BMW S85 Stroker Kit for M5 and M6

Our stroker kit can be made at any stroke. Our suggestion for most applications is 83mm. Other strokes can be custom ordered and we can assist with engineering rods and pistons to complete your custom kit. Typically we will design a kit for each specific engine build, we work with CP pistons along with Carrillo rods to create a package that will work with the stroke that you choose. We take everything into account to design the ideal rotating assembly for your specific requirements. Whether that be lightweight high rpm road racing or a strong forced induction bottom end, we will design the rotating assembly around your requirements. The crankshaft is then balanced using the weights of the rods and pistons that we design for your specific kit. This method allows us to create a balanced bottom for ideal performance. Each one of our kits is engineered specifically for your application. As with our other billet crankshafts these 10 cylinder cranks are plasma nitrided, and dynamically balanced.

Using a billet crankshaft is expensive but it allows us to save significant weight over the stock crankshaft while the billet crankshaft gives superior strength to the OEM forged crankshaft. Being aware of the tight clearances on the OEM S85 engine for both main and rod bearings we add an additional .0005" clearance by cutting our main and rod bearing journals smaller. If looser clearances are required we can advise on bearing choices to accomplish that.

We have two versions of this kit, the first, more economical kit works if you have a good condition block. We are able to use the original bore and create a custom CP piston with the proper coating to work with the BMW Alusil bore. The downside of this is you cannot overbore the engine. The more expensive, way to build this stroker kit is to use our custom designed sleeves to press into your block. This allows us to use a standard aluminum piston at the expense of the added machining cost to install the sleeves. More importantly it also allows us to use a larger bore, up to 94mm. This allows us to achieve over 5.8 liters of displacement. Sleeving can be done by us here along with complete assembly if required

This kit includes:

• 83mm Billet Stroker Crank
• (10) Carrillo Rods custom built for your specific application
• (10) CP Pistons for a Sleeved Block, compression ratio chosen by you

For any other configurations please contact us for options.