The Race Spec series short blocks are designed and built for the demands of motorsport. The foundation of the Race Spec short block is a new EJ257 block case machined and fitted with closed deck inserts to reinforce the cylinders. We fit either a factory salt bath nitiride hardened crankshaft or an optional Manley billet crankshaft (recommended for operation over 7500rpm). Connecting rods are our tri-beam pro series rods in a 300M alloy and fitted with ARP 625+ bolts to support big power levels reliably. We use an RCM/Omega 2618 forged piston with DLC coated heavy duty piston pins. The crankshaft spins in low friction coated ACL tri-metal bearings while connecting rods are fitted with a Calico-coated Clevite bearing for maximum durability at extreme power outputs.
At minimum we suggest an 11mm ARP 625+ head stud and performance head gaskets but we also offer the block machined for 14mm RCM head studs (with a head side diameter of either 12mm or 14mm). Note that 14/12mm oversized studs can be used with factory head gaskets and unmodified head bolt holes but will be a very tight fit. 14/14mm oversized studs require drilling the heads and using gaskets with larger center holes. Modified or oversized dowels are required as well.
Every block is assembled by our highly experience engine technician with 20 years of Subaru motorsport engine experience. Assembly is done in our dedicated engine building room. We use highly accurate and calibrated equipment such as Mitutoyo digital micrometers, Sunnen 0.0001" reading dial bore gauges and setting fixtures, Ohaus digital scale with 1/100 of a gram accuracy, and Snap-on digital torque wrenches. Every measurement is logged and a detailed build spec sheet is supplied with each engine for your reference.
Click here for shortblock comparison and specification chart.
Usually ships in 3 to 4 weeks.
What is the recommended break-in process for the engine? This information along with warranty details can be downloaded here: Engine Warranty & Break-in Instructions (PDF).
I've never heard of Omega pistons, are they any good? Omega is a highly regarded yet very specialized piston manufacturer in the UK with experience developing pistons for racing teams running at the highest levels ranging from F1 to WRC to MotoGP. Their main focus for many years has been the European motorsports market so their reputation within the US, particularly among the street performance market, has not been widespread. The Omega forged pistons we are using are a lightweight slipper design precision machined from a 2618 heat treated aluminum. This alloy offers maximum strength and superior thermal conductivity (potentially reducing piston crown temperatures). This makes it the optimum choice for racing applications. Omega offer pistons with a level of quality and engineering far superior to other options of the market. Yes, there is a premium to be paid for this level of quality. However, we feel strongly that achieving maximum performance and maximum durability requires a no compromise approach when it comes to piston selection.
What is the advantage of the billet crankshaft over the factory one? The factory crankshaft is quite well engineered and has good strength at fairly low weight. It is forged with a generous journal fillet and will suffice for moderately high power levels. In more extreme applications the billet crank improves on the standard forged crank in many ways to maximize its strength and durability while reducing its rotational inertia. Most importantly, however, the oil passages are redesigned to improve the flow of oil between the main and rod journals particularly at high rpms where rotational forces are working against the flow of oil in the crankshaft.
What is the balance process used when building this short block? The Race Spec short blocks have pistons matched to within 1/3 gram and connecting rods matched to within 1/2 gram end to end. The crankshaft is dynamically balanced to 0.5gcm.
Is the block honed with a torque plate? Yes, we always fit a torque plate during the boring and honing processes to simulate the distortion created by the cylinder head bolt torque. We suggest you indicate to us what cylinder head hardware, torque values, and head gaskets will be used so we can most accurately replicate the loads. When this information is not supplied to us we will assume an 11mm ARP 625+ head stud.
What clearances are used for piston-to-cylinder and for crankshaft bearings? The clearances we use are based on extensive testing and experience. Oil clearances are increased over the factory settings to allow for significantly increased loads and component distortions. The engines require a 5W40 / 10W40 (road) or 10W50 / 15W50 (race) oil viscosity and a minimum of an 11mm oil pump. Piston clearances on the Race Spec are set to 0.0035" with factory crank and 0.0038" with Manley crank (we assume higher power outputs and sustained high loads).
What is the maximum boost pressure for this short block? We are often asked this question. Boost pressure on its own will not overstress an engine. Peak cylinder pressure after the spark plug fires will be significantly higher than any useable boost pressure. Increased boost pressures generally lead to increased cylinder pressures and heat loads which can overstress an engine. But the exact correlation depends greatly on the tuning, the type of fuel, and other factors. Its impossible to tell you what the maximum boost pressure the engine will handle will be.
What is the maximum rpm of the short block? There are many factors to consider when establishing a maximum rpm for a particular engine. Our shortblock comparison chart offers a suggested maximum rpm provided all other contributing aspects of the engine assembly have been designed to support that rpm. It is also important to understand that it makes no sense to attempt to increase revs if the engine's power is already falling off significantly or is running outside the efficiency range of the turbo. Additionally, there are often limitations in the factory oil and cooling systems that make significant increases in rpm unwise without a proper re-evaluation of those systems.
