Gary M

need a quick education on which is the best way to go for a 455 4 speed car. May need spelling lesson too. Billet 🤔

joe_padavano

Both "CN" and "N" cranks are nodular iron and are the same. A steel billet crank is far stronger and more expensive. For a street-driven car that might see only occasional track use, the nodular is more that adequate.

wr1970

You could go with a forged crank. I agree with Joe P. on the above post.The billet crank is the best and cost the most. Did you ever get the mondello crank problem resolved yet?

GOSFAST

If you get an OEM crank try to get one from a dedicated "stick" car, some are not set up for the pilot bushings. There were many more automatics produced than standards!

Can't recall how many we ended up boring the backs for the pilot bushings, probably done a few dozen over my years in business??

Thanks, Gary in N.Y.

P.S. Wishing all here a Happy New Year!

android 211

Most Olds cranks are NOT drilled for 4 speed use. The machinist I use charges $150 for the service. If you are concerned about strength then search out a '68 455 crank. Most are forged. Only '68. There is a notch on the rear flange that identifies them for sure. For street use and only occasional track use any factory crank will be fine.

Gary M

i got another one from him that looks good but I talked to a machine shop we've used for 25 years and a testing lab. Both say they have never heard of 5340 steel so I'm not going to use it for my build. It's probably fine but I'm going to sell it. A member on here has a N ak crank and a CN crank that need turning priced right. I'm very tempted to buy the billet crank though now that I know more about it.

joe_padavano

AMS5340 is the military designation for a stainless steel used primarily for investment castings. It's also known as 14-4PH. It has 130,000 psi tensile yield and 149,000 psi tensile ultimate strength.

For comparison, the nodular cast iron used in the factory cranks has a tensile yield (depending on the specific nodule size in the casting) of between 47,000 and 95,000 psi and a tensile ultimate of between 67,000 psi and 130.000 psi.

Gary M

but from all the bad things I've heard about this Lynn guy I am not confident it really is what he claims. Is it possible that a crank containing military grade stainless would only cost 600.00? Maybe and very well could so if it is what he says whoever buys it from me is going to get a good deal. Just haven't got around to posting it yet.

joe_padavano

I certainly can't speak to the quality of this particular part, or if it really is the material claimed. I can just provide the specs for the material. Bottom line is that it is still cast, though stainless steel is less prone to internal casting flaws than iron. The reality is that strength is less important than fracture toughness and casting quality. AMS5340 should be better for that, but I'll put money that this is a Chinesium casting, so be skeptical of quality or even material properties.

Gary M

Bet if I looked through the box it came in I'd find some newspaper packing w/Chinese writing on it. I walked past it with an egg roll the other day and I could swear it moved.

It should be fine for an automatic car.