Injector O-rings?

[mrbozo]

I presently have my injectors out and have noticed that they have different O-rings under sealing them to the manifold.Some have two rubber o-rings and some have 1 o-ring and a spacer under it.Which way is correct? They are rc injectors and not stock.

 

[HUNTJAMES]

There are little rubber o-rings (looks like a rubber flat washer about 1/8" thick) that are supposed to go around the injector nozzle and those should be replaced with new ones when you change the injectors, new o-rings on the fuel rail side is a good idea, use assembly lube or something from your night stand to make them slide in without cutting the o-ring on the fuel rail.

Any questions or new o-rings call:

RC Engineering Inc.
(310) 320-2277
20807 Higgins Court
Torrance‎ CA‎ 90501

 

[angus]

I think what you mean is some of your injectors are using a phenolic spacer and a rubber o-ring at the base (inthe intake manifold) and some are using doubled up o-rings?

The car originally has just one thin o-ring, but aftermarket injectors can vary so I would say use whatever yo need to make them fit, if you think that double o-rings are the way to go, keep in mind that there are also thicker o-rings available, 90-93 integra has the thicker ones.

A bad fit here will cause a vacuum leak.

 

[ScienceofSpeed]

For RC injectors for 1991-94 with out the air injection system, remove the plastic spacers in the factory manifold and replace only the rubber o-rings. Retainer the plastic spacer between the fuel rail and the intake manifold. Do not use the aluminum spacers that RC sometimes includes, they are not for the NSX. For 1995-2005 with the air injection system, the setup depends on injector model number - we supply the correct o-rings and spacers depending on the year.

regards,
-- Chris

 

[NSX-Files]

For RC injectors for 1991-94 with out the air injection system, remove the plastic spacers in the factory manifold and replace only the rubber o-rings. Retainer the plastic spacer between the fuel rail and the intake manifold. Do not use the aluminum spacers that RC sometimes includes, they are not for the NSX.
regards,
-- Chris

Chris,
I have RC PL9-550 injectors I'm planning to install in my stock 1991 intake manifold. My RC injectors currently have the double regular-style o-rings on the base. Like these:

Do I remove both the OEM "seal ring" (part #2 on the parts diagram) and "injector insulator" (part #4 on the parts diagram) from the manifold and just use the double o-rings? Or do I use the OEM rubber seal ring on the RCs? Or something different?

Seal ring:

Insulator:

Last 2 images courtesy of DanOLand.com - Awesome website!

Is the OEM upper o-ring (#17) on the fuel rail side the same size as what the RC injectors should use? (7.3 X 2.2 is what the parts diagram says, I assume that's millimeters).

Are these (#7 on the parts diagram) the plastic spacers you refer to between the fuel rail and the intake manifold to retain? (the two black ones on the studs between the three injector holes where the fuel rail mounts)

TIA!

 

[ScienceofSpeed]

For the 1991-94 with stock manifold, use only the factory o-ring at the base of the injectors, the small o-rings in your photos are not used with the 1991-94 stock manifold. Yes, leave the spacer between the rail and the intake manifold.

-- Chris

 

[NSX-Files]

For the 1991-94 with stock manifold, use only the factory o-ring at the base of the injectors, the small o-rings in your photos are not used with the 1991-94 stock manifold. Yes, leave the spacer between the rail and the intake manifold.

-- Chris

Thanks, Chris! So to be clear, for RC injectors on a 91 manifold, remove the hard plastic "injector insulators" (part #4 on the parts diagram) from the manifold and don't use them. Just use the OEM square shaped o-rings ("seal rings" - part #2 on the parts diagram) at the base of the injectors.

 

[NSX-Files]

I tried installing my RC PL9-550 injectors in my 1991 NSX today and it's obvious it ain't gonna work with what I have.

Based on SOS Chris' instructions in this thread, I bought new oem seals (the large square o-rings) for the injector bases, and new small o-rings for the top of the injectors where they go into the fuel rail. I've kept the bobbin-shaped rubber cushion rings at the top of the injectors (between the top o-ring and where the electrical connector is). I also removed the phenolic plastic spacers from the manifold. Finally, I retained the plastic spacers between the fuel rail and the manifold mounting bolts.

With this combination, I can tell the injectors are not going to seal in the manifold. The RCs will not go into the manifold with the oem square o-rings because the diameter of the square o-ring on the injector is too fat. Also, even if they would go in, the RCs are slightly shorter than oem injectors, so I think the plastic spacers between the manifold mounting bolts and fuel rails might keep the rail from going down far enough onto the injectors. I'm not sure this is a deal breaker. First I have to solve the bottom part of the injector.

I'm totally stuck until I figure this out. I know plenty of people have put in RC 550 injectors in their 91s, so there must be a right way. Any help would be greatly appreciated.

 

[chudson1549]

David I should have my injectors back today. I'll mock mine up tonight. If I remember right. fuel rail to manifold.

Rail -#17 (on RC inj) -#3- injector - #2 -#4 - manifold..
BTW Mine did not have the double o-ring at the base. Mine have a solid rubber ones like here

I need to make sure..
Keep the spacers on the studs (red arrows)