Tired Old Engine

The old engine in my Datsun 240z at the last track day started to feel underpowered like there was more for the engine to give. Shortly after the motor began smoking on take off so it was time to do a compression check.

The Results:

  • Cylinder #1 140psi dry / 185 wet
  • Cylinder #2 140psi dry / 182 wet
  • Cylinder #3 133psi dry / 170 wet
  • Cylinder #4 140psi dry / 165 wet
  • Cylinder #5 135psi dry / 160 wet
  • Cylinder #6 135psi dry / 175 wet

The low dry numbers combined with higher wet numbers indicated that there was an issue possibly with the piston rings. Next was a leak down test and that confirmed that there was wear on the rings and it was time for a rebuild. Before for the rebuild however it was time to get a baseline dyno chart.

Thanks to Rob at ZCarGarage for the help. Looking at the dyno chart you can see the L28 is under powered and also a little low on torque. Max power of 110 hp and 141 ft-lbs of torque isn't the greatest performance motor. The Datsun deserves a better motor.

The engine is old and tired, so it was time to build something more powerful. As I still wanted to drive the car, I decided to source another block and head for building a new motor. Then I could swap over the new motor into the car when finished. A perfect opportunity for learning more about building performance engines, even if a single overhead cam is old technology.

The next article in the engine build series we start by disassembling the cylinder head in preparations for modifications and machining.

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