# Anyone install Holley Sniper EFI? return line size help needed



## michaelrj9 (Jan 25, 2010)

I am looking to install the Holley Sniper EFI on my 1970 GTO 400ci but have a question about the return line size. 

Holley says it needs to be a 5/16 return line, however all the sending units come with 1/4, Is this critical?

I know the kits comes with a bulkhead fitting but it looks to big to put on these sending unit.

Anyone else install the Holley Efi? what did you do for the return line?

Thanks for all the help and or suggestions.


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## PontiacJim (Dec 29, 2012)

michaelrj9 said:


> I am looking to install the Holley Sniper EFI on my 1970 GTO 400ci but have a question about the return line size.
> 
> Holley says it needs to be a 5/16 return line, however all the sending units come with 1/4, Is this critical?
> 
> ...


If you do not get a reply within a day, contact/personal message
*GTO44* 

He is the person who knows and has the experience with the EFI set-ups. Let us all know what you find out.


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## GTO44 (Apr 11, 2016)

michaelrj9 said:


> I am looking to install the Holley Sniper EFI on my 1970 GTO 400ci but have a question about the return line size.
> 
> Holley says it needs to be a 5/16 return line, however all the sending units come with 1/4, Is this critical?
> 
> ...



With the Sniper Master Kit you have to modify the factory sending unit to run the return. 

Feed:
Use the factory feed from the sending unit. From there use a short piece of the efi hose to go to the 100micron pre-filter. Then short piece of efi hose into the fuel pump. Then short efi hose into the post filter. Then from there a long piece of hose to get it to the sniper inlet. 

Return:
For the return line, you can run the EFI fuel line off the sniper outlet to the factory fuel hard line. Then use the hard line as the return. Or use the EFI hose for the return. 

Return Fitting On Sending Unit:
No matter what line you use for the return you'll have to install the bulk head fitting on the sending unit. The reason for this (and the reason why you can't use a factory return on the sending unit if you have one) is your fuel system is now high pressure. High pressure fuel needs to be returned submerged in gas. If not the high pressure spray will aerate the fuel and cavitate the pump. That's the reason for the bulkhead fitting and short length of hose. The bulk head fitting allows you to use a standard -6an fitting. The short length of corrugated hose goes on the back of the bulk head and is zip tied to the sending unit arm. This places the return line below the fuel level. The bulkhead can be difficult to install on the sending unit. I'll upload a few pics of how to do it when I get home tonight. 

Hot Fuel:
One thing I've learned from doing Snipers on different cars is you'll eventually run into hot fuel issues. All the fuel that is not used by the sniper is returned to the tank. The sniper is going to be as hot as the intake manifold. The fuel will pick this heat up and return it to the tank. After about 30minutes or so enough hot fuel has returned to essentially start to boil the fuel. This will cavitate the pump and cause the pump to super heat. This causes the fuel pump to fail and leave you stranded on the side of the road. We've tried everything.... Insulating the fuel lines, Header and exhaust wrap, wood/phenolic spacers, fuel pump pwm controllers, ect. The only thing that actually works and is 100% guaranteed is to run a rear mount regulator. Holley makes one specifically for the sniper that includes your post fuel filter and is set to exactly 59.5psi (which is what the sniper requires). Here's a link. I suggest you buy this and install it before you get on the road. The benefits besides the hot fuel issue is it makes to so you dont have to run a return from the engine. Just come out of the regulator and send the feed to the sniper. Then cap the outlet on the sniper. The return comes out of the holley regulator right back to the tank which it's sitting next to. Less hose, less fittings, no hot fuel. 

Here's a link:
Holley EFI 12-888 Holley EFI Diecast Filter Regulator 3/8" NPT 

I'll upload some pics later on of the sending unit modification.


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## Olds455 (Mar 31, 2014)

GTO44 said:


> Hot Fuel:
> One thing I've learned from doing Snipers on different cars is you'll eventually run into hot fuel issues. All the fuel that is not used by the sniper is returned to the tank. The sniper is going to be as hot as the intake manifold. The fuel will pick this heat up and return it to the tank. After about 30minutes or so enough hot fuel has returned to essentially start to boil the fuel. This will cavitate the pump and cause the pump to super heat. This causes the fuel pump to fail and leave you stranded on the side of the road. We've tried everything.... Insulating the fuel lines, Header and exhaust wrap, wood/phenolic spacers, fuel pump pwm controllers, ect. The only thing that actually works and is 100% guaranteed is to run a rear mount regulator. Holley makes one specifically for the sniper that includes your post fuel filter and is set to exactly 59.5psi (which is what the sniper requires). Here's a link. I suggest you buy this and install it before you get on the road. The benefits besides the hot fuel issue is it makes to so you dont have to run a return from the engine. Just come out of the regulator and send the feed to the sniper. Then cap the outlet on the sniper. The return comes out of the holley regulator right back to the tank which it's sitting next to. Less hose, less fittings, no hot fuel.


Any experience with the Holley in-tank retro pump/sending unit? That seems like it would solve the hot fuel issue.


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## GTO44 (Apr 11, 2016)

Olds455 said:


> Any experience with the Holley in-tank retro pump/sending unit? That seems like it would solve the hot fuel issue.


Just depends on how big the fuel pump is. Most of the EFI retrofit in-tank drop in's and EFI conversion tanks come standard with a 340lph pump. That's a lot of fuel that's going to be returned to the tank at idle and cruising situations. 

Actually the first time I experienced the hot fuel issue with the Sniper was on a big block 440 cuda that had an EFI conversion tank (with a 340lph pump).. It would over heat the pump exactly 35minutes into the drive. In fact it was close to melting the fuel pump relay. We ended up using the Aeromotive PWM fuel pump controller to turn the duty cycle down during idle and cruising. Then goes 100% over what ever RPM you set. Along with the controller we also wrapped the headers... and the full exhaust system.... and moved the fuel lines further away from exhaust... and insulated the fuel lines. All that in conjunction with the PWM controller finally solved the issue. (The PWM controller is actually really nice. It will increase the life of the fuel pump and not put as much draw on the electrical system.) But this was before the sniper rear mount regulator was available. We have not had any issues with any cars since switching to the rear mount regulator. Plus you don't have to buy and mount the 10micron post filter... It comes built into the regulator. I would use this even with a drop-in pump. Now, you are still going to get the benefit of the drop in module.... The pump will run cooler being submerged. It will run quieter from outside being submerged and in the tank. You dont have to figure how to mount the fuel pump and prefilter under the car. You'll have standard -6AN connections instead of coming off a barb fitting. And you wont have to modify your factory sending unit to install the bulk head return adapter. 

Also a quick note, the included fuel pump that comes with the master kit can not be used with a PWM controller. It will burn it up. Fuel pumps must say they are compatible with PWM control to be used as such.

Last thing, If you're using a Holley Terminator X system (or similar) with multi-port fuel injection, you won't have to worry about the return fuel heating issues. The fuel rails wont pick up nearly as much heat because they are stood off the intake by the injectors.


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## michaelrj9 (Jan 25, 2010)

GTO44 said:


> With the Sniper Master Kit you have to modify the factory sending unit to run the return.
> 
> Feed:
> Use the factory feed from the sending unit. From there use a short piece of the efi hose to go to the 100micron pre-filter. Then short piece of efi hose into the fuel pump. Then short efi hose into the post filter. Then from there a long piece of hose to get it to the sniper inlet.
> ...


Thanks for the great writeup. I ordered the regulator and fittings.

If you have pictures of modifying the sending unit that would be great.

Thanks for all your help.


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## GTO44 (Apr 11, 2016)

michaelrj9 said:


> Thanks for the great writeup. I ordered the regulator and fittings.
> 
> If you have pictures of modifying the sending unit that would be great.
> 
> Thanks for all your help.


No problem, and thank you. Here’s some pics that may help. This is from a 66 mustang sniper/efi conversion. You may have more room on your sending unit some mods may not be necessary.

This is part 1… part 2 will be on the next post.

Stock sending unit coming out:









Stock sending unit:











Drilling the hole for the bulkhead. I forget what bit size, holley has it listed in the documentation. This needs to be far enough away from everything for the nuts to clear. This specific sending unit we had to trim off the support metal and grind it flat so the bottom side nut would fit.



















With the bulk head fitting:


















With the return hose in place:









Going back in:










Had to come back out. The nut for the bulk head fitting was sticking out a little too far. The retaining ring wouldnt fit back on. With the fitting tightly in place and sealed, we shaved down the over lapping portion of the nut.









Now installed:


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## GTO44 (Apr 11, 2016)

Part 2…

Im going to show how we originally ran the fuel system with the master kit components encase anyone else see’s this post and decides to go that route. Then ill show the swap to the rear mount regulator. Also quick note. We picked up black braided efi hose for this build. We’re still using the same fittings from the kit. The kit includes rubber efi hose.

Using the contents of the master kit we mocked up where we would mount the pre-filter, fuel filter, post filter setup. The mustang had a nice area for this. Sometimes these may have to be mounted on a framerail ect.



















All mounted. Out of the sending unit with 3/8in efi fuel line. Into the 100micron pre filter. Out of the pre filter into the fuel pump. Be sure make sure you have the pump facing the right direction (or flow). Then into the 10micron post filter. Out of the post filter to the sniper. And you can see the return line going to the bulk head fitting with a -6an to barb fitting. Also put the fuel pump as close to the tank as possible. They are meant to push, not pull.




















With this setup you’ll have a return off the sniper. The bulky piece the fitting is attached to is the built in regulator. Here’s the feed and return lines at the sniper using the included fittings.












Now here’s the rear mount regulator setup…




















Installed in-place of the post filter. The return at the sender is now hooked to the return outlet on the holley regulator. We took the existing return line and just cut it down to where we needed it. It sits a little funny because everything was trimmed to fit the old setup. Works great tho.



















Here’s the engine bay with the sniper, hyper spark distributor, hyperspark coil and hyperspark ignition box.


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## ylwgto (Oct 27, 2009)

GTO44 said:


> Now here’s the rear mount regulator setup…
> 
> 
> 
> ...


GTO44, this is an epic post. thank you! That instal is super clean. I have a few questions for you (sorry to hijak thread)

I've been a bit reluctant to take this on myself due to the fuel line routing, but this clarifies a lot. I too have read about the return filter that simplifies the whole thing, and when paired with an in-tank pump setup it seems like a fantastic solution.

What are your feelings about hard line under the car vs. the rubber or braided EFI line? A friend suggested I use this for as much of the fuel line as possible (Summit Racing® Copper/Nickel Alloy Tubing Part #: SUM-220219-25), but I have no experience bending or flaring hard tubing to mate with Earls AN fittings so have shied away from that. 

Do you remove the original stock hard lines and use the same routing holes through the frame rails, or just leave them in place and mount the EFI tube in a new location?

Do you run the wiring for the pump into the cab and under the carpet like the sending unit wire or keep it external along the framerail?

If too much for the post here, we can start a private convo.

Again, thanks!


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## GTO44 (Apr 11, 2016)

ylwgto said:


> GTO44, this is an epic post. thank you! That instal is super clean. I have a few questions for you (sorry to hijak thread)
> 
> I've been a bit reluctant to take this on myself due to the fuel line routing, but this clarifies a lot. I too have read about the return filter that simplifies the whole thing, and when paired with an in-tank pump setup it seems like a fantastic solution.
> 
> ...


We’ve used the rubber efi hose and the black braided nylon hose. Both work great. We usually remove the stock fuel hardlines. We’ll use the stock routing unless there’s way to run it where its in more ambient air flow path… or if there’s a way to run it cleaner than the stock routing.

Some people like to do new hardines. Nothing wrong with that. They are just a pain in the butt and more time consuming. I like the black braided efi hose for the look.

For the fuel pump wiring it depends how clean you want it. Ive run it both ways… under the car zip tied to the fuel lines. Or the nicer way, in thru the cab, under the carpet, thru the trunk pan with a gromet down to the fuel pump.

If you go with an efi tank or efi drop in unit, you wont have the pre filter and fuel pump to worry about. It wiuld just be directly out to the regulator (which is also the post filter). Super clean setup.

Here’s a few pics of the routing. These 2 examples are the 66 mustang from above and a 71 mach one with a sniper setup. Obviously these have a feed and return in the pics. You’ll only be mounting a feed line if you use the rear mount reg.

Here’s the mach one routing. Not following the factory fuel line routing…




































Same style routing for the 66:


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## ylwgto (Oct 27, 2009)

GTO44 said:


> We’ve used the rubber efi hose and the black braided nylon hose. Both work great. We usually remove the stock fuel hardlines. We’ll use the stock routing unless there’s way to run it where its in more ambient air flow path… or if there’s a way to run it cleaner than the stock routing.
> 
> Some people like to do new hardines. Nothing wrong with that. They are just a pain in the butt and more time consuming. I like the black braided efi hose for the look.
> 
> ...



Thanks for the detailed pics, looks great!

Can you share part # for that braided hose and what hose clamps you use? Assume you just buy barbed adapters for the AN fittings? For the hose retainers, are you bolting all the way through the sheet metal or using self tapping sheet metal bolts?

It's buying all the right fittings and do-dads for the fuel lines etc. that's got my head spinning.


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## 67ventwindow (Mar 3, 2020)

ylwgto said:


> Thanks for the detailed pics, looks great!


 I would agree. Great tutorial on EFI.


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## GTO44 (Apr 11, 2016)

ylwgto said:


> Thanks for the detailed pics, looks great!
> 
> Can you share part # for that braided hose and what hose clamps you use? Assume you just buy barbed adapters for the AN fittings? For the hose retainers, are you bolting all the way through the sheet metal or using self tapping sheet metal bolts?
> 
> It's buying all the right fittings and do-dads for the fuel lines etc. that's got my head spinning.


Thanks! The black braided hose I get from my local speed shop, American Motorsports. I'm not sure what brand it is. It is high quality though. I used to use the cheap amazon chinese hose. Problem is it just doesn't flex like the good stuff. You can see how tight some of those bends are in the pics. The Chinese stuff won't do that. 

I would probably just use Summit brand black braided nylon -6an hose. It's probably close in quality to some of the name brands. 

For the fittings ---- In my situation it just depends what the level of build is. If the customer is on a budget I do the -6an and 3/8"npt barbed fittings. That way its simple and quick to assemble. If the customer is not on a budget and doing a nicer build, I like to use -6an swivel screw on fittings. They look nicer for sure. No hose clamps, More pro. Will hold more PSI. (You can see it on the sending unit return fitting in picture of the 66 mustang above). But each connection has to be done on the vice. So there's more time involved to measure, pull out, make fitting, and re-install. Plus you need a good set of AN wrenches so you can don't tear up the fittings. I got a full AN wrench kit from summit for a reasonable price. Or you can just buy the -6an wrench since that's all you'd be working with. 

The insulated fuel clamps are usually installed with self tappers. If it's a super high end deal we use riv nuts (or nutserts) into the frame.... so a regular bolt can be used, and no nuts are required. And there's no tips of self tappers poking thru the floor board when you pull back the carpet lol.

The only fittings you'll need if you're sticking to the push on fittings are a handful of -6an to barb for the drop in fuel pump assembly (im assuming) and for the sniper inlet... and a three 3/8in npt to barb fittings for the regulator. Oh and a -6an cap (to cap the return outlet on the sniper). And nice hose clamps. Not the dollar store special ones.


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## ylwgto (Oct 27, 2009)

GTO44 said:


> Thanks! The black braided hose I get from my local speed shop, American Motorsports. I'm not sure what brand it is. It is high quality though. I used to use the cheap amazon chinese hose. Problem is it just doesn't flex like the good stuff. You can see how tight some of those bends are in the pics. The Chinese stuff won't do that.
> 
> I would probably just use Summit brand black braided nylon -6an hose. It's probably close in quality to some of the name brands.
> 
> ...



Good stuff. I love the look of the -6an swivel screw on fittings...no frayed nylon or hose clamps. Super clean. I'll have to read up on how to do the hose connections with those fittings, since if I 'm spending the $ may as well make it look slick.

Great info, thanks a ton again.


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## michaelrj9 (Jan 25, 2010)

I was hoping to put the fuel pump and regulator near the fuel tank but the problem I am running into is keeping everything away from the exhaust pipes. What should the minimum distance for the rubber hose and or the fuel pump and regulator be?

You have been a tremendous help.

Thanks


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## ylwgto (Oct 27, 2009)

I think if I do this I am going to go with hard line. Watched some vids on flaring for AN fittings and seems pretty straight forward (



) then bending with a spring tube. Also WAY cheaper, safer under the car and will last longer...and a challenge.

Question: how far into the engine compartment should the hard line go? I imagine a short section of braided hose from the hard line to the throttle body is needed for vibration, but if I'm adding soft line I imagine I could just make it a bit longer and save myself some of the PITA of bending hard line to fit around stuff in the engine compt? right?


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## michaelrj9 (Jan 25, 2010)

I don't think its possible to put everything in a straight line by the fuel tank. You need minimum of 
21-22" for the fuel pump, regulator and pre filter not including if you need to bend the hoses on the the ends. The two tailpipes are in the way. I was hoping to mount the fuel pump on top or bottom of the regulator but the lines will be too sharp of bends keeping it away from the exhaust.

Only option I can see is mounting it in the trunk which I really don't like or along the length of the frame but then it would be about mid Point from engine to fuel tank.

Does mounting it in the trunk seem like a bad way to go? 
Anyone have any other options on where to mount it in these cars? 

Thanks


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