Our Stage 1 fully built street series shortblock supports up to 500bhp 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.
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 Type RA Semi-Closed Deck Block Case, Cosworth Forged Pistonsw/ Xylan Skirt Coating, RalliSpec H-Beam 4340 Forged Rods by Saenz, ARP2000 Rod Bolts, ACL Tri-Metal Main Bearings, Calico-Coated Clevite Rod Bearings, Nitride Hardened 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 warranty for the engine? This information along with break-in process details can be downloaded here: Engine Warranty & Break-in Instructions (PDF). We fully stand behind the quality of our short blocks but there are many factors outside of our control that will contribute to or detract from the reliability and life expectancy of the engine. Poor tuning, improper or lack of maintenance, failure to select the proper supporting components for the power output, or engine cooling issues are often the culprits behind many engine failures. However, we understand the frustration a customer might experience after investing a significant amount into a built engine only to have it fail. Therefore, we will provide a one-time 20% discount on any replacement shortblock when a failure does not meet the requirements of our warranty coverage. Only the original purchaser is eligable to obtain this discount and only within 2 years of original purchase date.
What is the compression ratio? The compression ratio depends on the head gasket thickness and cylinder head combustion chamber volume. With a factory head gasket thickness the compression ratio is approximately 8.2:1 with B25, N25, W25, and V25B cylinder heads and 8.6:1 with D25 cylinder heads. If the heads have been milled then the compression ratio will be slightly higher depending on the amount of material removed. A head gasket thicker than 0.6mm will lower the compression ratio depending on how thick it is.
What engine block casting is used to assemble the engine? We have no choice in the selection of the engine blocks. We purchase the current engine block part numbers available from Subaru.
Do you use the nitrided factory crankshaft? Subaru has switched between nitriding and induction hardening processes for their crankshafts. We currently use the nitrided crankshaft.
What is the balance process used when building this short block? We weight match the pistons assemblies to within 1 gram of each other using a milling machine to precisely remove material from the least critical locations. We also weight match the connecting rods to within 1 gram end to end removing material only from the least critical locations and polishing the weight removal areas so as minimize any stress risers. We retain the crankshaft dynamic balance as supplied from the factory. The option to precision balance the crankshaft is available for an additional cost of $200 by special order. However, often times the majority of the imbalance in a rotating assembly is due to the clutch and flywheel assembly because of the signficant weight and its distance from the rotational centerline. If dynamically balancing the crankshaft, the best option is to ship to us or purchase from us the clutch, flywheel, and crank pulley so that all these components can be precision balanced at the same time.
Is the block honed? The block is not honed unless we find excessive distortion or an inability to achieve our desired piston-to-wall clearance within a tolerance of +/- 0.0002in. The price of this block does not allow for this machine work unless absolutely necessary. Each piston and bore is measured to a precision of 0.0001" using specialized equipment and pistons selectively matched to each bore in order the achieve optimal clearance. Rest assured this short block is far beyond the "drop in piston" short blocks competitors are typically selling.
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 we suggest an 11mm oil pump. Piston-to-wall clearances with the Cosworth pistons are 0.0025in +/-0.0002in.
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 flow rate of the turbo, 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.
Can I substitute different pistons or rods? Our engines have been developed using what we believe are the finest components available within the target price range. In particular, when selecting pistons and rings for our Street Spec engines we took into account the desired characteristics of low noise, maximum longevity, and reduced blowby/oil consumption under typical street use drive cycles. Although we are happy to build a short block or long block to your specific requirements if you feel strongly about a certain setup, we treat any deviation from our standard engines as a custom job with more limited after-sale support. We feel that our off-the-shelf engines represent the best possible combination of components and processes.
