Don't think anyone knows the exact sort of figure. I reckon they could hold 275bhp of daily constant use. The revs will hurt them more.
Why would the revs hurt them?
We are revving to 7850rpm on my Lesley's RS2 clio and it does LOTS of trackdays etc and no problems at all.
Its torque that they cant take IMHO more than anything else.
Mine have VERY clearly been killed by torque in the turbo not revs, as revs stretch rods not bend them shorter!
I view the sensible limit as being roughly at the 250ftlbs point that MWM do their turbo conversion for, although one thing to remember is that these rods are poorly made mass produced cast rubbish, and as such they vary in my engine all the rods had seen near identical loads and yet 2 were still fine, 1 was bent slightly and 1 was proper banana'd
