If two middle cylinders of a V-8 engine show low compression readings of 50 PSI while others read between 135 and 140 PSI, what is the likely cause?

When two middle cylinders of a V-8 engine exhibit low compression readings compared to the others, it often indicates an issue that affects those specific cylinders more directly than others. A blown head gasket is a likely cause in this scenario because it is known for enabling compression loss between adjacent cylinders. In a V-8 engine, if the head gasket fails between the middle cylinders, it would lead to lower compression readings for those cylinders while potentially allowing the adjacent cylinders to maintain higher pressure levels.

The location of the compression loss correlating with the center of the engine suggests that the head gasket could be leaking combustion gases or allowing coolant to enter the cylinders, thus lowering the effective compression. It’s important to note that while other issues like faulty piston rings or leaking valves could potentially affect compression, they would more likely result in lower readings across multiple cylinders rather than isolating to just the two middle ones. Clogged fuel injectors would primarily affect fuel delivery and would not directly lead to low compression readings. Hence, the assessment points towards a head gasket issue as the most likely cause.