That’s what the Fuel filter is for! 
Few questions. 1: when wiring the sending unit returnless fuel pump 4 wires did you run the 2 black wires to ground or one all the way to the battery like the diagram shows? 2: did you use the original 2 wires going to the sender for the power “blue” wire and gage “purple” wire or did you run the blue wire from sniper harness to tank? 3: where did you put your temp sensor? I’m thinking that i will be putting mine in the intake where current one is and just monitoring temp on the handheld. Don’t see any other spots to put another one. 4: i have the stealth 4150 style sniper and it says to feed both ends or injector rails like a dual feed carb… true? Thanks in advance!
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I’m not sure why Holley wants that one ground wire ran all the way back to the battery. I’m using a different EFI tank+pump combo, but I terminated both ground cables to a chassis ground near the tank. This has worked fine on my car.
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Blue wire from Sniper goes to Grey wire on pump. I think I only had one wire going to the sender for the fuel gauge (which I connected to purple wire on pump). If you have an XR-7 I think you’ve got an extra wire for the warning light.
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Temp sensor in place of the gauge sender in the intake manifold. Accuracy is far more important for the EFI temp sensor, you can move the gauge sender into the port on the thermostat housing.
- You do need to fuel the front and rear fuel rails, you can use one of these two:
Bowl Connector Hose for Sniper and Terminator X Stealth EFI System | Ships Free at EFISystemPro.Com | 534-236
Bowl Connector Hose for Sniper and Terminator X Stealth EFI System | Ships Free at EFISystemPro.Com | Unbraided Vapor Guard Hose
- Grounded to wheel well flange near where the main rear harness comes from the front.
- Run the sniper fuel relay blue wire thru the interior with the car main rear harness. Had to extend the blue wire a couple of feet in the trunk. Unplugged the original fuel sender harness in the trunk and used a bullet connector on the new purple sender wire to plug into the original trunk harness yellow wire connection.
- Used a brass “t” fitting from ace hardware along with a 1/2” nipple to screw into original temp sender hole. Then screwed original sender into one end and new sender into the other. I don’t like the look of it at the moment, but will paint black to see if it looks better or come up with another solution in the future.
- No need to dual feed mine, but if the instructions say to dual feed, you should. I am feeding the passenger side front of mine and the other three including rear regulator /return feed are capped off.
I still want to clean up some wire routing and I am still running my Duraspark distributor.
I messed up pressing on a new steel gear on the hyperspark distributor and slightly bent the top tip of the distributor shaft. I have a new shaft coming for me to try it again.
(Comp cams steel gear inside diameter is about 2 thousands too small and my 20 ton press made it go on anyway which bent the shaft a little) next attempt will be after sanding out at least 1 thousands of ID material, heating up the gear and then pressing it on the new shaft.
I got it warm enough to actually do some self learning on a couple of drives, let it import the new learning info to the base table and she is really running good! I still want a few more learn sessions to really dial it in prior to switching over to timing control.
Jay, thanks for the heads up. I just measured the hyperspark as compared to my current duraspark and it looks like about 1/2 inch taller. I don’t think it will be an issue for me. I will certainly find out before too long. 
This post has got a lot of good information. I just posted a separate lengthy description of my experience with the Holley Sniper Stealth, MSD 6EFI ignition, and the Holley dual sync distributor with timing control on my 1970 Cougar 351C-4V.
Link: https://cccforum.discoursehosting.net/t/holley-sniper-and-msd-ignition-conversion-70-351c-4v/13887/1
70xr7tom, what link do u look under to read about it?
Should have listed that. Edited initial post to include it. Also below
https://cccforum.discoursehosting.net/t/holley-sniper-and-msd-ignition-conversion-70-351c-4v/13887/1
Can we use the pipe plug in the block next to freeze plugs for the temp sensor? There are 2. One at front ps and one at ds rear. Just need an adapter
Aren’t those oil plugs?( I might be wrong, but that’s what I always thought they were)
Nope. Coolant! I about got drowned when i took it out and i had drained the coolant out of radiator already😀
I’ve decided to put the efi sensor on the intake and move the original sender to the ps front block plug. Easier to extend one wire vs the weatherpak connector on efi sensor
Nice! That may be my solution to the ugly brass t fitting as well. Thanks! 
Let’s hope that works!. Went to ace hardware and got a 3/8Fx1/4M connector. Opened the center 5/16"hole a bit to allow the sensor to to fit down inside easier.
Another approach that assures that both temperature sensors are on the outlet coolant flow stream to the radiator is use the existing location for the EFI and install a radiator hose adapter above the thermostat in the hose to the radiator for the temperature gauge/warning light. I also shortened the vertical leg of the radiator hose. I was uncertain about the plug in the intake manifold forward of the throttle body and it was also directly under my fuel supply line. The use of the extra manifold connection is probable better if you can get the sensor tip down into the coolant flow stream but this is an option.
https://www.summitracing.com/parts/atm-2283
True. Or a much cheaper alternative is the thermostat housing that has a threaded port in it for the sender!
Just a clarification because I’m thinking about doing this on one of my Cougars, I thought with the Holley Sniper EFI unit, you didn’t need a CD box as long as you were using either the matching Holley dizzy (forget if its the hyper spark or the dual sync). I’ve always been a carb guy so figured I’m missing something obvious…? It may be as simple as I’m looking at the Super Sniper, which already has a throttle body ecu mounted. Although, I thought I thought they all did had the self tuning ecu. Edit: I’m also looking at the Holley EFI sniper fuel tank. Sounds like the pumps are internally regulated and I wouldn’t even have to run a return line? My battery is already mounted in the trunk so looks like a simple conversion.
You can use the included coil driver module, but you’ll get better quality spark with the Hyperspark CD box. The distributor you need is the HyperSpark, the Dual Sync is overkill because it also provides cam signal which the Sniper doesn’t use.
Will the Hyperspark distributor and CD module support variable ignition timing with the Sniper? Is the distributor available in a short profile like the original '70 Ford 351 distributor?
Yes you’ll have timing control through the Sniper with the HyperSpark setup. Not sure on the height of the distributors, but they have a model for 351W and 351C: