I have seen some people running their Subarus without any timing covers, front or back plastic. Isn't that trouble waiting to happen.

I wouldn't do it on an 2.5 motor ... but on a non interference 2.2 , other than losing a finger .... nothing much would happen. Some offroader's  say it keeps snow and mud from building up under the plastic. 

Once you delve into the engine work, it becomes a matter of personal preference.

In this case, I am one of those that feel it's there for a reason, so I keep mine on.

 

O.

Good covers and no leaks keep things nice and clean and rust free.

My CA based 96 Legacy has not had front timing covers since I replaced the long-block several years ago.   It's true the timing belt and the pulley surfaces get a little grubby.  But the probability of a negative consequence is lower given the posh street life the car enjoys (no gravel, mud, snow, hard driving and low chance of bad rust).   I gave up on the covers after a rough roundy-round with the crankshaft pulley keyway and a more recent head gasket debacle.

 

I wouldn't recommend running without covers for most users.  But if you are at the point of taking your engine apart anyway, then it is a personal choice.   My choice is based on the fact it is more likely I have to take something apart anyway before I encounter a problem caused by a missing belt cover on my $1000 KBB-value Subaru!

I run both of my old 2.2s without them. No chance of bent valves on the pre-96 2.2.

But I also keep a full timing kit of used timing pulleys and an old belt in the trunk. Takes me less than 45 minutes to do a timing belt and pulley change.

 

On an interference motor I would keep the covers on.