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Project Subaru EJ205 - Build Log

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Owning a ’03 WRX and a ’05 STI has both its perks and downfalls depending on how you look at it. There’s a great sense of pride when both my cars are running in perfect condition but that spectacular feeling came to an abrupt end during a dyno session a few years back when my ’03 WRX blew a head gasket. After deliberating for a good year after the gasket failure on how to attack the rebuild, I decided rather than fix the problem, I’d fortify the engine using forged internals to improve the engine’s reliability. Follow along as we document the better part of two years, building the long-block. Why so long you ask? It’s simple: Money doesn’t grow on trees.

01 After a bout of overheating issues and coolant purging from the reservoir, a leakdown test revealed our stock EJ205 had seen its last run with a blown head gasket.

02 Upon tearing down the engine and removal of the cylinder heads, it was evident that engine oil was mixing with coolant.

03 It was only a matter of time before the combination of high boost, aftermarket turbo, and stock engine internals would eventually cause the motor to pop. Notice the thick blobs of residue caused from using Dex-cool radiator coolant. Dex-cool antifreeze uses one of two inhibitors: Sebacate and 2-EHA (2-ethylhexanoic acid), which works well with the hard water found in the United States, but is a plasticizer that has been known to cause gaskets to leak.

04 Subaru does not recommend running GM Dex-cool or any OAT-based (Organic Acid Technology) extended-life coolants. The main reason to stay away from these types of coolant is the glopping, or the thick gel-type effect as seen in the photo. Glopping usually occurs when air is in the coolant system and corrosion occurs on the aluminum parts in the engine. Coolant then washes over the corrosion, causing a glopping effect to occur. Using a phosphate and silicate-free coolant is the best solution for most aluminum engines.

05 Analyzing the freshly removed pistons will reveal plenty about the condition of your engine and its health. Heavy scuff marks or scoring on the piston skirts indicates unmixed fuel has washed the oil away from the cylinder walls while a more severe case of scoring can be caused from heat seizing. The case of peppered markings or indentations across the tops of the pistons indicates detonation/pinging, while a melted piston is caused from an excessively lean air/fuel ratio.

06 Howard Watanabe of Technosquare Tuning, located in Torrance, CA, visually inspected the crankshaft along with the rod and main bearings for any unusual wear and/or scoring. We are happy to report that all the parts were within acceptable tolerances.

07 When building any engine, it’s important to refer to the manufacturer’s specification card, along with using the proper tools to take proper measurements.

08 For our build, we used a set of BC (Brian Crower) connecting rods. The BC625+ rods use ARP bolts to deliver the ultimate clamping ability at high horsepower and rpm and is rated in excess of 300 hp per cylinder. Pictured is a comparison of the stock versus BC connecting rod.

09 The stock cast pistons and factory I-beam rods were tossed aside in favor of more boost-friendly components.

10 A micrometer is a measuring instrument that is used to determine the thickness of blocks, depths of slots, and diameters of shaft. Engine builders rely heavily on taking the proper measurements when checking tolerances to ensure the parts are within acceptable specifications.

11 A dial or bore gauge is a very accurate and precise measurement tool that is used to check rod and main bearing clearances as well as piston-to-wall clearances. Every engine builder should own this tool

12 For the connecting rods, we used a set of ACL bearings with Calico’s CT-1 dry film lubricating coating. CT-1 coated engine bearings have greatly extended service life over uncoated bearings. Engine builders have also seen reduced damage in engines from heat- and lubrication-related failures

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