They are not engineered well; they are not a machined part or built in a proper fixture that ensures correct fitment. They are secured with a thin tab that easily bends. They are pipes that are welded together that are not even square with the manifold at each injector. If you look down at each injector they do not sit center of each injector hole in the manifold. I am amazed they seal at all. With the injectors all at slight angles they are not pushing straight down on the seals in the lower manifold. With new seals they seem to work, but I would be surprised if they seal well over time with how crude they are built. I could go on, but I think you get the point. I prefer side feeds for many reasons…… The 300 degree rail is a CNC machined part with perfect fitment. They are completely thermally isolated from the upper and lower plenums. On side feeds new fuel is constantly going around the injectors cooling the injector coils, where the top feed cans heat soak. Something to keep in mind is the 300zx was Nissan’s baby and they overbuilt everything and choose the best components available. Side feeds are more expensive and I believe Nissan choose them because they are better as they were not concerned with cost when building these cars. Nissan wanted a supercar and 300ZX was born. Nissan /Datsun started making fuel injected Z cars in 1975 and those first cars had top feed injectors……They continued to use top feed from 1975 all the way through 1989 with the 280Z, 280ZX, and Z31 300zx. They went to side feed with the Z32 because it was there super car and they wanted the best! The Stock injectors were awesome and the early style only had failures because the fuel was later changed. The Ethanol eats away the protective coating is what kills the early style injectors, they simply are not compatible with today’s fuel. The late style side feeds are designed to work with ethanol and failures are almost non-existent.
