EFI install?

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CoolCat33

Member
Joined
Jan 29, 2017
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Location
Illinois
My Car
1971 Mach 1
302 Automatic
I’m looking at going with the Holley Sniper efi kit. Everything seems pretty easy and straight forward except how and where to run a return line. It appears that there is a vapor/breather line that runs from the tank up to the engine bay. Can you use this as a return and then use a vented cap?  Or do I need to drop the tank, drain the fuel, then drill a hole to install a fitting?

 
I have not done this upgrade myself yet, but others have,

1) Yes, there is a rigid vapor return line that runs from the firewall down the tunnell to to top of the tank.  

2) The top of the tank also has a bung ring type fitting that I thought I had heard that the existing tank hole can take a drop in electric fuel pump that will work with the EFI systems.

Here you go!



kcmash

 
Page 5 of the Sniper manual 199R11031 clearly states:

DANGER! Do not use the vapor canister lines as a fuel return line. Possible fuel leaks may create a fire or explosion hazard,

causing serious injury or death.

 
Last edited by a moderator:
I have not done this upgrade myself yet, but others have,

1) Yes, there is a rigid vapor return line that runs from the firewall down the tunnell to to top of the tank.  

2) The top of the tank also has a bung ring type fitting that I thought I had heard that the existing tank hole can take a drop in electric fuel pump that will work with the EFI systems.

Here you go!

Thanks for sharing this. I am wanting to do one of these Holley Sniper EFI setups as well and have been trying to figure out the fuel system. I was planning on getting one of the Holley in tank returnless retrofit pumps. And this video pretty much answered my questions about how to mount it perfectly. 

https://www.holley.com/products/fuel_systems/fuel_pumps_regulators_and_filters/fuel_pumps/efi_fuel_pumps/in-tank_retro-fit_fuel_module/parts/19-360

 
Last edited by a moderator:
I’m looking at going with the Holley Sniper efi kit. Everything seems pretty easy and straight forward except how and where to run a return line. It appears that there is a vapor/breather line that runs from the tank up to the engine bay. Can you use this as a return and then use a vented cap?  Or do I need to drop the tank, drain the fuel, then drill a hole to install a fitting?

The MSD Atomic set up does not require a return line. I have this set up on my car, my wife's car, and four of my buddy's have them on their cars as well with no return line. Just an option.  will put a link from summit racing for the master kit. BTW its half price of what I paid when I installed mine LOL. I have everything to let it control the timing but I have heard all of these systems seem to struggle with that so I have chosen to not go that route yet. Here is four of the cars that it is installed on.

https://www.summitracing.com/parts/msd-2900?seid=srese1&gclid=EAIaIQobChMIxKKln7Hq6QIVCYizCh196AqCEAQYAiABEgI3jvD_BwE



https://www.summitracing.com/parts/...MIxKKln7Hq6QIVCYizCh196AqCEAQYAiABEgI3jvD_BwE
IMG-20191226-190719261.jpg
[/URL]

 
I’m looking at going with the Holley Sniper efi kit. Everything seems pretty easy and straight forward except how and where to run a return line. It appears that there is a vapor/breather line that runs from the tank up to the engine bay. Can you use this as a return and then use a vented cap?  Or do I need to drop the tank, drain the fuel, then drill a hole to install a fitting?

The MSD Atomic set up does not require a return line. I have this set up on my car, my wife's car, and four of my buddy's have them on their cars as well with no return line. Just an option.  will put a link from summit racing for the master kit. BTW its half price of what I paid when I installed mine LOL. I have everything to let it control the timing but I have heard all of these systems seem to struggle with that so I have chosen to not go that route yet. Here is four of the cars that it is installed on.

https://www.summitracing.com/parts/msd-2900?seid=srese1&gclid=EAIaIQobChMIxKKln7Hq6QIVCYizCh196AqCEAQYAiABEgI3jvD_BwE



https://www.summitracing.com/parts/...MIxKKln7Hq6QIVCYizCh196AqCEAQYAiABEgI3jvD_BwE
IMG-20191226-190719261.jpg
[/URL]


 

 


Yes, "returnless" is the way to go.  My Edelbrock E-Street has a high-pressure pump/reservoir for a returnless system.


 

 


Having said that, I would think as long as you remove the vapor canister from the system and simply utilized the hard line as a return line (with flexible FI-rated fuel hoses & clamps to make up the difference), you should be OK.  Hopefully, some of the guys running "return" systems will chime in as to how they made it work.


 
I have Fitech with a sump Robbmc pump. It works great since it has an one quart tank. It uses a return line that needs to be 1/4" because it is very little flow. I ended up using the vapor line because it is larger than that. You have to remove the vapor canister off course. I also took the tank down and replaced the top vent attachment with another pickup tube attachment. I did this because the top vent attachment has a restricted nipple. You could drill this restriction out and it should work without replacing it.

However, the vent line may not be large enough if you are using a standard inline pump. The return flowrate of a sump pump is much less than an inline pump.

Also, if you use the vent line i would make sure to flush it before hand and i would replace the rubber hoses by the engine bay and the tank. They will be dirty for sure.

Sent from my SAMSUNG-SM-G930A using Tapatalk

 
Not specifically on this car, but I have seen people run the return to the filler pipe. That way they can remove the filler pipe, do the plumbing and put it back. I could see that being noisy if nothing else, but it is something people do. Also on other cars, I've seen them plumbed into the sending unit cover. So you can get a new sending unit, plumb it to take the return then drain the tank and install. Again no idea if that would work on this car.

 
Im switching to the Atomic efi in the next month or so. Im going with the Aeromotive stealth tank with 200lph pump.its expensive, but no cutting, measurements, just put it in and plumb it with-6 hose.





My car also has been sitting for 19years and needs a new tank.

 
Im switching to the Atomic efi in the next month or so. Im going with the Aeromotive stealth tank with 200lph pump.its expensive, but no cutting, measurements, just put it in and plumb it with-6 hose.





My car also has been sitting for 19years and needs a new tank.
I have this tank with the 340 pump. It fits perfectly. Still don't have her running yet though, 4 years in...

 
Im working on installing one of the Holley EFI's and I ended up buying a new tank and then this pump will be going into it. It is internally regulated so no return line which is nice. 

40019_2Corrected.jpg

 

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Just wanted to update for the next person. This is what we ended up doing for the return. Used the stock supply line as the return and a new line following the same path as the factory line for the supply. So far so good and no need to drop the tank. 

image.png

 
Just wanted to update for the next person. This is what we ended up doing for the return. Used the stock supply line as the return and a new line following the same path as the factory line for the supply. So far so good and no need to drop the tank. 
For the gas supply, did you follow the same route as the stock line? Did you change the diameter?

 
For the supply, it's using 3/8" and running with the stock line but then up behind the engine with a heat shield where it gets near the exhaust and engine.  

 
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