Ultimate fuel system guide for 73-87 C10 & K10 Squarebody trucks - LS Swaps and EFI conversions
LS or EFI swapping your C10 / K10 73 - 87 squarebody truck. This guide is for you.
Tons of guys find our website when researching info on how to do new fuel lines for their squarebody 73 - 87 Chevy and GM trucks. We get asked enough times what else guys need in addition to our PTFE hose kits in order to complete the swap we decided it best to make a write up for everyone.
In this fuel system write up for the squarbody pickup you will find links to what we have found to be the best parts to use in an LS swap or EFI conversion, some installation photos, instructions, and guidance on how to make the fuel system install go as smoothly as possible.
There are many different ways to do a fuel system on any vehicle, these recommended parts and instructions are what we believe to be the best way to ensure an effective, affordable, and long lasting install.
We will give you the parts list first so if that's all you came for you can get in and get out quickly. Note some of these items we don't sell directly so we have linked to the source in which we have found the best price in combination of shipping and product.
Parts needed for all installations
Fuel Sending Unit(s) - Select which side the fuel filler door is located
Conversion fittings to attach PTFE AN fuel lines to the sending unit(s)
1 of each needed per sending unit.
The following fuel pumps are compatible with the Spectra sending units.
Great for factory LS engines to slightly modified and stock engines with EFI conversions.
Modified Engines to about 700HP boosted and 900HP naturally aspirated. (many factors come into play on these ratings so be sure to contact us if you are unsure)
Return - Style LS Engine swaps
We have created a universal LS engine swap kit for return style engines that includes all necessary fittings from the sending unit to the fuel rail. It is assumed you have followed the rest of this swap guide for your C10 or K10 square body truck and are using an in tank pump. Please contact us if you plan on using an inline pump as some other factors need to be considered.
You will need approximately 25-27ft of PTFE hose in order to run both the feed and return on the fuel system. The 30Ft kit is the most common choice for square body LS swaps.
You will also require a 10 Micron in Line fuel filter. We have two options.
Return - Less style LS Swap Kit
These returnless style ls swap kits include all fittings needed to install the returnless ls engine into a 73-87 c10 / k10 squarebody pickup. They include the corvette style filter / regulator as well as the adapter fittings to get it hooked up. Most guys mount this regulator fairly close to the tank and allows them to utilize the 20FT Kit.
No additional filter is needed with this kit.
EFI Conversion - Including Holley Sniper & FiTech EFI systems
The nice thing about the EFI conversion systems is the majority include fittings that are compatible with AN standards. As such one of our regular hose bundles and a 10 micron filter is all you need to get hooked up in addition to the tank, pump, and sending units listed above.
As these systems have the regulator installed in the unit you will require approximately 24-26ft of line. Our 30FT kits are the perfect option for an EFI conversion in your square body C10 or K10 pickup truck.
We have three options for fuel filters.
Other Parts needed
In order to easily install the new line and fittings into your chev or GM C10 / K10 pickup we carry some tools that make the process easier and prevent marring your new fittings.
Now the fun stuff installing the kit's into your 73-87 square body chevy C10 / K10 truck.
When you have the correct parts installation of your new LS engine or EFI system will be smoother than you ever expected.
Hose fitting installation instructions can be found HERE, follow these instructions for the installation of the hose end fittings onto the PTFE hose.
Fuel pump & Sending unit installation.
The fuel pumps we linked to earlier in this article are direct fit into the sending units. The complete install of the fuel pump, sending unit and hard line to AN adapters will allow you to hook up the PTFE hose kit that you choose for your relevant install. You will need to cut off the bubble flare on the end of the tubes in order to install the hardline to AN adapter fittings. Do not cut the center vent port unless you intend to also install a hardline to AN adapter for the vent.
Return-less style regulator install
If your squarebody LS engine swap will be utilizing a return-less fuel rail you will require a regulator. If using a factory or only slightly modified LS engine the most common regulator to use is what is referred to as a corvette style regulator. This regulator also features a 4 micron fuel filter and regulates the pressure to the 58 PSI needed for a return-less LS fuel system.
One common mistake with the install of this regulator is mixing up the feed and return lines from the tank. As shown in the diagram the 5/16" center port is the return while the 3/8" port on the perimeter or outside edge of the corvette style regulator is the Feed. The feed is generally marked by an arrow or a Flow marking. The feed from the regulator to the LS engine is the single center port that uses a push in fitting in 3/8" size. You will require adapter fittings to convert this corvette style regulator to AN fittings and AN ptfe fuel hose. Our return-less LS swap kits include all of the necessary fittings to hook up your PTFE AN line to your regulator/filter.
Running Dual Fuel Tanks
We often get asked the best way to run the factory dual tank setup found on squarebody C10 and K10 pickups. These dual tank installs can be approached a few different ways. If you are running a return-less style LS engine you are able to eliminate the factory switching valve entirely, unfortunately with a return style LS engine this is not possible.
Return-Less style LS engine swap with dual gas tanks
For this install you will eliminate the GM factory switching valve and rely on two corvette style regulators and check valves to direct fuel flow from the correct tank. The fuel pumps are activated one at a time with the dash switch to ensure proper operation. Be sure to use a dash switch from an 87+ squarebody.
You may also need to run relays and/or upgraded wiring for your fuel pumps to ensure you supply sufficient current to the fuel pumps in a dual tank situation. The fuel pumps and sending units listed above will suffice for this install but remember to order a sending unit for both the passenger and driver side fuel tanks.
How to route AN PTFE fuel lines for a dual tank install using an LS Return Less style engine.
Below you will find the routing diagram for this type of install, we also have swap kits available for this type of dual tank install.
When completing this install using on our dual tank LS engine install kits you will need to also use 2 X 3/8 hardline to 6AN and 2 X 5/16 hardline to 6AN adapter fittings for the sending units. Fuel pumps and Sending units are the same part numbers listed at the beginning of this article,
Return Style LS Swap with Dual Tanks
When installing a return style LS engine into a 73-87 chevy or GM squarbody truck and using dual tanks you must use a factory high pressure tank switching valve and compatible dash switch (both from 87+ model years) as the external fuel pressure regulators will not be compatible.
Unfortunately as a result of having to use the factory switching valve the install becomes more complicated and in our opinion we recommend avoiding a dual tank install. The factory switching valve is manufactured out of plastic and the hose barb fittings used are shaped in a way where it is not easily adapted to AN style fittings compatible with the PTFE braided hose.
Due to this in order to convert the switching valve to compatible AN fittings you must use hose barb to AN adapters with EFI compatible rubber hose and hose clamps. The increase in potential failure points increases the danger of this type of install. It also doesn't look very pretty.