I've been trying to research this, but can't seem to find any info. I just got some used RC 550cc injectors, and before I install them I did some research where some people said they needed intake spacers. Something about fuel rails hitting the lower plenum. Does anyone know what spacer to look for? Or if I need them at all?

 

I have those same injectors. All you need is to use washers as spacers on the fuel rails. The RC injectors are a little larger than stock, so you need to use the washers underneath the rails at the mounting points.

Also I never had any issues with the rails touching my lower plenum.

 

The injectors should come with 10mm machined spacers for the fuel rail. If not, we have them in stock and RC probably does as well. You also need the pigtail connectors as well, or the Denso to RC adaptors as the RC uses a typical domestic connector instead of the Denso connector on the OEM harness.

 

I have the RC 550's as well. I used the incleded fuel rail spacers and also had to use a lower plenum spacer to clear the injector tops with the lower plenum. Motordyne sells them, might as well get the iso thermal gasket too

 

Do you only need the plenum spacer for only the stock rails? What about the aftermarket rails?

 

What did you guys do about o-rings (rings that go into the lower manifold). Are they the same size as the stock injectors?