Fuel Injector to Head Sealing - Double O-ring
 

I think I have a vaccuum leak at injector 4. I hear some intermitten hissing.

Flying Miata suggests using two Ford O-rings or one Mazda Injector Seat.

http://www.flyinmiata.com/support/in.../Fuel_Rail.pdf

Anyone know the size for the Flying Miata Double Ford O-ring?

Or should I just go buy the OEM Seats?

I don't know the size, but they are pretty standard. Take an injector (an old one, if you need to use the car) down to the local HW store. Find the place where they have the rings, and try them out. Just fit them on until you find the size you need.

are you sure it's not user error? installed correctly there should be no leaks

I noticed it after changing the CAS seal. I may have bumped it a few times. I'm not sure.

I was planning to do the DIY dual feed, and wanted to replace all the seals at the same time, just in case.

Looks like you have an extra car so best thing to do would be to send them to injector rehab
https://www.miataturbo.net/forum/showthread.php?t=17640

at minimum, they have a seal kit.

Sounds good. Will they "rehab" the RC550s?

yes

I went to NAPA and had them look up various Fords until I got the right injector O-ring that FM was talking about. I can't remember what engine it was exactly though. I doubled them up with stock injectors and it fit like a glove, when I went to RCs I could still use them, just 1 per injector not two.

How did you tell it was the right one? Just compared it to the insulator?

In a pinch you could also use properly cut pieces of silicone hose. I'm not sure of the size though.

The Ford parts are probably from a Mazda engine as well, most likely a Probe or an Escort GT.

I knew roughly what size it had to be, ended up being right the first time.

It was either the Mazda/Ford 2.5L V6 (93+ Probe GT/ MX6 LS), 4.6 Ford, or 5.0 Ford.

Hey Guys

For the RC Injectors, do I need that grommet that goes behind the O-ring on the fuel rail side?

I'm going to just order all new seals from the dealers, just wondering if I need that. I don't see it on my car currently, but it may be inside the fuel rail.