MED EN40B STEEL BILLET CRANKSHAFT - MINI

Whilst standard crankshafts can be effectively re-worked to improve their counterbalance effect, it is not possible to add material, only subtract. You're also unlikely to know the history of a second-hand crankshaft - it could be over 60 years old!

Yes - standard 1275 Mini crankshafts weigh between 11.5kg-12kg, and this weighs just 10.5kg. A heavily modified factory crank could potentially weigh less, however, but it is unlikely to have the weight in the right places for the benefits of strength and balance.

No, it's not required, as we have moved the oil way drillings compared to the standard crankshaft. For high RPM use on standard A-Series crankshafts, it was always necessary to cross-drill the big end journals, relocating the oil ways to help reduce the chance of oil starvation to the bearings.

Our crankshafts are manufactured just 20 minutes from MED at Arrow Precision Engineering - the very best in the business! We've worked with Arrow for over 20 years to create the best possible product.

The big end journals are sized at 1.625" as per the original Cooper S, so standard S rods will fit if you're able to find a set in usable condition. Alternatively we would highly recommend upgrading to a set of MED steel conrods for extra strength and considerable weight savings. Main bearings are the standard 1275 size, 2.000" diameter, and thrust washers are also the standard 1275 type. We can supply a complete crankshaft, piston, conrod and bearing package if you prefer.

We've tried both and have found no tangible difference in strength and reliability between the two manufacturing techniques. Our preference is to have crankshafts CNC machined from EN40B steel billet, as this allows for regular design development without needing to make a new forging tool each time, which would not be economically viable.

Unfortunately it is not viable, cost-wise, to have a one-off special produced. Sorry. We do keep 86mm stroke crankshafts in the Multiweb Mini design, if you wish to build a 1460cc engine. Otherwise, these are the standard 81.3mm stroke.

Absolutely. Each crankshaft is supplied with a test report, fully balanced, 100% crack detection and with certification of material and heat treatments. Critical detail inspection reports are also supplied. There is an incredible amount of work involved in producing, machining and testing each crankshaft, using Arrow Precision's 50-plus years of specialist experience.

This crankshaft will likely withstand higher RPM levels than the A-Series engine will as a whole. Typically on the most severe over-revs, usually changing accidentally from fourth to first gear, the valve train will fail first. We would not recommend testing this! We would recommend, however, a set of MED steel main caps and studs to better support this area of the engine block, if planning to rev the engine regularly to over 6000rpm.