Alfaholics Long Stroke Crank – 2000 Nord & Twin Spark

In designing this crank, we started from scratch using modern knowledge of optimum crank design and CAD to design the optimum crank for the Alfa 2000 Nord and Twin Spark engine.

We stretched the stroke of the crank to the maximum possible whilst ensuring the crank fits the block without modifications, this has increased by 5.5mm to 94mm, which gives just over 2100cc with 84.6mm bore, or just under 2300cc with 87mm bore. Our development engine has produced 15BHP extra with this crank versus an original Alfa crank. This results in Twin Spark engines producing 230-240BHP and Nord engines producing 220-230BHP.

In designing the crank we were very conscious to remove any weight where unnecessary, and thus the big ends are specially bored hollow to reduce centrifugal weight. The counterweighting has been optimised with very specifically shaped and sized webs to ensure perfect piston/rod counterweighting at high revs, something that the original Alfa crank is rather poor at. The result is a long stroke, increased capacity crankshaft that revs up faster and is more free revving than a factory crankshaft.

After the billets are turned they undergo a stabilising process where the billets are reheated and left to cool, this removes any of the machine stresses and further improves the qualities of the material, once the cranks are finished milling they undergo an internal rumbling process that deburrs the machined surfaces and also assists with further de-stressing of the material.

Crankshafts are pre and post-nitride CNC ground for accuracy and control of journal sizes as well as nitriding case depth uniformity. Gas nitride hardening achieves a bearing surface hardness up to 900 Hv to approx. 0.5mm.