The 1275 donor unit was purchased complete minus the original cylinder head that was removed by the previous owner to replace a head on another 1275 unit. In this state this engine was perfect for this conversion and at its price it was a bargain.
The unit was immediately stripped down to find that the engine internals were is excellent mechanical condition and just looked like it required a little cosmetic clean up. I was unaware of the milage of this engine so this was a pleasant surprise. The engine was stripped and visually inspected to component form to undergo its re-working and machining.
Im not a fan of red engines and the previous owner has decided to paint over old engine oil, and dirt and it looked terrible. This was removed on the the block clean up, the block was degreased and then the block repainted with 3 coats of high temperature paint.
The picture above also shows the cylinder block face modifications (plugging) complete ready to now go away to the machine shop and be rebored to +060″ oversize taking engine capacity to 1330. The engine will also have new cam bearings fitted and the block face skimmed to confirm flatness. All plugs were drilled and tapped in metric sizes and then mild steel inserts fitted, sealed and locked into place while the sealer went off. Make sure you check that the thread-lock / sealer you are going to use is suitable and seals even at high temperatures. You do not want leaks anywhere around here once this is put back together.
Note: The 3 front original “A series” 5/8 UNC stud holes are left as they match the BMW K100 head in their original positions. The block face will then be re-drilled following the specialist components template to match the “A series” block to the 10 head stud pattern of the BMW cylinder head. The A series rocker feed oil gallery hole remains in its original place in the block. The BMW head oil feed drilling will be welded and re-drilled on an angle to match and supply oil to the head. If you do not want to do this there is another option. This hole would also be plugged in block and head and an external oil feed can be run. The block will have to have an external drilling into an oil gallery and then tap a line into the m8 oil gallery test port location on the new head. If your going this far you may also considering the “dry deck” setup.
Tapping shown below and then block repainted below that.
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