RalliSpec LogoRalliSpec Group N Car at LSPR
> home / catalog / engine assy / short block / rallispec race spec value subaru

Race Spec Value Shortblock

The completely redesigned Race Spec Value now features a closed deck block design to withstand extreme power levels. The top of the cylinders are reinforced with inserts precision machined from cast aluminum to exactly match the expansion coefficient of the base block material. The reinforcement prevents cylinder expansion, distortion and potential failure of the upper cylinder wall during extreme cylinder pressure conditions. The "pro" closed deck version features additional reinforcement of the block bolt access holes utilizing threaded inserts to partially close of the holes after block assembly.

Every short block is professionally assembled in our dedicted engine building room by our in-house builder who has over 20 years of motorsport level Subaru engine experience and has built hundreds of Subaru high performance engines. Every short block is blueprinted to carefully designed specifications that balance extended service life with extreme power capabilities. Every dimension is logged and a build spec sheet is provided for reference.

This short block is built uses Manley 2618 Extreme Duty Turbo Tuff Series pistons. The extreme duty pistons feature a heavy wall pin that reduces flex under extreme power outputs. We fit our Pro Series connecting rods in a 4340 material and ARP2000 rod bolts. The crankshaft spins in King XPG tri-metal bearings for optimum reliability. The block is precisely bored and finish honed with torque plates for straight and accurate cylinder dimensions. The cylinder crosshatch and piston ring end gap specifications ensure fast break-in and minimal blow-by conditions. The block decks are machined to correct any deck height errors and provide a surface finish for optimum head gasket sealing. The block is assembled with all necessary block hardware and oil separator plate.

Several optional upgrades are available to increase head gasket sealing. A 1/2" head stud package increases the head stud/bolt size from 11mm to 1/2" for additional clamping force. A 14mm head stud package further increases that dimension. The block is machined to accept the larger head studs. Additionally, you must send your cylinder heads to us so the bolt holes can be machined oversize as well. Each package includes the appropriate ARP oversized head studs.

Click here for shortblock comparison chart.

Usually ships in 3 to 4 weeks.

Manufacturer: RalliSpec

Applications:

  • Subaru WRX STI MY15+
  • Subaru Impreza STI MY01-14
  • Subaru Impreza WRX MY06-14
  • Subaru Legacy GT MY05-12
  • Subaru Outback XT MY05-09
  • Subaru Forester XT MY04-13

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).

How does closed decking the block compare to sleeving? The closed deck process adds reinforcing inserts around the top 1/2" or so of the cylinder. While this is typically the most highly stressed portion of the cylinder owing to the fact that the combustion pressures are highest when the piston is just slightly below top dead center, the remaining portion of the cylinder is still unreinfoced compared to the standard block. Sleeving, on the other hand, uses thick walled high strength cast iron cylinders to strengthen the entire length of the cylinder. The two processes are used to achieve a similar goal but with two entirely different approaches.

What is the balance process used when building this short block? Race Spec Value short blocks have pistons matched to within 1/2 gram and connecting rods matched to within 1 gram end to end. The crankshaft is dynamically balanced to 0.25 oz in.

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. 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 our standard process is to use ARP standard head studs torqued to 90ft-lbs with an OEM head gasket.

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 value are set to approx. 0.0035".

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.