The stock crank seems to hold out fine to 1000 HP w/stock maincaps it seems.
Guys in Brazil have done it,anything over 1000 HP, then they mod the maincaps by adding w/steel straps.

The weakest link to the 250 or Standard blocks,(230,250) is the left hand front corner head bolt area,they tend to crack,or in Douglas's case exploded that corner piece off,he was making a 8.0 pass when it blew up before the finish line. & ran an 8.6.
Leos book is good to read & get info about the Chevy L6's.
You can get it through this forum or other members I believe.
http://www.amazon.com/Chevrolet-Inline-S...93599912&sr=8-7

RPM wise, people go to 7000-8000 RPM with a built engine & seem to hold together.
My supercharged 250 liked to turn to 7000+ rpm & never broke.



MBHD

12 port SDS EFI