Mesa Balancing Racing Engines uses a GM remanufactured 1 piece rear main seal block which is steel shot prepared magnetic particle inspected and fully blueprinted by machining every critical machine surface first we align hone second we parallel deck then we finish the cylinders with a torque plate to the proper finish and piston to wall clearance for the pistons being used. When the machine work is completed we debur the bottom of the cylinders hand wash the block and only then is the block ready for preassembly. All crankshaft and components are inspected and individually balanced. These engines are built to order and for specific applications so when you order if you're going to run boost or NO2 please let us know so we can clearance the pistons and rings accordingly. We can also build to a long block with either a custom camshaft for your application or your specific camshaft. These engines are built for you and not a production assembled. All engines use 4340 forged crankshafts your choice of I beam or H beam rods HP series rod and main bearings dura bond performance cam bearings.