so far every 100mm crank that is making good power without fluidamp is breaking. some are breaking within 1000 miles

 

Aaron has told me the same. They see the OEM cranks crack right where the OP's broke. Its worth the money to step up to a forged eagle crank. Buy the time you source a 4g64 crank, polish it, and balance it, you're pretty close to an Eagle. $200-$300 isn't a huge difference to prevent the carnage we see here. OP got lucky, this could have been a windowed block, ruined head, etc..

 

Manley forged: knife edged and balanced. Old school Fluidamper. No balance shafts.

I spin it over 9000rpm every time at the track since 2012. So countless times. I've logged it at 97XX rpm.

As far as I'm concerned a manley forged crank is cheap as dog**** when looking at a full build. I'm always scared it's going to let go, but never has. I wish I'd done a billet originally.

 

That is an untrue statement the 4g64 cranks are known to be good to 600 torque over that your pushing your luck.

 

i was making 580. it didnt last much

 

Don't think your super safe running Manley billet, English racing steers clear of them. I tried to get one for my build and they very aggressively talked me out of it.

Even went as far to show me the box of broken Manley billet cranks they have lol

 

i ended up getting a forged manley ;/ its something to get the car up and running

 

Yup. ER recommends eagle forged or K1 billet.