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    Small nose crank failure...

    How many of you have had this happen? I'm reconsidering attaining a big nose if I'm gonna be putting big power to the engine... don't wanna have the key sheer off.

    Damn, now I'm gonna have to get a different pulley and timing gear... what else would I need to change?

    JoN - Automotive Machinist Journeyman/Refrigeration Mechanic Journeyman
    Member of MX-3.com
    1996 Mazda MX-3 RS - Creek Blue Mica
    1993 Mazda MX-3 GS SE - Raspberry... RIP


    Racing BP (Project "Blue" Marlin)... Twin Scroll GT3071R, breaking 30psi at the moment!

    "Do it ONCE, do it RIGHT!"

    #2
    actually, it doesn't *seem* to be too common amongst the FWD short-nose motors. search member 'Tweaks' - he posted some pics of his failed short-nose. on the other hand, the forged short-nose from my original motor looks flawless with 225K miles on it.........

    if building a motor - esp turbo - I would say find a big-nose to be safe. you'll need everything that attaches to the snout of the crank: pulley, key, gear, bolt......
    Original owner: 1991 Protege LX (now w/SOHC) and a few more BG's ....

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      #3
      The small nose failures as i understand it came from improper torque of a bolt that was NOT designed for such a high torque. So basicly BEFORE it happens you replace the bolt with a brand new OEM Mazda bolt and install it with the PROPER torque spec and viola no more worrying!

      PS: It happend on my 89 tracer/323 that i still drive as a beater. I had the "shaky" crank pulley syndrome and from reading random info that is a sign of it just starting to loosen up. So i started taking it all apart one day and managed to take the crank bolt out with just one hand on my socket driver! Ie it must have been just about ready to fall out and cause alot more damage! Anyways. Replaced the bolt about hmm maybe 20k ago now and its still fine as the key didn't get to wear out that much during that brief time of the crank pulley being slightly loose.
      Last edited by Tazman2; 03-22-2006, 08:55 AM.
      **SOLD** 93 EGT with more suspension mods then your average riced out civic's # of decals + useless "bling/style/culture" mods! **SOLD**
      95 EGT New beater! And gawd damnit shes NOT pink!

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        #4
        Ok good to know... thanks fellows! I did a little more looking into it and found that article on miata.net. It appears that I have the later miata vin code pulley, so that problem should be fixed. I may appear I have the big nose after all... gotta go to work and measure the thing.

        I think I got all confused with big, small, long, and short. I think it's the short big nose crank that fails... as in it's short and fat kinda big, and the bolt has very little flare. And the long small nose crank that's good... as in it's long and thin with the extended key and keyway, with the a bolt with a big flare.

        JoN - Automotive Machinist Journeyman/Refrigeration Mechanic Journeyman
        Member of MX-3.com
        1996 Mazda MX-3 RS - Creek Blue Mica
        1993 Mazda MX-3 GS SE - Raspberry... RIP


        Racing BP (Project "Blue" Marlin)... Twin Scroll GT3071R, breaking 30psi at the moment!

        "Do it ONCE, do it RIGHT!"

        Comment


          #5
          Hmmm... Theres only two that i know off. The small one (pre 92) and the bigger one that comes on 92 and up cars from what i recall. What year is your car? I may be blind but i don't recall seeing it!
          **SOLD** 93 EGT with more suspension mods then your average riced out civic's # of decals + useless "bling/style/culture" mods! **SOLD**
          95 EGT New beater! And gawd damnit shes NOT pink!

          Comment


            #6
            Originally posted by Shades
            Ok good to know... thanks fellows! I did a little more looking into it and found that article on miata.net. It appears that I have the later miata vin code pulley, so that problem should be fixed. I may appear I have the big nose after all... gotta go to work and measure the thing.

            I think I got all confused with big, small, long, and short. I think it's the short big nose crank that fails... as in it's short and fat kinda big, and the bolt has very little flare. And the long small nose crank that's good... as in it's long and thin with the extended key and keyway, with the a bolt with a big flare.
            I know its confusing

            The 'short-nose' cranks came in the B6 + BP untill mid ~1991. I have no idea of the VIN cut-off for the Protege...... the Miata has gotten a lot more attention due to seemingly more failures than the FWD motors.

            The 'long-nose' crank is/was an available FACTORY FIX for a B6 'short-nose' motor that failed. AFAIK, they did not make a 'long-nose' replacement for the BP......The 'long-nose' crank did not come on any Mazda motor.

            The 'big-nose' crank replaced the 'short-nose' in mid 1991.

            So *if you have a short-nose BP*, AFAIK the only option you have is to source a 'big-nose' and the associated pulley parts.
            Original owner: 1991 Protege LX (now w/SOHC) and a few more BG's ....

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