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Subaru EJ Motors - Preventing spun bearings

General Engine Building Discussion

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Subaru EJ motors have a common failure - in stock or modified engines, that is a spun bearing, typically it is a rod bearing.

Thinking aloud, the normal cause for a spun bearing is lack of oil. Whether it be from no oil in the sump, pickup being starved or some other reason as to why oil was not circulating through the system.

Debris and lack of oil changes can also cause this I believe, as the contaminated oil circulates wearing out the bearings, causing larger clearance's reducing oil pressure.

Tuning is also another factor, along with poorly built engine clearance's to begin with - but I want to discuss particularly the EJ oiling system in general.

Now - there are lots of reports of people having maintained there oil changes and having had oil in the engine - yet these motors are still spinning a bearing.

Have noticed a thread on nasioc where some people are porting/smoothing out the oil galley's to help prevent this - is there any truth to this?

Do any subaru engine builders port/smooth out any oil passages/galley's?

The two biggest issues with the Subaru engines in my opinion is that even in 100% stock form they use too much timing and are constantly relying on the knock control strategy. This puts unnecessary load on the bearing shells which is made worse by the small size of the bearings in the first place. The other issue that plagues these engines is oil starvation due to high lateral g forces during cornering. It's very common on a race track but can even be an issue on the road with a modified car with good suspension and tyres.

Smoothing the oil galleries is a common modification that can improve oil supply but that on its own is not enough for these engines in my opinion.

Breather system is also mega important in a boxer. The killer b ball valve look interesting.

@Daniel, that is an interesting product idea. I just had to google it. good find! Unfortunately the FA20 we're dealing with these days doesn't use breathers from the rocker covers however I have considered adding them.