Cast Crankshaft Failure?

[JedIEG]

I have always heard that you need the swap the cast crank for forged unit due to their tendency to fail under shock loading. I hear this all the time in magazines and online, and I agree forged units are stouter, but I have never heard a real story of someone breaking a cast crank. Anyone what to share their experience?

 

[lewtot184]

almost all cast crank failures that i know of were manual trans cars, especially small block chevys. if you have an automatic they're easier on cast cranks. the grain structure on cast metals makes them prone to cracks and breaking. ford has always used a lot of cast cranks but i think the hipo stuff was nodular iron which is a little more forgiving. i wouldn't be afraid of a cast crank with an automatic at moderate power levels. i have a ford buddy who raced cast crank stuff for years. he told me he kept them away from high rpm and he never had an issue.

 

[mopar 3 B]

I have had a 440 cast crank break at #3 main journal. Had a knocking sound in it for years. New crank and no knock.

 

[RT K_line]

Well I ran a cast crank for years with no issues in one of my 440s. It was spun up to 7000 rpm on several runs, with the heavier six pack rods and pistons. I usualy shifted at 6800 rpms. I finally broke a rod running nitrous, but the crank never failed.

 

[Longroof]

I use to run cast cranks in my bracket car. 360 12:1 motor 7200 rpm with a fairly light rod and piston. They would crack. I Never broke one but they would crack. I bought a forged scat crank and never had another problem. Car ran low low 10's. Can't help you on 440 cast crank .. I never ran one.

 

[Garys1969RR]

I have heard that 440 cast cranks are good to 600 Horse power. I wouldn't run one with a 4 speed, as far as a drag race car goes. Automatic below 600 horse should be ok.

 

[dvw]

We run a 800hp turbo 360 with the stock block and cast crank. Going on year three, no issues so far. I also run about 450 hp through a stock 360 with a 4 speed, 15 years.
Doug

 

[JedIEG]

I find it interesting that there seems to be only cracking and not catastrophic failure. Has anyone broken a short throw cast crank? (318 or 400)

 

[moper]

I've never seen a broken Mopar cast crank. I know some guys have but some guys break forged stuff too. They do sometimes have trouble balancing if you are like me and internally balance everything. But they don't break easilly. If you've got an auto trans, and plan anything under 500hp, I'd have no worry running it assuming you do internally balance it. Internal is a lot easier on the parts.

 

[mopar 3 B]

I have a 383 steel crank not broken just bent beyond turning in the block. They will all fail if the conditions are right.

 

[Cranky]

I think that Mom's cast cranks are generally better than what the others were. I've run them too but not anything with high horsepower but beat the snot out of them on the street turning fairly high rpm. I've seen a fair amount of broken Ford and GM cast cranks for sure tho. Heck, the only engine that's ever blown up that was mine was a GM (265) and that happened right after I sold the car

 

[Hemirunner]

 

[JedIEG]

Well that is more like it. Could you post close ups of the break and surrounding area? When did it brake? What damper were you using? Accessories? Fan?

 

[Tbone416]

I have seen both broken. How much power are you think of make is what you should ask your self. I think you would be hard pressed to brake a 440 under normal use.