Vega

Can i get the skinny on this story?
Ive read the tech section but theres not much there

Vega

It may be blasphomous to ask but being forged could you get more offset out of one of these cranks safely as opposed to a standard nodular iron crank?

citcapp

I have bought one and then sold it after weighing it. It is heaver then the nodular crank by about four pounds creating more rotating mass. After discussions with my engine builder I sold it and went with the nodular. I believe you would be better off with an aftermarket forged crank that is lighter if you want to go with forged. Just my opnion

bigD

it would certainly be stronger than the nodular iron crank but i don't know how to quantify it. even offset ground you don't see or hear of too many of the nodular cranks breaking...

Vega

Hm, i ask because i may have stumbled upon one, i know theyre extremely rare and stronger than cast iron, i also know ive never heard of a cast iron 455 crank breaking, theyre crazy strong. Would be cool if it did turn out to be a forged crank though

Vega

Thought id post this question on my existing thread so i dont feel like im spamming

How far can you safely offset grind a stock N crank? And forged cranks are stronger so in theory couldnt you offset grind a forged crank even further? And if so what would anyone recommend? I know 507Olds and CutlassEFI would most likely be able to answer this for me pretty easily

507OLDS

Any production 455 crank can be offset ground to 4.500" with a BBC rod journal,nodular or forged.I have always sold the forged cranks and used a nodular.I've never had a problem with one.The crank for the 507 was absolutley mint,so we were able to squeeze 4.550" stroke out of it.It is nuodular as well.
On another note,you can NOT offset grind a 400/425 crank that far.The max offset for those is 4.2975",if you want to get technical.This is also with a BBC rod journal.You could squeeze 4.300" if you're lucky,or use an undersize BBC bearing.

Vega

Thanks 507Olds! Every bit of info gets me that little bit closer to visualizing my build. And im sure there are others out there who have wondered or will wonder in the future what the max off-set is, hopefully they stumble onto this.


AND NOW THE VERDICT ON THIS WHOLE ADVENTURE:
The first two pics are of the crank in my 68' block, the left pic is of my cast iron crank. Notice the difference in the cut-out of the crank flange. Forged steel it is!

TripDeuces

My research goes like this:

Early 68 (not model year of Sept. but Jan. Feb 68) B body (98 or Delta?) with two barrel carb and possibly the tow package. It makes no sense to me but I've seen stranger things.
Vega's first two pics are a forged crank with the 'L' shaped cutout. They are easy to spot from the casting marks parting line or lack thereof also. Unmistakeable.

Vega

Thanks! Yes, this was a Feb motor, actually i think it was the very last day of Feb in 68', 2-barrel, was told it came out of a cop car. Small valve C heads and lower compression pistons for 68'. Not sure why they would choose to give forged cranks to the lesser motors but hey, it happened apparently lol

Im most likely going to sell this one, so if anyone is interested let me know, i turned the motor by hand today and it almost turned too easily, everything kept rotating while i was trying to take the flywheel bolts off haha

507OLDS

Those cranks were totally random,as far as what they were installed into.They were made in the early run of 68's,for a few months.They are fairly rare regardless.They are also not the same forging,or same material,as the earlier 400/425 cranks.

64Rocket

The two that I have come across came from a 455 low comp, 2 bbl, full size Olds.

Gene

Vega

That seems to be the general idea, dont think ive heard of a forged crank coming from a 4-bbl yet. I believe my motor is from a Delta

Once i get the crank out it will most likely go up for sale, but who knows, with how people are dismissing these and going straight to aftermarket i might very well just keep it, if not to use then at least for a very cool collector's item :-)

bigD

the first one i had came out of a low compression, early ('68 or '69) 2bbl low compression motor...

the one that i have now came in a high compression short block that i bought from Earl Reynolds in Mt. Pleasant, IA.

that man had some damn nice oldsmobiles!!

young olds

my 68 delta custom with "98" engine option, 455 4bbl, had a forged crank.

young olds

bringing this thread back. I just tore down a 455 down and found a forged crank in it. Wondering how it stands strength wise vs a 4.25" stroke 425 crank?

507OLDS

The 400/425 cranks were a better material than the 68 455 forged cranks.

Octania

This '68 Toro 455 had a forged crank:

https://lh3.googleusercontent.com/-k...d_CN03-VIN.JPG

VIN 38M811649

Army_Vet

I just rescued a 1968 W34 Toronado engine from the scrap man to the tune of $300. Turns out it has the coveted forged crank. The block has a cast date of 78 (March 18, 1968) and the car was built in the 4th week of March. VIN derivative on the block is 38M617696 and the VIN is 394878M617696.

olds 307 and 403

I wonder if the change in material was a cost saving measure? Didn't they close that forging plant? Funny the 330 cranks must have switched in late 67 to nodular as they have been found in untouched motors.

Smitty275

Forged is stronger than cast nodular iron.
There are no aftermarket forged.
Cast nodular iron is much cheaper.
Many people have had cast nodular iron crankshafts fail. Often with catastrophic results.

AK71CutlassS

In what use are they breaking??? Im putting a "Cn" Crank in . I don't need to worry do I?

Smitty275

All depends on how your going to use the engine. If its a street machine you'll be fine. If its something your gonna race then it depends on the power level, trans brake or not, bottom end upgrades or not, healthy converter and big tires, etc.

I won't build an engine for a customer with a factory nodular crank if it's going to have a trans brake or power over 550hp. Yes, I've lost business over it. But I also have piece of mind that no one is going to be upset when it eventually breaks under either of those conditions. And if religiously abuse it failure will occure.