You would notice a fuel leak if there was one. The clips themselves don't provide any sealing themselves...

 

+1 here for using them. They stabilize the injectors to the rail. Install the injectors onto the clips and then drop the whole assembly into the ports guiding them in as you go along. Don't attempt putting the injectors into the ports and then seating the clips on after the fact. The former assures the injectors are stabilized between the rail and the ports. The latter just tears the clips up and they don't seat properly. Assuring there are no leaks is paramount. You don't want an engine fire, yes? Use new O-rings w a light coating of dialectric grease or similar to seat the injectors to the ports.

The fuel rail/injectors have nothing to do with vacuum. The only vacuum related item is the hose connecting the regulator to the intake manifold.

 

They're just there to make it easier to install/remove the fuel rails while keeping the injectors intact. How many people here running upgraded injectors are using the clips? Even with the clips installed, you can still rotate the injectors freely when everything is put together and tightened down. They serve no purpose other than convenience.

 

I reinstalled the rail without the clips.. All is well

 

I have after-market SLP fuel injectors and the clips will NOT fit on these so I'm leaving them off. I used Vaseline to coat the new o-rings after cleaning the injectors out with carburetor spray.

 

As long as the injectors will not physically drop down out of the fuel rail, you're fine. The stock ones will bottom out on the intake manifold, but the newer thin style ones used on LS engines will fall right out and cause a fire if you don't take measures to keep them in place.

 

The SLP's I have been running in there for at least 10 years are thinner than ACDelco stockers, but they definitely aren't much "newer". There is a support clip (c-clip) at the bottom of the injectors to prevent them from going too far down into the port. They have never leaked to this point. I have interest in this topic again because I just replaced the O-rings while I had the fuel rail unit out for a new fuel injector regulator. The compression of the 4 bolts that tighten down the fuel rails keeps the injectors firmly planted with no potential for vertical or lateral movement. If there was a leak it would be due to an O-ring being torn or compromised. I'm keeping the valve covers off for awhile so I can continue to monitor the fuel injectors for any leaks with the new O-rings now in there. I also installed a Dorman nylon fuel line coupler and connector on the 3/8" sending line from the tank because there WAS a leak in the stock metal connector due to the torn-in-half orange O-ring inside. The nylon pieces look rather chinsy, but the ratings and most all of the reviews reported good results. So now I'm always sniffing around the rear and front of the car whenever I finish driving. Safety first!

 

I run the 30lb Ford injectors. I put them in about 10 years ago with no clips and they have never leaked.

 

If BK is still around...he can comment on how his car name became "flambe"

gotta ALWAYS make sure there are no fuel leaks anywhere, especially the engine

 

gotta ALWAYS make sure there are no fuel leaks anywhere, especially the engine

+1
It was a blessing in disguise that I decided to change out the fuel pump (again!) when the recent no-start issue occurred. That's when I discovered the dripping 3/8" fuel connector on the sending unit dripping fuel. No bueno! Immediate r/r performed, but this time with a Dorman nylon connector and nylon coupler to make the line about 3" longer. I did not go with the same metal connector as a replacement because I do not want the same thing to happen again. Thought I'd try the nylon for a change and monitor periodically for leaks. I found that the line was unnecessarily stretched to the limit when removing the metal connector. The Dorman nylon connector comes with about 18" of 3/8" nylon fuel line attached to it so it was easy to make the line a little longer with some play, which required the nylon coupler. Holding up well so far. Easier to install the gas tank with the added length to the fuel line.