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Old 03-19-2009, 02:57 PM   #1
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Default Converting for short nose to long nose.

Does anybody know where I can get the long or big nose (I believe its a 27mm snout) crankshaft? I am looking into swapping out crankshafts so I can run the billet OP gears. I have everything I need but the crankshaft itself. I am just looking for maybe a link to a site that might have some or even a forum member who would be willing to sell one. Any help is appreciated.
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Old 03-19-2009, 03:08 PM   #2
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Read a bit from this article;

Miata Crankshafts

Here's a direct quote from the above link;


There are 3 crankshafts for 1.6 liter engines. Some people mention "short" and "long" when they really mean "short" and "big". Watch for this when you search archives. The crankshafts are the short nose, long nose, and big nose (Figures 1, 3, and 5 respectively). The short nose is fitted on early cars, the long nose is available primarily as a service part for those cars before the VIN cut in 1991. The long nose crankshaft is directly compatible with a short nose engine with no additional parts swapping required. The short nose and long nose use the same pulley bolt and torque. After the VIN cut, the big nose crankshaft is fitted with a bigger bolt. The nose of this crankshaft is larger diameter so a different engine front cover/oil pump is needed. The new oil pump has a bigger hole through the georotor to fit over the larger crankshaft. The big nose bolt has a larger threaded diameter, large shoulder diameter, and higher tightening torque. All of the bolts have 21mm heads.

Also the short nose crankshaft uses the lower timing belt cog as a structural member, that is the cog is bolted to the crankshaft, the accessory pulleys (one v-belt and one serpentine) are bolted to the cog. The timing belt cog, in addition to its timing belt rotational duties, must support the rotational and bending forces of the accessory belts. After the introduction of the big nose crankshaft, the timing belt cog has only one job, to rotate the timing belt. Mazda introduced an additional part they call a "pulley boss" (Figure 5). The pulley boss is a sturdy cast hub that forms a mounting flange on the front of the crankshaft. It is bolted to the crankshaft. The timing belt cog is bolted to the back of the boss and the accessory pulleys are bolted to the front of the boss."
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Old 03-19-2009, 04:57 PM   #3
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Ok so what I gather from that is that for me to swap to the big nose I need Big nose crank, big nose oil pump, big nose crank pulley assy., and bolt? Or am I missing something?
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Old 11-05-2011, 10:12 PM   #4
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Back from the dead. Have the same question. What are all the parts that are needed for swapping in big nose crank?
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Old 11-06-2011, 03:59 AM   #5
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I did this. The engine block is the same. Oil pump is different. Pulley asssembly is also different. Just check the part sheets and select the parts for the later engines.

Last edited by IHI; 11-06-2011 at 04:00 AM. Reason: Typo
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