Our Stage 2 fully built street series shortblock supports up to 700bhp with proper tuning and supporting modifications. Our short blocks are race proven for durability and reliability. The street series is built for low noise, minimal oil consumption, and is designed to last years (not months like some of our competitors). Cosworth's specially developed alloy allows piston clearances to be kept low while the boxed-strut forging design and short pin length ensure the strength and stiffness necessary to withstand high power levels. Each short block is assembled from new parts in a dedicated clean environment by our two in-house builders with a combined Subaru race engine building experience of over 30 years.
Our Street Spec Pro Value is our entry level closed deck daily driver short block option. A closed deck block utilizes cast aluminum inserts press fit into carefully machined areas of the block face to reinforce the highly stressed upper area of the cylinders as well as stabilizing the deck surface. Depending on power levels we recommend either ARP2000 (up to 550bhp) or ARP Custom Age 625+ head studs together with either RCM head gaskets or Athena cut ring head gaskets. Every block is precisely diamond honed to size while fitted with torque plates to replicate the assembly distortion. A final plateau hone ensures fast and consistent ring break-in.
Every build goes through a rigorous ultrasonic cleaning, measuring, and assembly process with each measurement logged for future reference. Components are weight matched and carefully machined and polished as required to achieve the desired tolerance. Bearing clearances are measured with calibrated Mitutoyo micrometers and precision Sunnen dial bore gauges and adjusted to within +/- .00015" by substituting bearing shells. Piston ring gaps are hand filed to within .001"of the target clearance which is based on the intended use and expected power levels. Low tension rings utilizing ring gaps developed through our extensive experience ensures reduced oil consumption and blow-by while keeping ring friction to a minimum.
The components used in this short block are as follows: EJ257 Fully Closed Deck Block Cases, Cosworth Forged Pistons w/ Xylan Skirt Coating, RalliSpec H-STD (H beam) 4340 Forged Rods by Saenz, ARP2000 Rod Bolts, ACL Tri-Metal Main Bearings, Calico-coated Clevite Rod Bearings, Nitride Hardened 79mm Crankshaft, Block Plugs & Covers Included.
One year limited warranty when professionally installed and registered
Click here for shortblock comparison and specification chart.
Click here for warranty and engine break-in information.
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).
At what power level is a closed deck reinforced block necessary? We receommend any application above 450whp be utilizing a reinforced block due to the extreme cylinder pressures and increased possibility of detonation. Applications in the 400 to 450whp range may not absolutely require a reinforced block from a failure prevention standpoint but may see advantages in ring sealing and overall longevity.
Will a closed deck block run hotter? The addition of material around the top of the cylinders can cause that area of the cylinder as well as the piston and perhaps the cylinder head to run somewhat hotter due to the extended path between the cylinder/piston and the cooling jacket. However, this is offest by improved ring sealing through decreased cylinder distortion. Also, the material and fitment of the inserts ensures the best possible heat transfer rate under the circumstances.
Do you use the nitrided factory crankshaft? Yes, the current crankshaft we are using is nitrided which increases the surface hardness or wear resistance of the crankshaft.
What is the balance process used when building this short block? Street Spec Pro Value short blocks have pistons matched to within 1/2 gram and rods matched end to end also within 1/2 gram. Material is carefully machined from non-critical areas and polished to minimize stress risers. Improving on the dynamic balancing of the crankshaft cannot be effective unless the clutch,flywheel, and crankshaft pulley are balanced together with the crankshaft as an assembly. For this reason we do not precision balance the crankshaft dynamically unless we have all components on hand (at additional cost)
Is the block honed with a torque plate? Yes, we always fit a torque plate during the honing process to simulate the distortion created by the cylinder head bolt torque. For this shortblock the torque plate is installed using ARP2000 head studs and RCM MLS head gaskets unless otherwise specified.
What clearances are used for piston-to-cylinder and for crankshaft bearings? The clearances we use are based on extensive testing and experience. Rod bearing 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 an 11mm oil pump for best results. If power levels and application information is unknown we set the piston clearances on this short block to .0028" (+/-.0001").
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. However, we do not suggest exceeding 24psi on normal pump fuel(petrol) in a street driven application due to variability in fuel quality and the inability to consistently control knock/detonation conditions above this pressure. With quality race fuels or high ethanol percentage fuels boost pressures can be set depending on turbo performance, supporting modifications, and type of use with less concern for destructive knock and detonation conditions.
What is the maximum rpm of the short block? There are many factors to consider when establishing a maximum rpm for a particular engine. Of greatest importance in determining this is the oil supply conditions. The oil flow from a factory oil pump will start to noticeably decrease at rpms in the 7500-8000rpm range depending on the pump, while oil pressure requirements at the rod bearings are increasing due to rotational forces opposing oil flow from the mains the rods. Utilizing a dry sump system is necessary for reliable operation much above 8000rpm for any extended period of time. Running a billet crankshaft with direct shot oiling may also be required. Additionally, the valvetrain must be capable of supporting the desired rpm range. Of most importance is to set a maximum rpm that is no higher than necessary due to increased wear and stress. If you set a maximum rpm range well above where the engine and turbo setup are capable of making good power then you are increasing the stresses on the engine for no reason.
Can I substitute different pistons or rods? Our engines have been developed using what we believe are the finest components available and most suitable for the application. While you may reach out to us for a custom build, keep in mind that we will provide no warranty or additional support when you select components that are not recommended by us.
