MG Car Repair: midget 1275cc, oil filler cap, combustion gases

Question
Since getting my 1275midget when y piece from twincarbs connected to front timing cover it pulls oil up from the sump??? Engin new pistons ant rebord new shells more carbs but still doing it??? Also i tsken timing cover off and replaced the mesh. If i just connect twin carbs with one pipe it runs ok? But i want it proper please can you help????clive

Answer
Hi Clive.  When an engine is re-bored and has new pistons it takes a while for the new piston rings to bed in to the shiny new bores.  During this time there is "blow-by" and the crankcase pressurizes with stale combustion gases.  Your carbs are doing a good job sucking all these gases out of the crankcase and burning them in the engine.  

As a temporary measure you can reduce the effect by putting a wooden dowel into the rubber pipe by the Y-piece and drilling a 3mm hole in it, so it can still suck but not so much.  After your new engine has done 3,000 miles it should be fully bedded-in and you can remove the dowel.

By the way, have you ever removed the oil filler cap to clean the mesh inside it?  If not, the cap could be blocked with old black deposits.  Take it off, wash it in a jamjar half full of petrol and then allow it to drain and dry.  This could make a difference.