Ultimate OBS 1988-1998 Chevy & GM LS fuel system Swap Guide (2024)

Ultimate OBS 1988-1998 Chevy & GM LS fuel system Swap Guide (1)

This fuel system swap guide will show you all of the parts needed to successfully install an LS engine into your OBS (old body style) Chevy or GM pickup truck.

As the years pass by different generations of pickup trucks gain popularity, as original C10 trucks became harder to find guys started to build square body trucks and further along the popularity of the OBS Chevrolet and GM trucks has increased. With this increase in popularity builders have started to look at swapping LS motors into the trucks to gain the reliability and power only an LSx series engine can provide.

Advantages of LS swapping an OBS 1988 to 1988 K1500 or C1500

When comparing the parts and work needed in completing a fuel system for an OBS LS engine swap to other series of GM trucks like the squarebody or original series old body style owners have the advantage due to this truck platform being originally designed for EFI fuel injection with the TBI system.

This means that you are able to install a high pressure fuel pump directly into the factory sending unit and avoid having to replace fuel tanks. There are special adapters available that allow a direct conversion from the factory TBI fuel fittings to AN helping to keep the fuel system portion as simple as possible.

OBS TBI vortec to LS swap fuel system parts list

Here you will find a complete listing of all of the parts needed to successfully swap both return and return-less style LS engines into your old body style chevy or GM K1500 / C1500 truck.

Return-less style LS swap parts list for OBS (old body style) trucks

The first thing that needs to be upgraded when completing an LS swap for these trucks is the fuel pump. You have multiple options to choose from when upgrading the pump each with there own benefits.

Your first option for an LS swap or EFI conversion with a factory power level up to 450HP is the

Spectra Premium 190LPh Fuel Pump - HERE

For a bit higher flow and support up to 550HP the

Walbro 255LPH pump - Found HERE

If you are producing a bit of extra horsepower the Aeromotive 340LPH is another good option. Again this pump will fit in the factory sending unit. There are other considerations with this pump such as regulator and electrical connections.

Aeromotive stealth 340LPH fuel pump -Found HERE.

Adapter fittings to convert factory sending unit to AN6.

M16 x 1.5 to 6AN - Found HERE

M14 x 1.5 to 6AN - Found HERE

The Hot Rod fuel hose Return-Less LS swap kit, for a return-less system you will need 20ft of hose if mounting the corvette regulator/filter close to the tank. Longer lengths of braided AN PTFE hose are available if needed. You can chose both your hose and fitting colors with this kit.

Return-less LS swap kits by Hot Rod fuel hose - Found HERE

These parts are everything needed to complete this OBS LS engine install from a fuel line perspective. As always if you have any questions you can reach out to us on our Contact Us page.

Return Style LS swap parts list for OBS (old body style) trucks

The parts needed for converting a TBI OBS engine to an return style LS engine can be found below.

As before you will need to replace the factory fuel pump with a high pressure fuel pump. The most popular of which is the Walbro 255LPH in tank pump. This pump is compatible with the factory sending unit and will deliver the flow and pressure needed to supply the LS engine.

Walbro 255LPH pump - Found HERE

For higher horsepower applications the Aeromotive 340LPH continues to be another good option for return-style LS engines. This pump will fit in the factory sending unit.

Aeromotive stealth 340LPH fuel pump -Found HERE.

Adapter fittings to convert factory sending unit to AN6.

M16 x 1.5 to 6AN - Found HERE

M14 x 1.5 to 6AN - Found HERE

A fuel filter will be required in addition to the other parts with this kit, we have both factory style fuel filter options and aftermarket fuel filter options.

Factory style fuel filter with AN adapter fittings - Found HERE

Aeromotive 10 Micron fuel filter (requires 10 ORB to AN fittings) - Found HERE

Holley 10 Micron fuel filter (requires 8 ORB to AN fitttings) - Found HERE

Finally the Hot Rod fuel hose return style LS engine swap kit will complete the needed parts for your OBS 1988 to 1998 GM or Chevrolet LS swap. For a return style swap you will require a 30FT kit to be able to run both the feed and return to the factory fuel rails found on the LS engine.

Return style LS swap kit - Found HERE

Back to blog

I trying to find the correct an fittings for my 92 chevy 1500 fuel pressure line. Going with a 6an fitting. Can someone help me please

Working with a 1990 Chevy blazer.doing a LS swap 2005 5.3. Can you lead me in the right direction for the fuel pump, lines, fuel pressure regulator. Thanks

Working with a 1990 Chevy tbi system. Doing a LS swap 2005 5.3. Can you please lead me in the right direction as for pumps, lines, fuel pressure regulator? Thanks

What determines return or return less fuel system. I have obsb91 gm pickup that I would like to install 5.3 ls I have

I have a 1993 K1500 regular cab Silverado 4×4 with a 5.7 tbi that I am swapping to a LC9 5.3.. I will be using. SSTB intake that does not have a return on the fuel rail. Is their a complete kit from the tank to the fuel rail for this application? Thanks for any help !!

★ Judge.me Reviews

Let customers speak for us

1751 reviews

91%

(1602)

4%

(75)

1%

(22)

1%

(21)

2%

(31)

M

AN-6 Nylon Braided choose your color and 8 Fittings Bundle Deal

Murray Randleman

Good solid product

Well made hoses and fittings with very good online videos.

Ultimate OBS 1988-1998 Chevy & GM LS fuel system Swap Guide (2)

Thank you very much for the positive feedback, it is greatly appreciated!

r

Aeromotive inline Fuel Filters with AN male fittings

rob cush

Great parts and customer service

Always great quality parts and customer response time after products are ordered. Looking forward to getting everything installed and running.
Thanks!!!!

Ultimate OBS 1988-1998 Chevy & GM LS fuel system Swap Guide (3)

Thank you for the positive feedback Rob, the build is looking amazing!

S

SBC to LS Engine Swap Bracket Set

Shawn Cox

Relocation brackets worked perfect

Brackets worked great for my ls swap. I was having clearance issues with the oil pan and subframe, and was able to move the motor just enough to clear everything

Ultimate OBS 1988-1998 Chevy & GM LS fuel system Swap Guide (4)

Good morning, thank you for your feedback. We appreciate the support!

T

Reusable straight PTFE swivel hose end - AN6, AN8, AN10

Tyler Lesjak

Great quality

Effortless install. First fuel system ive plumbed and had zero leaks. Dont need special tools for the ptfe but they may be nice to have if you do a lot

Ultimate OBS 1988-1998 Chevy & GM LS fuel system Swap Guide (5) Ultimate OBS 1988-1998 Chevy & GM LS fuel system Swap Guide (6) Ultimate OBS 1988-1998 Chevy & GM LS fuel system Swap Guide (7) Ultimate OBS 1988-1998 Chevy & GM LS fuel system Swap Guide (8)

Good afternoon, thank you for your feedback. We appreciate the support. Please don't hesitate to contact us if you have any other questions or concerns.

D

Adjustable Aluminum spanner wrench AN3-AN12 Anodized

Dillon & Chad Houck

The perfect tool for the job!

nicely made and fits well in your hand. small enough to fit in tighter spaces under the car to make those final adjustments. Great tool and a must for a simple install.

Ultimate OBS 1988-1998 Chevy & GM LS fuel system Swap Guide (9)

Good morning, thank you for your feedback. Please don't hesitate to contact us if you have any other questions or concerns.

Ultimate OBS 1988-1998 Chevy & GM LS fuel system Swap Guide (2024)

FAQs

What fuel pump for OBS LS swap? ›

Fuel Pump Options

One of the most popular options for these OBS models is the Aeromotive 340 Stealth, a high-output (340 LPH, 90 PSI max), electric, in-tank pump supporting EFI builds up to 850 HP.

What fuel pump is needed for LS swap? ›

Recommended fuel pump - 58-60psi and 240-340LPH flow

Any good electric fuel pump that can provide 58-60psi of pressure to the injectors and a flow rate between 240-340LPH depending on the HP rating of the engine.

Do LS engines have fuel return lines? ›

Return Style Fuel System LS Engines

Any excess fuel not used by the engine is then sent back to the tank through a separate “return” line.

What fuel pressure is needed for LS swap? ›

For LS engines, you'll need a pump that can deliver 58-60 psi of pressure to the injectors, with a flow rate between 240-340LPH (check out these electric fuel pumps from JEGS), depending on how much horsepower you're pushing.

What is the fuel pressure for a stock LS? ›

Everything is handled by a mechanical fuel pressure regulator in the fuel pump module inside the tank. Factory fuel pressure should be about 58 PSI all the time.

What are the disadvantages of returnless fuel system? ›

The most obvious drawback is that the filter is now in the tank, so replacing it is a major deal. A filter that's become clogged with debris means the pump now has to suck extra hard just to get the fuel it needs. This causes low fuel pressure, fuel boiling and pump cavitation.

What size fuel lines do I need for an LS swap? ›

For instance, an 8AN feed line and 6AN return line on a 1000 horsepower gasoline or race gas powered LS with 30psi is sufficient. However, on an E85 combo, we recommend a 10AN feed and an 8AN return minimum for the same setup minus the fuel change.

What year did GM go returnless fuel system? ›

General Motors and Ford started down the returnless route in 1999, and in 2004, GM went returnless on most of its full-size pickup trucks and SUVs with the Vortec 6000 (LQ4 and LQ9) engines, including the Cadillac Escalade; Chevy Silverado, Suburban and Tahoe; the GMC Sierra and Yukon; and Hummer H2.

Does it matter what fuel pump you use? ›

As long as a fuel pump provides the Flow Rate your engine needs at the pressure your Fuel Injected or Carbureted system requires, it will work just fine. It is just a matter of deciding which one works best for your installation.

Do I need a high performance fuel pump? ›

Do I Need a High-Flow Fuel Pump? Installing a high-flow fuel pump is critical if you add forced induction to a vehicle, as in the case of a turbocharger or supercharger, or if you have a forced induction vehicle and increase its output by upgrading the turbo or supercharger pulley to increase boost pressures.

Top Articles
Latest Posts
Article information

Author: Duncan Muller

Last Updated:

Views: 6300

Rating: 4.9 / 5 (79 voted)

Reviews: 94% of readers found this page helpful

Author information

Name: Duncan Muller

Birthday: 1997-01-13

Address: Apt. 505 914 Phillip Crossroad, O'Konborough, NV 62411

Phone: +8555305800947

Job: Construction Agent

Hobby: Shopping, Table tennis, Snowboarding, Rafting, Motor sports, Homebrewing, Taxidermy

Introduction: My name is Duncan Muller, I am a enchanting, good, gentle, modern, tasty, nice, elegant person who loves writing and wants to share my knowledge and understanding with you.