Details and Tips to Make your LS Engine Conversion Easy

Using these parts will make your LS swap that much easier and that much more reliable.

There was a time when LS engines in a lowrider were rare. So rare that when you first saw them you probably didn’t think much about ’em; but things have changed—and changed big time. Today, having an LS engine seems to be mandatory and you either have one, want one, dream of one, or are searching the junkyards high and low looking to score that perfect deal on one.

Aside from the power, the reliability, and the cost-effectiveness—when compared to overhauling and tricking out your stock motor—LS engines are a great way to go if you do it correctly. To add to that, they are inexpensive and quite common, especially if you pick up one of the variants found in older P/Us or SUVs, such as the Tahoe, Suburban, or Silverado.

In years past we’ve seen plenty of LS swaps and while most are clean and fully functioning, we’ve also seen a fair share of them plagued by minor problems—mostly caused by user error during install. With that said, we will be going over some of the basics. By understanding this overview, it will give you a better chance at avoiding, or possibly troubleshooting, any current or future problems.

Pickup Game Strong

With so many LS engines available, the top choice seems to be the ones found in Vettes and the infamous Camaro. But if you’re working on a smaller budget you can always opt for getting one out of a truck. That said, here’s a breakdown on how to properly adapt them from a truck into your car.

Early 6.0L truck engines from 1998-1999 come with an extended crankshaft flange instead of the usual crank flange, which is flush with the bellhousing flange. The early long-crank 6.0L engines were designed to be used with the 4L80E four-speed automatic trans, which will bolt right up. This transmission’s bellhousing and converter arrangement was originally designed to be used behind a small-block Chevy, which is 0.400-inch deeper inside the bellhousing. So GM built these early 6.0-liters with a 0.400-inch extended crank flange. This requires a specific, flat flexplate in order to align with the starter motor. These engines are easy to spot since they also come with iron heads and are otherwise the same as the early 24x iron block 6.0L engines.

Stay Connected

The use of Quick Disconnect (QD) fittings on both fuel pressure and return lines is something that began when the LS engines were first launched. While the fittings snap into place with ease, it does require the use of a special but an inexpensive tool to disconnect them. Now, if you plan on removing it by using a multitude of tools, be aware that any damage can lead to a poorly functioning fuel system. Of course we recommend using AN lines instead of the PTFE (plastic) fuel lines from the factory.

Companies like Aeromotive and Russell offer nice aluminum adapter fittings that snap over the hard line on the factory EFI manifold while offering a simple male AN fitting on the other end. The Aeromotive fittings shown here use female O-ring boss (ORB) ends that use a straight AN thread sealed with a Viton O-ring. We’ve also included a couple of part numbers from TechAFX that make short 24-inch-long PTFE hoses with the proper GM connector on one end. The other end of the hose can be fitted with a TechAFX AN fitting to connect to an AN or hard line. All these part numbers can be found in the accompanying chart.

You Gotta Love Bolt-Ons

The less-expensive 4.8/5.3L and 6.0L LS truck engines are among the most popular engines, but one down side to using these engines is their lanky, tall, and butt-ugly intake manifold. For the older cathedral port engines, it’s a simple bolt-on swap to add an LS1/LS6 low-profile intake. But when you do this, the upright water pump outlet to the radiator is directly in the way. The easiest way to avoid that is to use Holley’s new water pump (PN 22-101) that maintains the proper belt spacing to retain the truck accessory drive but repositions the water pump outlet to the radiator to a lower, forward-facing position. This is a simple bolt-on with no spacers or other modifications necessary. If you have an F-car LS1 pump available, there’s a company called LS Brackets that sells a spacer kit and a relocated idler pulley that will accomplish the same thing. The Holley pump, however, is a simple bolt-on—no mods required.

Amped Up

All GM LS Gen III/IV engines use the CS130D alternator with its unique connector. To wire this alternator into a ’60s GM vehicle, Painless Performance Products makes an adapter (PN 3705) that connects the alternator’s “I” terminal to a charge indicator light on the dash. If you choose to not employ the indicator light, you must use a 50- to 100-ohm, 5-watt resistor inline as indicated on the illustration. This resistor is included in the kit. If the resistor is not used, full voltage will quickly kill the internal regulator. Don’t be that guy! The CS130D is a 100-plus-amp alternator so it’s best to include a suitable charge wire from the alternator to the battery. Powermaster suggests a minimum of an eight-gauge charge wire, while a six-gauge is even better. This minimizes charging system resistance and offers the proper voltage to all your accessories.

Wired For Success

Older, mid-’90s LT1 Opti-Spark engines used the same coil boot and connector as the LS engines. These wires are less expensive, and for example’s sake a set of Standard Motor Products plug wires can be had for $36. The issue, of course, is that the LT1 wires are way too long. But all you have to do is retain the LS coil wire end, cut the spark plug end to the correct length, and use a set of straight spark plug ends and boots. These longer LT1 wires will also work well if you are considering relocating the coil packs off the engine.

It’s Tight, but it’ll Fit

All LS engines place the thermostat on the inlet side of the water pump. The early LS engines employed a dedicated cover and thermostat as one piece, but later engines, starting in 2003-2004, changed to a separate thermostat and housing. This allowed the aftermarket to produce both fixed and adjustable housings so you can reposition the inlet as needed. For example, Spectre sells a simple LS-style housing with a straight inlet (PN 4932) that sells for under $20. Companies with variations on this style include Eddie Motorsports, among others.

The hose diameter for this inlet into the engine is also smaller than the standard 1 3/4-inch that Chevy enthusiasts are conditioned to expect. Summit offers a lower hose bushing that adapts the standard 1 3/4-inch id lower hose to the LS engine’s 1 1/2-inch id For the upper (return) hose, we’ve found that if you cut off a 2-inch length of the original LS upper radiator hose, you can use that as a bushing over the 1.300-inch od water pump outlet. It’s a tight squeeze but it will work.

Adapting to Change

Running aftermarket LS gauges is easy to do, but just make sure to use Auto Meter’s gauge adapter package (PN 5284). The kit allows you to adapt normal, electric gauge sending units with NPT fittings into the factory metric holes. If you would rather use a mechanical water temp gauge, you will need to remove one cylinder head and drill out the metric hole to the standard NPT size for the water temp adapter. You can also drill and tap that small outlet on the oil pan for a standard oil pressure gauge or use the Auto Meter metric adapter in place of the stock oil pressure sending unit. The kit also comes with an electrical resistor to allow the use of a normal tachometer from the stock factory EFI wiring harness.

The Red Box

The simplest and quickest way to go carbureted on your LS is with the use of MSD ignition boxes; PN 6010 for the 24x engines, and PN 6012 for 58x engines. If you’re not sure which engine you have, just locate the cam sensor. If the sensor is at the rear of the engine behind the lifter valley plate it is a 24x engine. If the cam sensor is in the front at the timing cover, then your engine is a 58x.

The beauty of this controller is that you can set your timing two different ways. The simple way is to just plug in one of the supplied chips and they will automatically set a curve. The better way takes a little more time, but with a laptop and the free downloadable Pro Data+ software you can set your own curve.

Accessory Drive

The least expensive accessory drive out there is the truck system. It’s also the longest in terms of depth and the tallest, which sometimes can cause hood clearance problems or issues with steering clearance. With front-steer Chevys, the power steering pulley comes extremely close to the steering box. But there are simpler solutions than searching for a smaller pulley or moving the engine further rearward.

The Corvette accessory drive is what everybody desires but these are expensive and the early F-car/GTO middle depth systems are becoming more difficult to find. Holley realized this and created an expandable accessory drive with spacers to allow you to create an LS1/LS6-style Corvette accessory drive using Holley’s brackets. The mounting brackets that position the alternator and power steering are based on the short Corvette depth. Then Holley uses spacers to push the brackets forward to line up with either the F-car or the deeper truck balancer. This means you don’t have to buy a new balancer. And the brackets accept the early F-car alternator and a truck power steering pump—a wonderful combination of affordable original parts. We’ve listed the part numbers for the basic alternator and power steering brackets and the spacers in the accompanying chart.

Cable Throttle

If you are going to use a factory, cable-driven EFI manifold on your LS engine, you will most likely need to convert from the older solid rod-style throttle linkage to cable. There are plenty of aftermarket cable throttle conversions out there, with Lokar being one of the most popular. If you are using a Lokar, be sure to accurately position the pedal assembly where it passes the cable through the bulkhead fitting in the firewall. If the cable is not parallel it will wear through the bulkhead fitting and eventually stick—not good.

Another option for older Chevys is to replace the throttle linkage rod with a cable but retain that odd-shaped firewall adapter where the original z-link passes through. This setup bolts the pedal to the firewall piece and passes the cable through the firewall above where the pedal bolts in place (see illustration). You will need a longer cable to reach the LS EFI manifold, but Lokar can supply what you need. This is a quick and easy way to connect your throttle pedal to the throttle body using mainly factory parts.


Description PN Source
Painless CS130D alternator pigtail kit 30705 Summit Racing
ACDelco CS130D alternator pigtail PT1235 RockAuto
Holley forward-facing truck water pump 22-101 Summit Racing
Auto Meter gauge adapter kit 5284 Summit Racing
Aeromotive 3/8 female to -08 ORB 15118 Summit Racing
Aeromotive 5/16 female to -06 ORB female 15117 Summit Racing
TechAFX GM 3/8 QD to AN -8 hose 24″ 110652 TechAFX
Tech AFX GM 3/8 QD 90 to AN -8 hose 24″ 110662 TechAFX
Russell -6 AN male to 3/8 GM QD female 640853 Summit Racing
Russell -6 AN male to 5/16 GM QD female 640863 Summit Racing
Lisle QD removal tool 39400 Summit Racing
MSD LS1 F-car spark plug wire set 32819 Summit Racing
MSD 24x Ignition controller 6010 Summit Racing
MSD 58x Ignition controller 6012 Summit Racing
Summit lower hose reducer 1 3/4 to 1 1/2 ALL30240 Summit Racing
Cable throttle linkage from Nova APA-6CBH Ground Up
Holley bracket kit Alt, P/S 20-135 Summit Racing
Holley spacer kit, Standard 21-1 Summit Racing
Holley spacer kit, Middle 21-2 Summit Racing
Holley spacer kit, Long 21-3 Summit Racing