Sniper Conversion - 72 FJ40 - F155 Engine (1 Viewer)

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Joined
Dec 2, 2014
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Missoula, Montana
There are lots of Sniper conversion threads out there, I'm posting my version with the hopes that someone will find this information helpful for their application.
Thanks to everyone who has posted their Sniper conversions, I looked at many threads to piece together my plan for this truck.

I am starting with a 9/72 FJ50, F155 engine. I bought this truck in 2014 with a Weber 38 DGAS and all evaporative/emissions components removed by the PO.
The PO also made some other questionable non-stock mods to my rig so this wont be a concours quality OEM conversion.
The truck runs very well but the hot starts and throttle modulation with the Weber leaves much to be desired.

I am using a Sniper 2300, Redline brackets/adapters, 6AN fuel system, and an in-tank Walbro pump (Tanks Inc PA-5) with a Tanks Inc. Weld in Fuel Pump Recess.
This fuel system will allow me to avoid raising my seats and should manage sloshing/fuel starvation with the in tank reservoir tray.

A couple parts are still on the way but I have most of what I need so lets get started.

Step 1 - Install Sniper Water Temp Sensor and Fill/Burp cooling system.
I used the head port behind the carb (w/redline adapter fitting), there was some sort of evap sensor installed here but this was unhooked by the PO so not sure of it's exact function.
(I wanted to do this with the Carb still operational so I don't have to worry about air pockets when firing the Sniper)
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Step 2 - Remove Carb (incl adapters) and Fuel System
(I dont have a photo but I used a redine fuel pump blockoff plate where the carb fuel pump was located)

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Step 3 - Install 02 Sensor
Note that I have a 6-1 header and I welded in a sensor bung last winter knowing that a Sniper conversion was imminent.
I installed the bung tilted towards the engine per Holley's recommendations and I had plenty of room to install.
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Step 4 - Install Sniper Manifold Adapter and Sniper Unit
(The redline bracket/hardware is very high quality and fit everything perfectly)
(Note Sniper water temp sensor location)
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Continued on next post...

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Joined
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Messages
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Step 4 (Continued...) - Install Sniper Unit

PXL_20230126_052318973.jpg


Step 5 - Install throttle Linkage
(The Redline 1F throttle bracket goes between the remote oil filter mount and the side of the intake manifold)
I was able to shorten/adapt the Weber carb throttle cable setup.
Its not perfect but will work for a while.
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The fuel system will be the most involved portion of this conversion.
Up next in the coming days is to drain/pull/dry the fuel tank prior to cutting/welding.
 

Steamer

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Looking good! Just to mention, I've found the blue shop towels (Scott) to cast off a bit of lint or paper particles. They might not offer the best throat protection.
Looking forward to your progress. Where is your water temp gauge sensor going to go?
 
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I agree that blue shop towels are not the best lint-free solution but that's what I hand within reach at the time.
Though, I don't expect that the 50 year old tractor motor will have issue with burning some lint.
There is now a plastic bag taped over the Sniper manifold until this thing is running.
I typically use blue painters tape but the surface of the sniper is lightly textured so the tape wouldn't stick.

Where is your water temp gauge sensor going to go?

The new water temp sensor plugs directly into the Sniper Unit, it doesn't go to a mechanical gauge but it shows up on the in-cab Sniper handheld screen and the output is used for closed-loop EFI tuning.
My 9/72 F155 engine has three ports (1/2" BSPT threaded):
- One goes to the stock dash temp gauge (Rear most port)
- One goes to the front heater and has a shut off valve which I use in the summer (2nd from the rear - next to the temp gauge sensor)
- The third port used to have an EVAP sensor which I wasn't using, so I pulled it and added the Sniper Temp sensor with Redline Bushing (P/N RL1086, this is 1/2" BSPT male to 3/8" NPT female.)
 

Steamer

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Joined
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Did all of the wiring today.
Went well, need to investigate the low coolant temp sensor error on the head unit. The CTS sensor measures 4.7 KOhms, the harness to the sensor appears to have no voltage, I'll contact Holley on Monday. Anyone else had this issue?

Next is fuel tank mods and fuel lines. The fuel pump plate is delayed so it may be a few days.
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Joined
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Messages
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Update... I do have 5 volts to the purple wire on the Sniper CTS harness. The terminal on the female connector is very small so I didn't get a reading using the leads on my multimeter. I took a few strands of braided wire and stuffed them in the plug and got a 5 volt reading.

Apparently some folks have had issues with dead CTS sensors from Holley, so I ordered a new sensor for 11 bucks.

‎Standard Motor Products TX3
 
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More progress this evening. I realized that I had not run through the initial setup wizard on the Sniper. I did that and it correctly reads TPS, MAP, and cranking rpms. Still no fuel system hooked up but just checking wiring. Still a bad CTS reading but another sensor is on the way.
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Then I pulled the seat frame and tuffy console. It's all on one giant frame that the PO had fabricated (poorly).
PXL_20230131_020248592.jpg

Tank pulled

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Last edited:
Joined
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Messages
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My intent is to remove all of the vent tubes and carb fuel outlet from the tank, leaving only the in tank fuel pump mount (incl supply/return/vent) and obviously the fill neck and fill neck vent. I have had these vents plugged with vacuum caps in the past but they seem to degrade quickly from the fuel vapor.

Has anyone removed these tubes and welded plates over the holes? Not sure if the tubes are attached to anything inside the tank, I doubt it? Was planning on chopping them off flush then cut out with a hole saw. Make an oversized cap and tig weld.

My tank is somewhat pre mangled with some plates welded on top by the PO so I'll go for it unless I hear otherwise.

Thoughts?
I'll drain/rise/soap/rinse dry before I start hacking on it. Also I'll add a bunch of dry ice to the tank before I start cutting/welding so I don't go boom.

PXL_20230131_023634841.jpg


Edit: I should also mention that I'll be running the fuel pump/tank vent to a new charcoal canister with a vacuum actuated valve running to the sniper.
 
Last edited:

Skreddy

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If you have tank venting sorted, you can cut and weld those, or just loop one to another.
 
Joined
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If you have tank venting sorted, you can cut and weld those, or just loop one to another.
Thanks. That's what I was hoping to hear. It's not a pristine tank, but it's also not rusty so I'd rather simplify everything while I am at it.

I've had a couple of the lines looped for a few years now. But I might was well do it correctly for the EFI application.
 
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Couple steps forward one step back....

I drained the fuel from my tank, removed the sender and took a peek inside. The tank is very rusty. Not structural rust but not a tank that I want to heavily modify and drop a new EFI pump into.

I ordered a new "Snorkel" tank from CCOT. It will suit me will because I was planning on removing/covering the existing vent pipes in my tank. The snorkel tank only has the carb outlet and no evap house connections so it will be much easier to modify.


Since I couldn't do any tank work I installed a new throttle cable (Lokar TC-1000HT). This worked well because it's 24" and you can easily make it shorter. My cable is probably 12" or possibly less.

I also in installed the Redline charcoal canister and ran most of the vacuum/evap lines thru the ac Delco 214-2294 evap vacuum valve.

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Joined
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Thanks to @TEQ for the charcoal canister evap routing diagram!
View attachment 3117059

Above shows how I replumbed everything.

The rig seems to be running fantanstic, so I think I got it right.

Too soon to tell if the fuel smell is actually gone though.

I was able to use one of the original mounting brackets from the OE charcoal canister, slightly elongating the mounting holes, to hold the slightly larger, lighter plastic Delco canister in the OE spot.

I ran the manifold vacuum via the old metal fuel line that runs behind the engine on the firewall, reducing a bit of clutter.

The new TRE in-tank pump is silent compared to the POS Walbro, which makes me extra happy.
 
Joined
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Messages
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I received the replacement coolant temp sensor (‎Standard Motor Products TX3) in the mail, plugged it in and voila, low Low CTS error gone on the Sniper screen.
The sensor was only plugged into the harness (not installed in the motor yet), but it worked!
I held the sensor in my fist for a couple seconds and it went up 2 degrees so it appears to have fixed the problem.

Folks have had consistent issues with the CTS sensors sent from Holley. After reading about these issues I didn't even bother calling Holley for a new one.
I opted to spend 11 bucks on the compatible sensor that people have had good luck with on Sniper conversions.
This sensor is readily available at most auto parts stores as it is a standard General Motors temp sensor (Many different engines from 1985 to 2014).

Even if the Holley sensor "works" there are some videos with a direct comparison to the Tx3 where the Holley sensor is 20 degrees off.
Of course the ECU will self learn and tune around this inaccuracy, but its easy to replace with the better sensor.
 
Joined
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Messages
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Did what I could this afternoon until the new fuel tank arrives this week.

Installed the new CTS to the head. It reads correctly and confirms that my garage was cold! (28 F - before the heater got going)

Sorted the rest of the vac lines, PCV line, and evap line. I am using the OEM fuel hardline for the evap.

Ran fuel pump wiring under the truck into the cab through a new grommet.

Installed most of the fuel lines back to the cab entry. I ordered 10 more ft of 6 AN hose (started with 20 ft) and a couple bulkhead fittings for going through the floor. The OEM hardlines we're removed by the PO, so I went along the firewall. I am running a filter sock on the pump, then a 40 micron filter under the truck and a 10 micron filter on the firewall.
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I got a ton done today. Some parts arrived and I had time to work. First was the air cleaner, I originally had a 14" round unit but it didn't fit. I bought my rig with a Weber carb so the OEm air cleaner was MIA. Hooked up the valve cover vent with a 90 degree gates 5/8 is" hose which reduces to 3/8" and the Weber style elbow that I had on hand. This air cleaner fits great, Eddie Motorsports MS-215-20BK. It's a great option if it your aren't going OEM. Fits great between the valve cover and master cylinder. Of course I had to put some stickers on it, I can't have anything that large and shiny on the rig...
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Joined
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Messages
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Joined
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I had enough room to squeeze this recess in between the tank baffles. Tank was 18ga and I welded it up with a thousand spot welds with a MIG and 0.024 wire and a spot timer. It worked great I didn't blow through and only had 1 pinhole to fill after pressure testing at 8 psi with soapy water. I also tack welded in the backer plate inside the tank before welding the recess on. You have to be careful clocking the level sending unit and the pump recess tray but there is enough room barely.
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Joined
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Messages
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After some touch up welding it was time to build the fuel pump unit.
PXL_20230211_220127680.jpg

The Tanks inc unit needs to be trimmed to the depth of the tank. That was 7.5" after the recess was installed. Then the fuel
PXL_20230211_220134427.jpg

Then the fuel pump unit was installed to verify fitment.
PXL_20230211_225408663.jpg

This is a Walbro in tank pump. The only deviation from the instructions was welding on the reservoir tray. They say to attach it with a single bolt but that does not seem adequate.
 

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