So I purchased a used set of RC Engineering 550cc low ohm injectors from a forum member here. They were supposed to fit a miata. Well they don't. They're .160" too short. If I install them they are loose and move around. And the tip where the injector goes into the head is also different. I used an O-ring there.

Sure I could try to get a refund or whatever but honestly I'd rather just make these work. If I remove the plastic spacers that normally space the rail away form the head, it's too tight. But, if I add a .060 washer between the head and rail the spacing is pretty close. Looks like it should work. Is there any reason NOT to do this? With the O-rings on the ends of the injectors they seal by the o ring being crushed between the injector being pushed down and the head where the injector goes in. The 99 injectors tips are different and it appears the injector seals by being in there, not by being forced down. Would that matter?

 

i had a couple washers spacing my rail for a while when i lost one of those spacers, with proper thickness i think you should be fine

 

You will be fine with washers, my RCs fit the same way, I had to use a few washers in place of the spacers.

 

umm did you put the big fat rubber spacer on them?

ie does the bottom (spray side) look like this:

 

FWIW I used a different style O ring, I am not sure if the OEM (Miata) large seal will work, but I never actually tried using it. If you want I could try to find the NAPA part number. FM lists it somewhere on their site too, maybe in the technical section for their dual feed rail, but 2 of the O rings are the same height as the OEM seal, take one away and it fits the RCs shorter pintle cap just fine.

 

Yup, you need the plastic insulator. It keeps the metal body of the injector from touching the metal intake manifold and grounding it (I think).

 

FWIW, those little plastic spacers are actually insulators that keep the fuel from getting too hot. I have been running without the middle one and with washers in its place all summer and have not experienced any problems yet. Starts right up every time. The guy at the dealership said that without that insulator, the fuel may boil and have a hard time with warm starts.

 

Are those insulators dealer only items? Searched on Moss and FM, and couldn't find them. Will the stock ones work, or are they sized to the injector?


Edit: Nevermind. Found 'em at Finishline. http://www.finishlineperformance.com...cat=317&page=2