Here's how I did the Walbro 255L fuel pump install on my 1979 C3.

~$100 - I purchased a new 1980-1982 C3 Corvette fuel level sending unit/filler assembly (less fuel pump). It's stainless, which is a nice upgrade from the factory steel (rusted completely out) fuel sending unit that was in my 1979.
~$110 - I purchased a Walbro "kit" for a TPI car (probably intended for a TPI camaro).
~$10 - I purchased some fuel resistant shrink tubing from McMaster
~$220 total invested

The only modification I had to make was to cut and solder the fuel pump plug. The 80-82 pump must use studs because the wires had ring terminals. I cut the studs off and soldered in the Walbro connector.

When I started my project, I originally purchased the Holley drop in unit but when it showed up, I found it didn't have a provision for a return line. I refuse to run a deadhead fuel system as I've always found return style to be more consistent in psi and to eliminate hard starting issues. So that wasn't going to work. Plus, the Holley unit was $370!

My fuel tank and lines were rusted out, so I'm installing a new fuel tank and stainless fuel lines at the same time. I'm using lines from a 80-82 here as well, which will give me a 3/8" feed and 5/16" return. This is the same feed/return sizes which are on my C5 and they have been shown to support 650+ rwhp on a Walbro 255 pump. The regulator is mounted after the Sniper EFI TB in the engine compartment.

 

Absolutely nothing wrong with what you call, "Dead head". Fuel line. Starting or otherwise. If you have the correct pressure fuel to your injectors. It works. And I am absolutely certain that pressure doesn't vary much at all because your running 10 feet of line.

 

Pretty cool.......but remember that Holley wants 3/8" line for the return as well.......
Now I put one on a K5 blazer.....used an L-98 tank pump as a "lift" pump and the Holley pump went inline.......we used the stock 5/16" return line and it was fine.....but your results may vary.

Jebby

 

I'm speaking from experience, but you are certainly entitled to your opinion


If the return is too small, the pressure is difficult to control as the line itself becomes a restriction (like a second regulator). But this tends to only be an issue when the pump volume far exceeds the engine's fuel requirements. In 20+ years of doing this, I have yet to see this occur on a 255L pump. This is one of the reasons fuel pump manufactures say it's important to match the fuel pump capacity to the engine. A 1000L/hr pump on a 289 is just going to be a hassle.

 

Yes, fuel injection 101....but there is a reason they spec the same size......probably to eliminate warranty claims......but the regulator is in the actual Sniper unit just before the return....IDK....just told you to be aware of it......I had zero issue with 5/16 and the guy has been driving it for 6 months.
The other thing is.....have you verified the Walbro will push 58psi? This is what the Sniper needs....

Jebby

 

Holley has to deal with people who have zero experience with FI, so requiring 3/8 feed/return keeps them from having to deal with constant calls and warranty issues.

I’m running the Sniper Stealth, not the regular Sniper. It’s the one that looks like a true 4150 and doesn’t have an internal regulator. My regulator is mounted on the firewall.

The Walbro 255L will go well above 58psi. I think it’s max working pressure is in the 90psi range, but flow is nonexistent at such a high pressure. I’ve been running the 255 on nearly every vehicle I’ve built for the last 20 years.

 

How did you connect the fuel lines to the 82 Sending Unit. Can you use PTFE hose and clamp at the sending unit end, I am thinking of make a AN6 to PTFE hose end to connect to the hardline and clamp the other end on the sending unit.

Or should a different type hose be used due to clamping on the sending unit end ?

 

Are you talking inside the tank (from the pump to the sending unit) or outside the tank (from the sending unit to the fuel lines on the frame rails)?

On the inside of the tank, it's just a length of and two band clamps.

Outside the tank, I'm just running regular fuel injection hose from the sending unit barbs to the fuel lines on the frame. Again, nothing special.

I will say that both of my hard lines were rusted and needed to be replaced. In addition, the factory return is 1/4" (which is way too small for a return) so I'm also upgrading it to a 5/16" hard line. Even if my factory lines had been good, the return would need to have been replaced.

 

Outside of the tank. Sending unit to hardline on the fuel rails. Ok I will source EFI Rated rubber style hose with EFI complete clamps on both ends.

The only thing I will change on the inside is extend the return line lower in the tank.

 

I did the same thing about 3 months ago to my 78 which is getting a 5.3 LS with a cam. Went with the walbro 255 high pressure and used 3/8 single -6AN PTFE hose with a corvette wiz filter to give me the 58psi deadhead with a short return at the tank. I just finished up running new 12 gauge fuel pump wiring and ground which will be controlled by the Holley terminator X EFI (a lot like your sniper). 255 is good for like 600whp NA.

for whatever it’s worth on my 87 firebird I’m running the stock sending unit which has 5/16” return hard line and I’m running a 450lph walbro in the tank at 43psi but it’s a turbo 5.3 that makes 700hp daily on the street. I have no fuel pressure issues with that return and I can adjust it down below 40psi very easily so your 5/16” is more than fine trust me. That 450 puts out almost 2x as much fuel as your 255.

only thing you have to worry about with our tank setups is the fuel slosh problem and the pickup not having fuel. Without a intank baffle it’s hard to keep fuel at the pickup on turns and when your around 1/4 tank. Others have used a hydramat at $140+ which works well but my reading has showed it’s bad for the pumps as the micron rating is too small and causes premature pump failure. Hydramat is like 15 micron pre filter when you normally want a 100micron pre and 5-10micron post filter so the issue is pump has a restriction on the suction side which is the easiest way to kill an EFi pump.

 

So how did you mount the pump to the unit. I don't see anything holding it in place ?

 

You don't need to. The bottom of the pump has a metal holder with a rubber isolator that interlocks with the metal base. The hose above it that's on the feed line (short rubber submersible line) keeps the pump locked in place. I have and standard practice is to use a Stainless hose clamp so secure it to the return line which is what the metal pump base holder is welded to. On mine just like the OP's there is a gap between the pump and return line and my walbro install kit did not come with a pump "vibration" sleeve which is basically a rubber/foam type sleeve that slides over the pump. If the pump was closer to the return line or I had something to fill the Gap I would have put a worm clamp on for added security. However It is not needed and this is how OEM did it for a Long long time with no issues.

 

The rubber base piece is around the pump body and it has a lip that fits in the metal base on the sending unit. Ultimately, it's the fuel hose that keeps everything together as it's putting downward pressure on the pump (pushing it into that metal base).

How I've done it is 100% how it is done on a 1980-1982 C3 from the factory. A lot of cars don't even have the bottom metal base, rather the pump just hangs on the fuel line.

 

Here's the Holley setup for a 1973-1987 GM Truck.
HOLLEY 1973-1987 GM C/K SERIES MUSCLE TRUCK EFI FUEL PUMP MODULE

It doesn't even have a base, rather the pump just hangs on the hose. Again, OEM did it this way and Holley could certainly "improve" the design if they felt the need.

 

All the TPI cars (corvette, firebird and camaro) had similar designs and they all have the same metal base attached to the return line. Normally when I do the pump installs I put a worm clamp on it, especially when I do a walbro 450lph pump install which have a fat/wide bottom and you can't use the isolator in the metal base. The hose clamp is just extra security however like you said the pressure feed hose and the base keep the pump from going anywhere.

 

Have you ever noticed any increased noise due to the band clamp?

 

That's because there is no return line which is what the base/bracket would be affixed to. I prefer to have the base as it makes the stress on the rubber line less susceptible to cracking when the fuel sloshes around in the tank pushing the pump around a little.

 

Again, if Holley felt a "need", they could certainly add a bracket off the feed line or figure something else out. Yes, the base is preferable but clearly not "necessary".

 

Nah, Not that i'm able to notice. I haven't had a 255pump in any of my cars for a LONGGGG time but I remember them being rather loud due to the gear rotor type design. The aeromotive 340 and walbro 450s are whisper quiet (turbine style pumps), you literally don't even know they are on except when I hear the noise as heck aeromotive regulator prime or see pressure on the gauge.

 

The aeromotive 340 is what I am mounting. Able to be used with a PWM controller.