Threaded holes in back of block

[ctaylor738]

In a major step forward, I have the 280's engine off the stand.  The transmission has been re-sealed and is ready to go on. 

But I noticed two threaded holes on the right rear back of the block that look like they should have plugs in them see picture). There are cut-outs in the engine plate for them.   I can't find anything in the BBB or Haynes, though.  The EPC does show 3 plugs but on the side of the block.

Can anyone shed some light on this?

TIA.

[ja17]

These are for oil gallery plugs and they must be installed!  Check the ones in the front also.

[ctaylor738]

OK.  Thanks for averting a major disaster.  I can just see it now - no oil pressure and oil gushing out the back of the engine!

I am not seeing anything in the front of the engine.  Where would those holes be?

UPDATE - Found it.  There is one plug (missing) in the chain galley.  You can see it (or the hole) at about 7 o'clock if you remove the large cover that holds the distributor shaft.  It is accessed through the hole that is covered by the plug holding the timing pointer.

After some more research, I believe the PN's as follows:

Chain galley (1) N000906 010000 EPC figure #143
Rear of block (2) A000 990 47 12 EPC #137 (shown at front of engine!)

[Benz Dr.]

The holes at the front of the block stop at the edge of the chain case. One of the holes has the oil prerssure relief valve and the other has a plug similar to the ones used at the back of the block.
 Use a bore brush to make sure there isn't anything hiding in the oil galleys. Even a few pieces of grit can cause a lot of bearing wear and scratching. Blow through the galleys with compressed air after you use the brush. All of this should be done before you start assemby.

[ctaylor738]

Well, it turns out that there is more to this story.

There are actually four plugs.  Two in the back, A000 990 47 12, two in the front (A000 990 47 12 and N000906 010000).   WRT to the front, the smaller plug is installed at about 9 o'clock in the block in the round opening covered by the distributor housing, where the sprocket for the auxiliary shaft sits (see picture).  The larger one goes, as described earlier, to the right of the pressure relief valve.  This larger plug, according to Mike Elias at Metric Motors is "optional" but they recommend installing it.  This is probably why it's not shown in the EPC.

The small plug behind the sprocket is easy to miss and if not installed results in no oil pressure.  You can probably figure out how I discovered this.