After months of development we are proud to introduce the ultimate M20 2.9L street-stroker pistons. We worked with Mahle Motorsport to design and produce a stroker piston that would offer OEM-like reliability and longevity without sacrificing performance.
–Use with the M20 “885”-style cylinder head.
–85mm Bore (+1mm bore over stock)**Never have your block machined prior to receiving your pistons. Any good machinist will insist that they have the pistons in hand prior to boring the block.
–10:1 Compression (This is 91 octane friendly with proper tuning).
–84mm Crankshaft Stroke (M52 crank for example) *not provided
–135mm Connecting Rods (M20, M52, S52, or length-specified H-beams) *not provided
These pistons are specially made using Mahle’s proprietary M142 Forging Alloy. Other alloys require larger piston-to-bore clearances (like the 2618 alloy) or end up sacrificing strength (like the 4032 alloy). This alloy combines the strength of the 2618 alloy with the lower required piston-to-bore clearances needed with the 4032. The M142 alloy is used on several high-performance OEM applications (like the LS engine in the Corvette Z06’s).
— Each piston dome is CNC machined to match the correct OEM style offset dish so as to maximize quench.
— Deeper valve pockets have been cut into the domes to accept more aggressive camshafts (however you should ALWAYS double check your piston to valve clearance prior to starting your new motor). Can be used with oversized valves.
— These pistons feature “slipper-skirt” side skirts which reduce friction and reciprocating mass. This is a feature found on later model bmw pistons.
Each piston is phosphate coated. This acts as a dry lubricant, and helps to reduce wear during your initial start up or engine break in. In addition, each piston has Grafal coating on the skirts. This coating is meant to reduce drag, friction, scuffing, and cylinder bore wear.
We use Mahle Motorsport PowerPak ring sets and wrist pins (included). End gaps and other specifications are provided in the MahleMotorsport information pamphlet.
You can download instructions here.