BMW S65 Longblock | Better than Stock, High End

The Partee Racing BMW S65 longblock gives E9X M3 (and swap!) owners a stronger and cleaner foundation than a stock rebuild. We build this Better Than Stock S65 for serious street cars, track cars, and race-ready dry sump applications. We start by boring the block to 94mm on our RMC V40 CNC. This allows us to run our proprietary 2618 alloy pistons, made for us by JE Pistons. The piston design raises compression to 12.5:1 and supports our race-tested BMW S62 piston ring package. The S65 uses Alusil cylinder walls, so the cylinder finish matters. We use a specialized honing process on each cylinder. This process re-exposes silicon from the aluminum substrate. We then confirm the surface finish with a digital profilometer. We check Ra, RvK, RpK, Mr1, and Mr2 before assembly. This level of measuring helps us create the right cylinder wall finish for ring seal, oil control, and long-term durability. We pair the pistons with Carrillo or Arrow rods. We inspect, straighten when needed, and polish the stock crankshaft. BE or ACL bearings complete a bottom end built for high-rpm use and long service life.

Better Than Stock BMW S65 Longblock Details

We computer balance the full rotating assembly to within 1 gram. We deck the block and each cylinder head only as much as needed. We also use a high Ra finish to support proper head gasket sealing under demanding use. The cylinder heads receive a competition four-angle valve job. We clean and recondition the stock valves, seats, and retainers. We also install Partee Racing proprietary valve springs for better control at high rpm. If the valve guides fall outside specification, we replace them with motorsport-quality guides for an added cost. We do not guess on critical wear items. We measure, inspect, and build the engine the right way. We replace every one-time-use stretch bolt, tensioner, guide, chain, gasket, and key consumable with authentic BMW parts. During assembly, we blueprint every critical clearance and specification. We can provide the blueprint sheet to the customer upon request.

Race-Ready Dry Sump S65 Engine Option

Additionally, dry sump configurations are an option for the S65 BTS High End variant. This version adds dry sump race preparation for customers who need a stronger oiling solution, which is debatably all of them. The dry sump setup helps support sustained high-g use on track. It also makes this BMW S65 longblock a serious foundation for race car builds. We finish the engine with the same care we put into the machine work. We powder coat the valve covers in wrinkle black. We also ceramic bead blast the exterior covers and pans to restore a clean aluminum appearance. This is not a cheap auction-site rebuild. It is a precision-built S65 engine package for owners who want strength, reliability, and room to grow. Price does not include the $4,500+ core charge, if applicable. Please review our Core Charge Policy before ordering.