Texas Jim

I noticed in the tech section that it states the "Nodular" cranks are in the '68 to '70 455 ci engine and then the "regular cast" are in the '72 and up. What crank is in the '71 455 4bbl. in the Olds 98? Thanks in advance.

cutlassefi

I just pulled apart a 72 455, had an N crank in it. But I've seen 2 different types, a CN and an N, some had all the rod throws drilled some did not. Still haven't figured that out yet.

dc2x4drvr

Trovato say's in his book that most of the '68-'72 big blocks were equipped with a nodular iron crankshaft,(some were built with forged steel) and '73-'74 cranks could be either nodular or gray iron. Nodular iron cranks are identified by a large 'N', or 'NA', or small 'ca' cast into the #1 counterweight.

cutlassefi

It's a small "cn" on the front counterweight.

dc2x4drvr

Guess Bill needs to fire his proof reader..

507OLDS

I would throw-out that tech page.
If it's not a 68 455 steel crank,it's a nodular crank.They can have a large N,smaller CN,NAK,or a few others.They all have the same casting number.If they were really different,they would have separate casting numbers,like the steel crank does.Some of them are machined differently in the rod journals,but that's about it

88 coupe

Classic Olds "tech section" is a "copy & paste" from 442.com, which is well known to contain numerous errors and myths.

http://www.oldsmobilewiki.com is based on the same source, but much of the misinformation has been (and, hopefully, continues to be) corrected.

It seems the “regular” or “grey iron” myth (started by the same parts salesman that gave us the solid main web 403) is still alive and well.

Prior to the availability of nodular iron (during the '60s) all automotive crankshafts were forged steel, which were replaced by cast nodular iron as soon as it became readily available.

If a “grey iron” crank actually existed, and was installed in a fresh 455 rebuild, it would probably not survive the cam break in.


In this case Trovato was misinformed.

Norm

J-(Chicago)

If you get an N crank and a CN crank side by side, the CN crank will have noticeably different machined grooves on the ends of the journals.

88 coupe

Foundry (casting) and machine operations are totally unrelated.

The following would fit standard operating procedure in that manufacturing environment.

The "CN" might be added to identify that crank as a specific engineering update. The crank would then be ground according to a matching "CN" blueprint, and a corresponding part number assigned.

Norm

J-(Chicago)

That was my thought process as well.
Welcome back.

507OLDS

Same material,so therefore same casting number.

88 coupe

1. The configuration of a mold is not related, in any way, to the material that is poured into it.
   
   
2. Casting numbers (part of the mold) and part numbers, as assigned to the finished part, are also unrelated.
   
   
3. Stamped letters/numbers, punched into a machined surface, would be an entirely different topic.

Norm

507OLDS

I guess what I was trying to say is that "IF" the N-crank was any better or different than a CN or NAK,then there would be different casting numbers.The 68 455 forged cranks have their own casting number.
Unless it is a 68 455 forged crank,ALL of the other 455 cranks are the same.There isn't one stronger than the other.Yes,there are different cuts in the journals,but when it's all said & done,they will all explode at the same limit,if given the exact same components.There was a lot of false information posted & published in the 80's & 90's,and some people are still holding it as gospel,while others have gone out & proved the facts.
We could get into the same discussion about the nickel content in the Olds blocks,but NONE of them have enough nickel to get excited about.They are all within a certain variance.Believe it or not,the Olds blocks have more nickel than some of the original SBC & BBC blocks.We don't have any Mexican 302's,like Ford does,and we don't have Dart blocks.We are racing dinosaurs.

BlackGold

Maybe, maybe not. I agree with Norm that they might decide to change an alloy (not just for cranks but for any other part) and not change the mold.

Remember, the casting number is not the final part number. Just as the same casting might be machined 5 different ways and receive 5 different final part number but still show the same casting number (as with camshafts), cranks could be cast with different alloys and thus receive different part numbers but still display the same casting number.

88 coupe

Again: Casting numbers (and those N, CN, NAK, etc.) characters were formed by the molds and are not related, in any way shape or form, to the iron alloy that was poured into them.

How would one go about adding a "casting number" to a forging?


Back to the opening post:

To be more accurate: If it is not forged steel, it is cast iron. Nodular (ductile) iron was used in all cast cranks.

Without documentation those "codes" (N, CN, NAK, etc.) previously mentioned are worthless.


And back to the original question:

Doesn't matter. Have it magnafluxed and if it is good, use it. The important part is to take care in your choice of crank grinders.

Norm

507OLDS

OK.You're getting it now.Whatever crank is in the block,use it,as long as it is good.I have done a bunch of different tests on these cranks & blocks,of all different years,and there really is no difference,or better piece,from one to the other.Is that better?
I know some of you are looking for the certain better piece,but there isn't.