NC crank key

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NC crank key

Postby JohnT019 » Thu Apr 24, 2014 4:53 am


I'm in the process of building a strong bottom end for my NC with a 2.5L block. Using low compression Carrillo rods and CP pistons prior to adding an HKS SC. Target 15psi and max rpm 7400.

The crank engineers are suggesting that using two woodruff keys for the timing sprocket and the front pulley rather than a single straight key as per Cosworth and others.They are also saying that the loose fit (2 thou) of the OEM sprocket and pulley should be made an "interference fit" buy metal spraying the crank nose.

My view is that the OEM (robot friendly) friction fitting may require the loose fit and that the key should be added as security rather than an alternative method to a correctly torqued new nose bolt.

Brian I would be grateful if you could add anything to help me decide on the best course of action.


Brisbane Australia
330WHP MX5 NC 2.5L HKS Supercharger Plus lots of Goodwin go faster bits - Brisbane Australia
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Re: NC crank key

Postby Brian » Thu Apr 24, 2014 11:09 pm

Hi John

I appreciate the challenge that you face on this decision, and am sorry that I am not up to the challenge of the question you offer. I too depend on engine builders for these decisions, I too am a guy asking the builder, not the engine builder myself. Thus, I am sorry that I am not able to offer help on this one, I would talk to more engine builders and see if you can find a consensus.
Brian Goodwin
Good-Win Racing
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