Three reasons why your Subaru engine might fail you

How to go racing with your Subaru not worrying that you will need a lift home from some stranger with a car trailer? You have to consider that there are 3 main reasons why your Subaru engine with increased power might fail you:


We had the same problems with our Subaru many years ago when we started looking for some help to prevent the same problems mentioned before. But there was no one who could give us some convincing solutions. This led us to find it by ourselves – and you know what? Not only that we found the solutions, but we also tested and boosted our experience by maintaining more than 300 engine blocks that have improved projects in Europa.

Why are your cylinder walls cracking, and your head gasket is leaking? The answer is – cylinder walls are not supported enough.   

For open decks, there are only two supporting tabs for each cylinder or four supporting tabs for semi-closed decks. If you push your engine hard, cylinder walls are going to move under high cylinder pressures. To prevent it you need to support the cylinder walls and it is commonly called CLOSED DECKING.

Closed decking is a process where the top plane of the engine case is machined so that it can accept CNC machined inserts. After this process, cylinder walls are completely supported in the weakest place – at the top, where combustion happens, and proper support is needed when BANG happens. All the coolant bores that exist in the head gasket are machined in-cylinder supporting inserts, so engine cooling is not affected. An extra cooling passage is machined for stages 2 and 3 so the engine coolant flows freely under the head gasket.

We provide closed decking for all EJ engine series in three stages and other manufacturer engines. Learn more here. 

Why are your engine bearings failing?

EJ engines are often considered to have weak main bearings that lead them to oil pressure problems and both main and rod bearing failure. The truth is that bearings themselves are as good as any other engine manufacturers would have. If you own a Subaru EJ block, then there is almost a 100% chance that the main bearing bore alignment is out of line. To correct it we do vertical CNC line boring.

  1. 1.We start by removing as little material as possible from each of the case halves depending on how much the bores are out of alignment from each other;
  2. 2.Then we bolt the cases together;
  3. 3.And after that, we align the case very precisely against the CNC spindle axis after which the line boring process within a precision of 5 microns are made

This prevents bearing from failing caused by incorrect clearances. To keep these clearances stable under high loads next step is mains pinning.

High boost and high cylinder pressure applications cause distortion and flex in Subaru EJ series engine cases which shortens bearing life. Machining pins to the Subaru case main webs reduce distortion and flex caused by both situations. Mains pinning is done before case assembly for line boring, so newly straightened cases are ready to go for final assembly after machining is done.

These are the solutions we have found and tested. Now you know how to make really Hard Core for your engine: closed deck + line bore + mains pinning is a MUST. It will keep you away from troubles and save some time and nerves.

Stay safe & respect your engine!