I
wanted to improve the performance of my '77 280Z without resorting to
using SU carbs. I had already installed a fresh stock engine and a
header and decided to work on the intake as the SU carb'd cars using
this same type engine seem to run stronger than the FI cars do.
I started with a non-EGR '75 intake as the center plenum looks larger to me. Plus I like the way they look and I didn't plan on using the EGR anyway. I then found an old weber "big throat" throttle housing which is much larger than the original, might be able to source one off ebay? Next I spent a few hours doing some serious enlarging to the throttle housing end of the manifold and also ground off the external bosses that I no longer needed since I planed to do away with the cold start injector and the idle air regulator etc. Below are some small snaps shots of the finished manifold with an 82 turbo 280 fuel rail (these didn't use a cold start injector). The left shot shows a stock 81 ZX intake vs modified 75 Z one.
I also "robbed" the injectors and injector connectors from a 300zx I found in the junkyard that had just had the injector campain done. This is a great way to get a like new set of real nissan injectors for your Z and they are a direct replacement. At this time I'm still using the factory air box and air flow meter.
The results? A noticable improvement. Before the engine started falling off around 4500 RPM and was basically done at 5000. Now it pulls much harder at 3000+ and pulls all the way up to 6000. It will probably run much closer to an SU carb'd car now with none of the hassles those old carb setups have.
The next project I'm going to work on is replacing the factory air flow meter with a larger one (see pictures above) I found on an old BMW 530i that has the same type electronics. It's a 3 inch bore version, will have to swap out the electronic board with the NA Z one and am going to fab up 3 inch plumbing to move it in front of the radiator support and supply it with a K&N cone filter. I'll post the results of that swap and some pictures when that's done.
I started with a non-EGR '75 intake as the center plenum looks larger to me. Plus I like the way they look and I didn't plan on using the EGR anyway. I then found an old weber "big throat" throttle housing which is much larger than the original, might be able to source one off ebay? Next I spent a few hours doing some serious enlarging to the throttle housing end of the manifold and also ground off the external bosses that I no longer needed since I planed to do away with the cold start injector and the idle air regulator etc. Below are some small snaps shots of the finished manifold with an 82 turbo 280 fuel rail (these didn't use a cold start injector). The left shot shows a stock 81 ZX intake vs modified 75 Z one.
I also "robbed" the injectors and injector connectors from a 300zx I found in the junkyard that had just had the injector campain done. This is a great way to get a like new set of real nissan injectors for your Z and they are a direct replacement. At this time I'm still using the factory air box and air flow meter.
The results? A noticable improvement. Before the engine started falling off around 4500 RPM and was basically done at 5000. Now it pulls much harder at 3000+ and pulls all the way up to 6000. It will probably run much closer to an SU carb'd car now with none of the hassles those old carb setups have.
The next project I'm going to work on is replacing the factory air flow meter with a larger one (see pictures above) I found on an old BMW 530i that has the same type electronics. It's a 3 inch bore version, will have to swap out the electronic board with the NA Z one and am going to fab up 3 inch plumbing to move it in front of the radiator support and supply it with a K&N cone filter. I'll post the results of that swap and some pictures when that's done.