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Project Subaru EJ25 - Part 2

Rise of the Phoenix, Part 2

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Performance Tolerances

Katsu Hibino, formerly of Cosworth USA, machined the block to accept the new JE pistons as well as measuring the rod and main bearings for proper clearances. We finalized our Cosworth rod bearings at .0019 clearance, a bit on the looser side but sufficient enough for our plans when we track the car on the weekends.

Another overlooked area when building an engine is to measure thrust clearance. Even with a new set of bearings this should always be checked.

Engine Assembly

Shingo Yugami of Bluemoon Performance, located in Costa Mesa, CA, carefully took measurements of each cylinder/ring to achieve proper piston ring gap before using an electric grinder. The type of driving and power output you plan to put your engine through will determine your ring gap. Consult your piston manufacturer for proper gap specs.

Royal Purple and ARP Fastener Assembly Lube

Assembly lubes like Royal Purple Max-Tuff prepares potential wear surface and prevents metal contact before adequate lubrication can be supplied. Because of frictional inconsistencies with oil, moly, and other lubricants, it takes multiple cycles of torquing the bolt, loosening it, and tightening it again to obtain the required preload or stretch, causing inconsistent values. ARP Ultra Torque assembly lubricant is marketed as a lubricant for bolts that needs to only be torqued once to get within 5 percent of ideal preload, and it remains consistent through all subsequent cycles (from race-prep machining through final assembly).

ARP Stretch Gauge

Using a stretch gauge delivers the most precise and accurate way to determine the proper preload, or torque, on a connecting rod bolt. Our ARP rod bolt stretch gauge allows you to accurately measure bolt stretch as opposed to a torque wrench that relies on "friction" at its highest value when the fastener is first tightened. The torque wrench method is often found to be inaccurate and inconsistent when using an improperly calibrated wrench.

Always clean any parts prior to assembly. We recommend using a 4-to-1-ratio mixture of warm water and Simple Green cleaner. Using a soft bristled brush, lightly scrub the surface, paying close attention to bristle the piston ring and oil groove channels. Finish it off by blowing it dry using an air compressor.

Rebuilding an engine isn't cheap but you should never cheap out on your build by reusing seals. It is imperative to use new seals regardless of how new or clean they appear.

Too much silicone sealant can become more harmful than good for your engine. Why? When too much silicone sealer is used, the excess portions will ooze out and can block oil and cooling passages as shown in our image, which leads to overheating. We used a small brush to evenly apply the silicone.

Cosworth Oil Pump

The Cosworth blueprinted high volume and pressure oil pump helps increase the oil volume to help prevent bearing damage and engine failure. This unit is important when the engine is sustained at high rpm, which has been known to cause oil starvation at the rod and main bearings.

JE FSR Pistons

Forged pistons are a must for Subaru motors producing more than 400 hp. The heat and stress high-boost applications produce can destroy a stock Subaru cast piston over time. JE 2618 alloy forged pistons offer superior strength and durability-far more resilient than stock cast pistons. We used a set of +. 25mm 99.75mm pistons with an 8.5:1 compression ratio. When it came to installing these bad boys, we looked no further than ARP. Companies like ARP offer an alternative and much smarter approach when installing pistons with their tapered ring compressors. These hard-anodized aluminum sleeves have a smooth radius that tapers down to the specific bore size. The design allows compression of the piston rings without damage and can be installed with a simple push of your fingers.

ARP Head Studs and Cosworth Head Gaskets

ARP Custom Age +625 head studs offer superior yield and tensile strength (260,000-280,000 psi) over previous ARP model L19 studs to eliminate blown head gaskets from high boost. We combined the +625 head studs with a set of Cosworth high-performance MLS head gaskets.

ATI Damper

Unlike undamped underdrive pulleys, which offer no protection to high-performance engines, the ATI Super Damper provides balanced damping of torsional crankshaft vibrations at all rpm levels. The OEM crank pulley has an elastomer (rubber ring) sandwiched between a central hub and an outer metal ring. This torsional damper type dampens vibrations and should never be replaced by non-damped units. All ATI Super Dampers exceed SFI 18.1 Safety Certification and are approved for competition use.

Stay tuned as we finalize our build in the next issue with some go-fast goodies including a Full-Race turbo kit and UK-manufactured adjustable cam gears that are sure to give this engine some serious boost in performance.

Automotive Racing Products
1863 Eastman Avenue
CA  93003
JE Pistons
15312 Connector Lane
Huntington Beach
CA  92649
Royal Purple
One Royal Purple Lane
TX  77365
3031 Fujita St.
CA  90505
King Engine Bearings
327 Little Falls road, Suite 5
Cedar Grove
NJ  07009
ATI Performance Products
6747 Whitestone Road
MD  21207
Bluemoon Performance
3032 Enterprise Unit F
Costa Mesa
CA  92626
WPC Treatment
2909 Oregon Court
Unit C2
CA  90503
Revco Precision
6114 Cherry Avenue
Long Beach
CA  90805
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