulley and the crank? I ask because sometimes there can be a small amount of rotational 'free' movement due to rod bearings clearances until you hit the resistance of rings in the bores. I can usually get some small relatively free movement back and forth with mine.
    Dave

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    Re: Crankshaft Rotational Freeplay - What's going on with this engine?

    I just checked and have less than a degree of rotational play, and that's probably in the timing chain.
    John, BN4

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    Re: Crankshaft Rotational Freeplay - What's going on with this engine?

    : Engine should not be run in its current state.

    Either the rubber is failing or the keying on the shaft is defective.
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    Re: Crankshaft Rotational Freeplay - What's going on with this engine?

    I would pull the balancer and check the crankshaft nose and the bore of the balancer. Generally if the balancer has been loose on the crank the woodruff key shows wear where it sits in the slot. All of this wear can add up to a fair amount of slop. It is my understanding through hearsay that the expensive Australian harmonic balancers on the market are tight as a "tick" on the Healey crank and coupled with a new key may solve the problem. I believe the crank end is harder than the balancer so it may not wear as fast as the hole in the balancer. One of these more competent fellas here may have the specs for the crank end circumference. As I am but a simple carpenter my word is suspect but I have seen this before. Best o luck, you are in excellent hands here. We are truly fortunate to have such knowledgeable folks in our midst!
    Last edited by elrey; 12-08-2017 at 08:38 PM. Reason: I am quite curious as to how to repair a worn crank snout since I have one in my collection that is too small to use. There was evidence of some form of tinfoil in the slot and the damper when pulled
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    Re: Crankshaft Rotational Freeplay - What's going on with this engine?

    "tight as a condom"


    ​I didn't know they were supposed to be tight!

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    Re: Crankshaft Rotational Freeplay - What's going on with this engine?

    \I would suggest you loosen the fan belt and reach down to the lower pulley, if it rocks freely this would mean it is worn or come off the wood drift key. If it is not loose than I would suspect worn timing chain or timing chain gears or worn timing chain tensioner. It will be one of these issues.

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    Re: Crankshaft Rotational Freeplay - What's going on with this engine?

    Damper doctor or damper dude to the rescue! https://www.damperdoctor.com www.damperdudes.net

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    Re: Crankshaft Rotational Freeplay - What's going on with this engine?

    Great ideas. Thanks all for sharing. Here's an update: crankshaft rotational movement is no more than 2 degrees with fan belt removed. When I replaced the seal last year the damper took some effort to remove with a three arm puller. It checked out OKay along with the crankshaft snout. The damper was warmed up (110F summer heated driveway), aligned it to the key and quickly drove home with a lead mallet. This took some effort as well. 75 ftlbs to tighten the crankshaft nut. I'm confident the assembly is secure.

    From your ideas, I believe the movement could be due to rod bearing clearances or timing chain. I'll investigate this further. GONZO

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