I have an '86 GXL with a bad engine and am installing a running S5 engine in the car. I plan on using the S5 intake manifold as well, but was curious about the injectors.

I assume that I'll have to use the S4 injectors since I am keeping the original ECU and wiring harness and the S5 injectors are different impedance (S4 = low, S5 = high IIRC). My main questions are 1) will the S4 injectors fit properly in the S5 manifold? and 2) can I use the S5 fuel rails or do I need to use the S4 ones?

Thanks for the help.

 

Injector size and shape is identical. '86 to '87.5 used low impedance injectors, so you're right in that you'll need to reuse the S4s. Also, be sure to keep the S5 diffusers in the intake manifold. They're different heights than the S4 versions, and if mixed up will lead to the injectors not seating properly in the rails (especially the secondaries).

 

Thanks for the help. After I posted this thread, I did see where the injector shape was the same, but I'm glad you confirmed it.