Crankshafts

Old May 9th, 2018, 08:53 AM
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Crankshafts

So I have a few 455 blocks Ive been sorting through and have a question:
I disassembled two blocks one 68-72 and the other was later.
Comparing the two Cranks they are different and want to know exactly what they are? I think one may be a 4 spd crank and don't know much about these casting #s etc...
What is a Nodular crank? Is it a brand or type? and how do you tell the diff between forged and steel?
Which one is better and why?
I also have a couple 425 blocks on with a crank which I think is steel?
I include pix of the 455 cranks side by side. One has a big N so I assume its the Nodular?
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Old May 9th, 2018, 09:36 AM
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Nodular cast iron is a type of metal that is typically used to make things such as crankshafts that need increased ductility. The nodular graphite particles remove the stress concentration areas that occur with graphite flakes that are used in other types of cast iron, which makes the nodular iron more resistant to failure. As far as I know, all cast cranks are nodular cast iron.

Forged steel cranks have a V shaped notch on the crank flange whereas the cast cranks have more of a U shaped notch. Forged steel is stronger than nodular cast iron.

All of the 64-67 330, 400, and 425 cranks were forged steel.
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Old May 9th, 2018, 10:30 AM
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Originally Posted by scrappie View Post
So I have a few 455 blocks Ive been sorting through and have a question:
I disassembled two blocks one 68-72 and the other was later.
Comparing the two Cranks they are different and want to know exactly what they are? I think one may be a 4 spd crank and don't know much about these casting #s etc...
What is a Nodular crank? Is it a brand or type? and how do you tell the diff between forged and steel?
Which one is better and why?
I also have a couple 425 blocks on with a crank which I think is steel?
I include pix of the 455 cranks side by side. One has a big N so I assume its the Nodular?

I would guess the one top right picture has the large N on the front weight. Those were not usually drilled very deeply like the later ones with smaller cn cast in them.

Those were often drilled deeper. But they usually do not have manual trans bearings installed in them. 1974 and Up maybe more years

The one with Large N seem to be more desirable / valauable
Here is a picture of a 350 crank I took yesterday it has the BIG N
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Old May 9th, 2018, 11:15 AM
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The "N" and "CN" cranks are both nodular and are both the same as far as desirability and strength. The crank with the deeper hole has been machined for a pilot bearing for a manual trans. The fact that one is an "N" and one is a "CN" is unrelated to whether or not it has been machined.
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Old May 9th, 2018, 02:53 PM
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Thanks for the lesson guys!

Ken when you say crank flange are you referring to where the keyway is?
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Old May 9th, 2018, 03:42 PM
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No, where the flex plate bolts up.
Also, the early (64-67) cranks have a different bolt pattern than the later (68-up) cranks, so you have to use the appropriate flex plate / flywheel.


Here's a picture of the notch on a forged crank. I said a V shaped notch but it's more like a check mark.


Last edited by Fun71; May 9th, 2018 at 03:50 PM.
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Old May 9th, 2018, 06:00 PM
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caste

Originally Posted by joe_padavano View Post
The "N" and "CN" cranks are both nodular and are both the same as far as desirability and strength. The crank with the deeper hole has been machined for a pilot bearing for a manual trans. The fact that one is an "N" and one is a "CN" is unrelated to whether or not it has been machined.

They are both cast iron
The CN cranks that have funneled through here all been drilled like his pictured
There is no bearing retention clip groove or any evidence of a bushing being installed either
Not a manual trans crankshaft
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