In the 500+whp realm, the factory M57 cast aluminum pistons and powder forged cracked cap rods start to become a wildcard. Billet or forged aluminum pistons would have been a simple solution to handle the power short term, they cannot be made with a steel top ring land and consequently will only live 30-50kmi on the street. A steel piston will outlive all other internal engine components.
Viewing the opportunity for leaps and bounds to be taken instead of simple steps, WPI is bringing the best possible bang for the buck to the market. The first few sets are nearing the final stages of production and will be running in engines as quickly as possible after that!
To help reduce side thrust loads, the connecting rods were lengthened by 10mm center to center which reduces maximum rod angle by just shy of 1 degree. The wristpin was also dropped from 30mm to .990" which is the stanard big block Chevy size used in top fuel dragsters. The production connecting rods will be made by Molnar Technologies. Prototype rods pictured were made by Pauter Machine.
The wrist pins are .290" wall thickness and being made by Precision Products Performance, the main wrist pin supplier to NASCAR teams. The pins are then receiving DLC coating done by Northeast Coating Technologies.
The pistons themselves are being investment cast and cnc machined from 4140 steel in Indiana. Cast 4140 steel is at a bare minimum of 3x stronger than the best possible cast aluminum. The pistons are designed with an oil cooling galley with matching ports for the factory oil jet. Combustion bowl geometry was kept the same as OEM, but valve pockets were deepened by .020" for extra piston to valve clearance with aftermarket cams. Once finished, the pistons are receiving abradable skirt coating and cermaic dome coatings from Line2Line Coatings.
The pistons use the OEM M57 ring pack, they will be supplied with Goetze rings. Perhaps the biggest design bonus is that the steel piston and wrist pin are actually ~65g lighter than the oem aluminum piston and wrist pin! Added up across all 6 cylinders, that means over 375g will be removed from the reciprocating mass inside the engine.
The package price includes the coated steel pistons, spiral locks, DLC coated wristpins, Molnar connecting rods, Goetze rings, and Kolbenschmidt connecting rod bearings.