Tech Advice! Modifying crank nose

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topcatcustom
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Tech Advice! Modifying crank nose

Post by topcatcustom »

Hi again, on my Nash the crank nose is very short, approx 24mm from the front of the cam drive sprocket to the end of the shaft, before the diameter reduces and a thread is machined on. The original nut is present that is wound onto the end to tighten the front pulley. This arrangement is not great for me as the 24mm is not long enough for good support, I am proposing to machine in effect a nut with a finished round outside the same diameter as the shaft, when permanently fixed on I will have a much longer crank nose which will be good for supporting the blower and accessory drive pulleys.

Can anyone suggest why this may be a bad idea, or a better solution? I could have it built up with weld then ground down to size, but as the crank is so old I'm not keen on this. I intend to drill and tap the end of the crank to house a bolt to tighten the pulley up, like a RV8 crank.

Cheers in advance!

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TC

kiwicar
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Post by kiwicar »

Hi Tom
This looks like a good plan to me, however what are you going to do about a damper for the crank? it might be an idea to make the thing a little longer, cut a keyway into it and the bit of the crank nose you can get at and fit a chevy 6 1/4 or 8 inch damper over the joint between the two bits to lock the whole lot together and be better able to transmit the power to drive the blower, and not undo itself on the over run, or if the inlet coughs back into the inlet.
Another idea might be to make a long top hat nut arrangement, effectively have a parallel section as you have drawn but made out of hex stock turned down so you have something to hold a damper on with and then pin it into the crank from the front.
oh you will probably have to bore the hole in the middle of the damper a bit.
best regards
Mike
poppet valves rule!

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topcatcustom
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Post by topcatcustom »

Do you know big block Chevy nose diameter Mike? Can't believe the Nash is 35mm and rover front pulley fits perfectly!! However- I'd rather use a more manly damper than found on the rover- although saying that a lot of people over the pond reckon that a blower belt acts as a damper anyway so I may be ok with the smaller rover one and a 3" wide pulley!
TC

kiwicar
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Post by kiwicar »

Hi Tom
SBC crank snout is 1.25" (actually 1.255 for the interference fit)
The BBC is 1.61"
ford 360 is 1.375", about 35mm in Napoleons new fangled system measurements!
best regards
Mike
poppet valves rule!

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topcatcustom
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Post by topcatcustom »

http://www.ebay.com/itm/1980-95-Ford-7- ... da&vxp=mtr

This looks perfect apart from the taper on the back...

However- with the dry sump set up the oil seals should have an easy life..??
TC

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