Race Spec Shortblock

The Race Spec series short blocks are designed and built for the demands of motorsport. The block is CNC machined and fitted with Darton sleeves. Darton sleeves are a stepped thick wall design manufactured from ductile iron. The strength of the material combined with the greatly increased wall thickness compared to stock (particularly at the upper portion subjected to the greated pressures) results in a significantly stronger and more rigid cylinder. By maintaining its shape under the most extreme pressures, it allows the ring seal to be maximized and performance and reliability to be maintained under power levels far exceeeding the factory block's capabilities. The Pro version takes things a little further with the addition of ARP block hardware. To correct for any distortion of the main bearing bores, the block halves are line bored.

The Race Spec series feature Omega forged 2618 alloy pistons. Omega brings F1 piston technology to the masses with exceptional accuracy and quality control. This is a lightweight slipper skirt design with an excellent balance between low inertia and strength/rigidity. Connecting rods are RalliSpec-exclusive in a high strength 300M material forged in the USA and fitted with ARP Custom Age 625+ bolts. A state of the art lightweight billet crankshaft from Cosworth is provided.

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 for the most extreme applications. 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 new head studs and high quality RCM "folded stopper layer" head gaskets. A further option is to machine the block deck and fit copper o-rings to provide additional pressure on the head gasket fire ring (can be done with or without oversized head stud option).

Every block is assembled by our highly experience engine technician with 18 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 chart.

Usually ships in 4 to 8 weeks.

Manufacturer: RalliSpec

Applications:

• Subaru WRX STI MY15-17
• 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