• After a crankshaft pulley vibrated loose, it became necessary to rebuild at least the bottom half of the engine

  • Deciding that I should take this seriously and replace everything I could, I opted for a full engine rebuild (everything but new pistons and rings) while I had the engine out

  • Took two weeks to rebuild, replace and generally refresh the engine. When re-installed in the car it started on the first roll


The rebuilt BP4E engine hanging on the crane before being put back into the Miata


In the process of engine removal I went through a number of procedures to make reassembling easier:

  • Color coding all fasteners. This both helped identify what size it was and weather it had been disassembled already or not. Through this process I learned that Mazda uses only 4 main fastener sizes.
  • Laying out the disassembled parts in a grid indicating where they came from (i.e. all valves laid out exactly how they came so that none of them would have to be re-seated.

While this was a first attempt at serious engine work, overall I consider it quite a large success, not in the least since the engine started on the first try when put back into the car. A feat I have been sometimes unable to replicate with smaller and far less complex repairs.

The following changes were made to the engine while I had it removed from the car:

  • New oil and water pumps
  • All new seals and gaskets from intake to exhaust, including head gasket and valve seals
  • Recovering exhaust header
  • New harmonic balancer
  • New crankshaft
  • New main and thrust bearings
  • New timing belt and associated bearings
  • Off-engine oil filter for ease of access
  • New oil temperature sender and gauge
  • New shifter boot and oils
  • Entirely new fluids in entire driveline
  • Cleaned and serviced all parts of engine
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