I'd be surprised if he replaced an entire bottom end, although I guess it depends on what he means by 'blown'... usually new pistons and block are required as my crank and rods have survived each of my engine failures...
I'm not sure what the differences would be between the 406 and 306 bottom ends, I've heard rumours of 40mm big ends, as opposed to 45mm big ends that I have, and I would guess at lighter piston designs as the ones in mine are fairly standard looking Omega ones, certainly not out and out race pistons!
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Oulton Park in a BTCC 306 vid 1Oulton Park in a BTCC 306 vid 2
Lap of the 'ring