Boxer Engine Rebuilds

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S&J Boxer Engines

We have been rebuilding and developing Subaru EJ20 engines since 1998, by 2000 we had begun stroking and using oversized pistons/sleeves, and then in 2003 with the ease of access of the EJ25 we found ourselves building and race prepping many different combinations of the famed 2.5L Subaru Boxer engine.

Many people may say an "engine is an engine", but the flat four turbo Subie motor certainly holds a great number of "tricks and traps", some of which we have had to learn the hard way, and others that we have picked up by being partnered with the likes of MRT Performance in Sydney, our resources and testing grounds have been almost limitless.

Most importantly when investing in something as large as an engine replacement or rebuild, it is extremely important to make the right choices of internal components and services to suit your needs. It would be easy to be miss-advised and waste money in one area and overlook something more important that would match the desired outcome of the project. For example money is often more wisely spent doing mild port work/matching to the cylinder heads than replacing the con-rods with stronger ones, the reason for this is that by increasing flow throughout the heads, power is made easier and pumping losses are reduced on the exhaust stroke, therefore con-rods and bearings are far less venerable to fatigue and stress breakdown!

"Blue-printing" of an engine is sometimes a term that is used a bit loosely, but the following points will briefly explain some of the areas that we "Blue-print" during an EJ build!

  • Blue-printing Crankshaft, a labour intensive process that is carried out during the early stages of machining. Here we are eliminating "nominal" sizes (which means they have a + or " tolerance). The engine block which supports the crankshaft at its main journals is closed up to correct tensions without the crankshaft, the tunnel is then checked for trueness, taper and ovality, if any defects are found within 0.00025" they are rectified by a tunnel boring process. Following the trueness of the engine block, the new "race series" main bearings are installed, the block is re-tensioned again without the crankshaft, then each bearing internal size is measured and recorded. Now the 5 crankshaft main journals can be ground and linished precisely to achieve the exact clearance that we are after, all 3 of the + or " tolerances are now removed. This process is extremely critical for any high performance or track application.
     
  • Blue-printing Con-Rod to Crankshaft, just like the 5 main bearing journals on the crankshaft the 4 con-rod bearing journals go through a similar process. In this procedure the con-rods are tunnel bored to an exact size, then fitted with the new "race series" bearings, re-tensioned, measured and recorded, and then the crankshaft is ground and linished precisely to an exact clearance for each con-rod bearing. Con-rod bearing failures are extremely prevalent for the Turbo Subaru engine, and it is our belief that the nominal clearance processes during the mass production often leads to the short life of these bearings, once again for high performance or race applications, this is another critical step in the building of an EJ engine.
     
  • Piston-Bore clearances, as with any engine build the machinist will aim for a specific piston to bore clearance, we take it a step further and finalise the boring process with a "torque plate" fitted to each block half. A torque plate is a billet of alloy that is the same thickness and density as the cylinder head for that model, this plate has 2 large holes machined into it to allow the boring equipment to pass through. The torque plate is bolted to the block half in the same manner at the same tensions as the cylinder head would be, this distorts the cylinder walls exactly as they would be when the engine is assembled, so once again precision takes the place of tolerance (+ or -). This process is used for gains in power as well as reliability, as is the final finish "Plateau Hone" that we use in the cylinder bores, this is Nascar technology from the US, which is only available from limited engine shops.
     
  • Cylinder Head Porting, all standard EJ cylinder heads have one exhaust port on each side of the motor that flows 15-20% less than the port for the cylinder next door, the flow matching of these ports is just one area where power and reliability can be gained from a "port job". Many hours on the flow bench have proven worthy for both inlet and exhaust port flow improvements, and an extreme amount of data has been recorded for each model with each capacity and level of mods. As with any port, the short radiuses, diameters and finish are crucial to a worthy outcome. Camshafts, valves and springs are a consideration at the time of the cylinder head re-work, again good advice and correct choices are paramount here. Also port matching to intake and exhaust manifolds is not to be overlooked at this time, we can't stress enough how important flow is to power, torque and reliability!
     
  • Camshaft Dialing In, it is a fact that even standard camshafts in a standard engine can be up to 6 degrees from their ideal rotating relationship with the crankshaft, when you factor into account that a Turbo Subaru engine has 4 camshafts that is a lot of give or take tolerance. Many people also don't realise that the machining of heads and block halves plus the altering of head gasket thickness has a major influence on the precision of camshaft timing, and in turn relationship between the valves and pistons. The addition of aftermarket camshafts, will also further the need for a precise Dial-in of all 4 camshafts to the crankshaft. We have seen gains of over 20kw ATW from simply removing an engine and Dialing-in the cams correctly. As you can see, this is another worthy process to carry out during any high performance street or track engine build.

With all of the above in mind and the correct choice of hardware and tuning 300kw at the wheels is not a difficult target to achieve, but "horses for courses" as always, so if the time comes for a rebuild of your EJ we can help advise you on the package that will suit your needs.

We are extremely passionate about our engine builds, our attention to detail does not stop on the inside, every engine is detailed to a degree that matches its application and the appearance the client is after, have a look below at some of the engine bays that we have worked in recently!

 

Please Feel Free to inquire about any level of EJ engine build, and we will see that you get the right advice!