Has anybody here broken a BB chevy cast crank, or know anyone that did?
Got into a little heated discussion with my mopar friend on how much abuse a cast BB crank would take. I told him I would pose the question and he says," do you think anybody would be stupid enough to admit they overloaded their crank? "
I said "stupidity has nothing to do with it, were a team! Team Chevelle. We share information, good bad or ugly."
I hope knowbody has broken one, but if you have, what do you think the cause was. How much torque or HP do you think the engine made?
I'm thinking 600hp would probably be the limit. Any body think differently?

Oddly enough,
BBC's seem to hurt forged cranks more often than cast ones.
The forged cranks carry harmonics worse, but some of the failed forged ones I've seen have lived a hard life too..

I've run 3 big blocks with cast cranks,keeping the rpms under 6500 and have never had a problem with crank,rods or pistons. I've never blown one up and I've tried,,,3 full years of racing on my current one,ran nitrous on the last one, and the first one I drove from california to missouri with 4.11 gears and 26" tall tires smile.gif

my cast crank stock rods 468 has handled several 275 nos shot and 6 years of hard servive in my 3600 lb nova. its been 10.90's on motor and 9.60's on spray

I know RR floggs his ride, but
10.90s w/275 nos shot @9.60s is more than I expected.

So much for that theory.

Thanks!

I think this winter I might gain another 100hp.
:D

Somehow.

PS
Thanks for your input Jake.
I never thought of it that way, but if a tree doesn't bend.....

The old timer machinist that did my shortblock said the same thing. The forged, nitrided, cross-drilled, etc 7118 L88 crank was cracked in 5 places!

Machinst said that a cast crank RARELY cracks.

Neverthless I found a grungy old 6223 crank which was std/std and mint when clean. He preferred forged here due to compression and rpm, but was quick to add that a cast would have been fine.

The problem with both the forged and the cast is they both have a fatigue life.

You never really know what they've been through.
Also any machinign you do to an object adds stresses internally to the material.
There are ways around this.
Seasoning..
We've all heard of it.
Seasoned blocks.

In the world of ultra-high performance stuff the engine parts are machined and then de-stressed.
Common techniques are some type of virbratory equipment.
You can shotpeen, use a very high frequency vibrating table that the parts are attached to, or ultrasonic stuff.

But for our stuff the best way is to just start with a NEW crank.
You can buy NEW GM 6223 forged 427 cranks from www.competitionproducts (http://www.competitionproducts) for $250 or blems for $150.
I hear the blems usually take a polish, they have a nick or something that once polished won't affect operation..

Last December a friend of mine broke a stock cast crank in his 1990 454 SS truck. Very mild engine. It did have alot of miles on it ( 200k+ on the crank) but was never raced ... just a daily driver... just one of those things that happen

BBs are not hard on cranks cast or forged. Your friend is a Mopar man they do have crank problems (oiling for starters) and anything you can do to make the crank better is a good thing.

Have seen many a Broke and/or Cracked cast BBC crank but they've all been in truck's and tractors used by local pulling yahoo's. I'm talking 500 + HP stood on their heads at 5500-6500 RPM's under incredible load! Personally I think that's awesome for any cast shaft, including industrial.

Originally posted by Mike Feudo:
Your friend is a Mopar man they do have crank problems (oiling for starters) and anything you can do to make the crank better is a good thing. Boy he isn't gonna like hearing that. ;)

I just purchased a BBC Chevy crank from Comp Products.
The journals are tapered and too small, also out of index.
It was only $200. and for that money I will get it reground.
This was not a blem.