EFI On A 72 Rallye

[Rallye]

So I am a little put off by my stock Thermoquad 6139S carb. Just doesn't seem to run that smooth and is a hard start! Been rebuilt too many times!

I am considering and leaning towards installing a Holley Sniper EFI system.

Thoughts? Good/bad idea?

[7212Mopar]

Decide early if you want the efi to also do ignition timing control. With efi, tuning is done through the handheld, much easier to do. Cold start no problem. But probably not a good idea if you have a factory correct HEMI or six pack car.

[Dakota]

I did the EFI swap and am quite happy with it.  I used a basic FiTech unit (no timing control), so my comments are based on experience with that system but I believe you'll run into similar issues regardless of the vendor.   

You'll need to add an electric fuel pump to get the needed increase in fuel pressure.  An external fuel pump is easier to install but noisier.   An internal fuel pump is quieter but will likely involve modifying your gas tank or getting a new tank set up for EFI.   

For the FiTech system, you have to let it do a "prime shot" by turning the key on and then waiting about 5 seconds for the fuel pump to cycle on and off before starting the engine.   This is its substitute for having a choke.  The duration of the prime shot is the same during cold or hot starts but the amount of fuel delivered is set by the computer or through manual inputs from the hand-held device that comes with the system.  I got in the habit of turning the key on and then getting my seat belts situated while the fuel pump cycles. 

I added a relay in the engine bay for powering the fuel pump.   The firewall connections for stock wiring have a nasty habit of degrading over time, so the increased electrical load from a fuel pump is best directed elsewhere. 

If you add an electric fuel pump, strongly consider adding an inertia switch or some other means to cut the pump off if your car gets in an accident.

I believe most/all of the EFI systems will also require an oxygen sensor added to the exhaust.

In the case of FiTech, the self-tuning doesn't begin until the engine temp gets above 170 degrees, so make sure your thermostat is compatible with whatever is needed.   I missed this "little" detail ahead of time and ended up having to change my thermostat.

The FiTech unit includes a water temp sensor, so you'll need spot to install it.   I'm running a stock intake manifold and thermostat housing, so there weren't any "extra" spots.   I ended up lengthening the wiring on the sensor and threading it into what would normally be a hole for a block drain plug.

Yeah it's a bit of work but for me the results were worth it.  Or I guess you could just buy a new carb  .    Either way, good luck with it!
 

[Rallye]

That is good information. I have looked at the Holley Sniper and the electric fuel pump actually replaces the sending unit of the original tank. And they have the blank off plate to remove the mechanical fuel pump. It is also a returnless system which is easier to install I think? And yes oxy sensor, water temp fitting and Hyperspark distributor and spark box. The cut off fuel switch is something I didn't think about! Very good point!

[Skdmark]

I installed a Sniper setup on my 318 in my 71 Barracuda along with an LD4B intake last year. Takes a little bit of planning up front but goes together pretty well. I also used Holley's in-tank OEM pump and distributor setup for timing control. I also added a shock sensor off of Amazon to kill the fuel pump in case of an accident (can also double as anti-theft device). I was able to wire it up so nothing was changed on the factory harnesses. There are some things electrically you will need to do that are specific to a Mopar install. The whole thing is completely reversable.

Runs smooth, starts easy and is snappier. This year I plan to dig into the programming a bit more with their software.

Here's a couple of posts I did on it starting at reply 52
https://forum.e-bodies.org/your-restoration-project-roseville-moparts/10/71-barracuda-ev2-h5xv/17032/45

If you have any questions let me know.

[Rallye]

Thank you! I will check it out!

[Rallye]

Looks like I'm about to do almost the same thing you did! Same fuel pump and all! Except I just had the original 4 barrel intake put back on the car when the motor was rebuilt! The Holley rep recommended I get the car running with the new Sniper set up and then tackle the Hyperspark distributor and spark box. Said it would be an easier install! We will see! Really appreciate the information!

[worthywads]

Looks like I'm about to do almost the same thing you did! Same fuel pump and all! Except I just had the original 4 barrel intake put back on the car when the motor was rebuilt! The Holley rep recommended I get the car running with the new Sniper set up and then tackle the Hyperspark distributor and spark box. Said it would be an easier install! We will see! Really appreciate the information!

I did the sniper last summer, including the in tank fuel pump and Hyperspark programmable distributor (MSD), and absolutely love it.  All at once, not in steps like Holley recommended.

Had some trouble initially with bad spark plug wires creating interference and sputtering, once I swapped to MSD Super Conductors it's been smooth running for 3000 miles.

I tucked the hyperspark control box inside left of the brake pedal up and out of the way.

Also ran the wiring to the fuel pump through the plug for access to the shock, and kept all the wiring inside, instead of outside like Holley glossed over.

I also went with the progressive secondary linkage to give a little more light throttle control.

https://www.summitracing.com/parts/QFT-43-2QFT

[Rallye]

Holley recommended the throttle extension to provide easier pedal push and throttle/kick down cable brackets too! We will try! It's all returnable if I don't need it! Lots of good information here! Thank you guys!

[worthywads]

I also swapped my original 5/16" fuel line with 3/8", but in hindsight even with about 400HP 360 I bet the 5/16" would have kept up, but some peace of mind with new over 50+ year old tube.  The in-tank fuel pump has a stepped hose barb that allows either 5/16" or 3/8" hose for the little 5 inch jumper hose from pump to hardline.

Here are a few other things you will need.  Obviously if you stay with 5/16" hardline use 5/16" equivalent.

Plug for the fuel return port you won't need with in tank pump.
https://www.summitracing.com/parts/EAR-AT592906ERL

Tool and plugs to waterproof all of the connections on some of the electrical plugs with extra wire space for sensors you won't use.
https://www.summitracing.com/parts/HLY-567-101

Connection for 3/8" rubber line between fuel hardline and sniper.
https://www.summitracing.com/parts/EAR-750166ERL

You'll also need an inline high pressure fuel filter, I went with this one.
https://www.summitracing.com/parts/ear-731166erl?seid=srese1&gclid=CjwKCAiA4KaRBhBdEiwAZi1zzlMyKOUCXKxJXFFgDB2d0EbHvuKYa-b4A0yFYO5blGD_LKudK_Nr7RoC8D4QAvD_BwE

[worthywads]

Holley recommended the throttle extension to provide easier pedal push and throttle/kick down cable brackets too! We will try! It's all returnable if I don't need it! Lots of good information here! Thank you guys!

I was able to run the same throttle cable and kickdown linkage that came with the original 318.  I did make a short 3/4" link because the cable came up about 3/4" too short.  I can take a picture including mods to kickdown linkage.

[Rallye]

I was thinking the original linkage would work too but my son-in-law convinced me to order those parts. And return if not used but would have them if I needed them! Did order the filter and tool from Summit just now! Holley's filter is on back order until May! Actually the same one!

[Fern]

Lots of good info here.

[Skdmark]

I was thinking the original linkage would work too but my son-in-law convinced me to order those parts. And return if not used but would have them if I needed them! Did order the filter and tool from Summit just now! Holley's filter is on back order until May! Actually the same one!

This is what I used when I added a the LD4B 4bbl intake to my 318:

A 71-73 340 4bbl throttle return spring bracket and the 72-74 340/360 4bbl throttle cable bracket and new throttle and kickdown springs. From Holley I installed one of their 20-7 Chrysler throttle linkage brackets on the Sniper. From the original 318 2bbl I used the one-piece kickdown lever, the linkage assembly and the throttle linkage stud.  I did need to put a Z bend into the slotted bracket to get the new offset aligned. The kickdown lever was about 2 inches short so I picked up a Holley 20-41 Ford  kickdown lever extension to fill the gap. All I need to do was drill one Let F sized hole a little further back to make it work. The kickdown extension has two ears that I'll peen over to lightly clamp onto the kickdown lever. Stock throttle cable works.

since taking this picture I repainted the slotted bracket and painted the throttle cable bracket.