Hi Noel,

Datsun made several totally different 1500cc engines, including but not limited to E15, J15, A15.

Which one do you have?

120 lbs sounds good, especially if they all four cylinders read the same.

Most engines I've worked on have around 145 psi, it all depends on the cam -- as well as the static compression ration. Most engines from 70s and 80s used 8:5:1 ratio. Most Datsun engines were around 9:1.