The symptoms of a 3 bearing crank failure?

[Dennis Nicholas]

The broken crank photo from Ruairidh seems to illustrate grossly negligent grinding of the crankpins! Some years ago I read a book on the development of the BMC B engine (A50, A60 MGA etc) Increasing the radius from .060 to .090 had a huge beneficial effect on fatigue life. Jowetts discovered the same, although their need was more desperate! Reconditoners have undone nearly all

Further development on the A+ 1275 (1300) crank gave it a rolled fillet radius between big end and web.  That is instead of the big end surface and the web surface at 90 deg meeting with a radius, there was a rounded depression put in...rolled fillet radii.  However the drawings had to be strictly adhered to, as otherwise, as Leyland found out, reliability was compromised so production varied and some had rolled and some not until the full problem was sorted.
(mind we are talking about using the A+ at 6,000 to 8,000 rpm for racing)

(I found luckily I have one of the properly done cranks and as I will not be using such revs in the Nippy I should be safe for a very long time) 

Dennis