Since we last left off with our Subaru build, we repaired and upgraded our EJ25 cylinder heads with a set of Kelford R-199-B (264/260 duration) camshafts and Supertech valvetrain, and got the head massaged with the help of Portflow Design. After months of planning and installing parts, we have finally arrived at building the block. At this point, you may be thinking that this build is overkill for the average street car. We would resoundingly agree, but excessive planning and building is what is going to take us to our promised goal of netting respectable lap times at Buttonwillow Raceway in the near future. With a large portion of our build focused toward improving the reliability of our engine, we haven't forgotten about adding some much needed grunt to our beloved EJ25 engine. Follow along with our buildup process as we meticulously assemble the bottom end using key components.
If you recall, a deadly combination of over boosting 30 psi due to a dislodged wastegate line at the track caused a lean air/fuel condition that melted our Cosworth piston, which in turn caused a nightmare of scenarios that ended with a dramatic engine fire. We were able to salvage the cylinder heads, but the block was decidedly thrown in the garbage and replaced with brand-new case halves we purchased from South Coast Subaru located in Costa Mesa, CA.
Prior to assembling the Subaru engine, we sent our JE pistons, rods, crankshaft, and bearings to WPC for treatment prior to assembling the EJ25 engine. What is WPC, you ask? Simply stated, WPC is a metal surface treatment that enhances the surface to reduce friction and strengthen engine parts. WPC is not a coating nor is it shot-peening. The treatment is executed by firing ultrafine particles at the part's surface at very high speeds. The ultrafine media of the WPC process, when projected at high velocity toward the product surface, creates compressive stress (the compressive load per unit area of an original cross-section) at the impact points. At the same time, a micro-thermal reaction takes place. It effectively seals minor surface fractures, allowing a condensed surface to form improving surface density due to the compaction. This altered and highly compact surface condition overcomes the problem of brittleness that is usually encountered when metals are hardened. Treatable metals include steel, aluminum, titanium, copper, and brass as well as soft-surfaced bearings. WPC can basically treat any metallic item in an unassembled state, from rotary apex seals to rear differentials.
Many of the top motorsports manufacturers, such as HKS, Suzuki Sports, TRD, and Tomei Powered, rely on WPC to treat their high-performance products. The WPC process uses a special ceramic bead composition ranging from 20 microns or larger depending on the application and area being treated, which shot-peening can never duplicate. In comparison to shot-peening, the media being used for the WPC process is 50 times smaller and is applied at a higher velocity, pressure, and impact, creating a higher compressive stress level. The numerous impacts during the WPC process not only increase the residual compressive stress but also cause it to reside a lot closer to the surface. The result is a product that looks dull in appearance (as shown in the image to the right), but has durability unrivaled by conventional peening.
Carrillo Pro H-Beam Connecting Rods
The Carrillo Pro H-beam configuration can handle extreme engine loads. The tapered beam allows for some weight saving on the reciprocation end and gives increased clearance for fully boxed pistons. A side-by-side comparison versus a competitor's rod shows why the name is synonymous within the motorsports world and used by top engine builders around the world with good reason. Some key features in design include ribbed PE strap for increased stiffness/minimum PE distortion and stout H-beam rod shaft design.
Notice the Carrillo rod cap with its lipped relief design versus the competitor's piece? The lip was introduced to promote additional strength.
Revco Precision Machining/Balancing
When it came down to matching and balancing our EJ25 engine assembly, we contacted Larry Revis of Revco Precision, located in Long Beach, CA. Revco does everything from polishing, balancing, and knife edging to straightening, strengthening, and machining. They do it all within a reasonable price.
We picked up a brand-new OEM crankshaft from South Coast Subaru. The crank came heat treated from the Subaru factory.
Using a connecting rod balance scale, Revis carefully weighed each rod. This specialized scale is accurate up to 4,000 grams and has the ability to check weight on both big and small ends of the rod. Weighing a connecting rod using this type of scale will determine how much weight to remove and from what side of the rod. A perfectly balanced rod is a key component inside an engine that is spinning 8,000 rpm.
Revco Precision checks for crankshaft straightness, performing a simple technique of stress relieving the metal while straightening out the crankshaft to allowable tolerance. "A lot of guys won't do the stress relief, and they wonder why their crankshafts crack prematurely," Revis says. In performance applications like our EJ205, the crank was balanced to within 0.1 thousandths of a gram. Too often we hear the horror stories of improperly balanced factory and aftermarket crankshafts breaking into pieces and ruining a perfectly good engine.
Revco removed material from our flywheel to balance our assembly before we hauled our parts to be assembled.