They say the devil is in the details. The reason that’s a cliché is because it’s true. But we’re here to take the hassle out of those details. LS engine swaps have become the easiest and quickest way to infuse 21st century power into classic Chevy performance machines. Dozens of stories have been written on the basics—with attention paid to the big stuff like headers, engine mounts, oil pans, and the like. But what about all the remaining details? It’s those niggling little fine points that keep you out in the shop late at night figuring out the best way to make that swap work without just throwing money at the solution.
We’ll cover some of the details that those other stories didn’t tell you—like how to correctly wire that new GM alternator, or what to do when the power steering pump pulley hits the steering box, or where to get those slick fuel line adapters that convert the GM quick-disconnect hard lines to AN hose. Yeah, we gotcha covered.
We will concentrate this story on Gen III/IV engines into ’60’s and ’70’s Bow Tie machines. We’ve been there so we know what works. So hop on board the LS train and take a ride down to Swap Alley!
With LS engines you will be expected to know acronym-speak—like QD, which stands for quick disconnect. GM began using a slick QD fitting on the fuel pressure and return lines right with the first LS engines. These fittings snap in place but require a special but inexpensive tool to disconnect them. These fittings are designed to work with GM’s PTFE (plastic) fuel lines but most car builders prefer to work with AN line.
Several companies like Aeromotive, Russell, and others offer a nice aluminum adapter fitting that snaps 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 makes 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 PNs can be found in the accompanying chart.
LS Gauge Adapters
If you plan on running aftermarket gauges on an LS engine like oil pressure and water temperature, the easiest thing to do is to pick up 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.
Water Pump Play
The 4.8/5.3L and 6.0L LS truck engines are among the most popular engine swaps because they’re less expensive. One down side to using these engines is their unsightly (OK, ugly) tall 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.
All GM LS Gen III/IV engines use the CS130D alternator with its unique connector. To wire this alternator into a ’60’s GM vehicle, Painless Performance 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 8-gauge charge wire, while a 6-gauge is even better. This minimizes charging system resistance and offers the proper voltage to all your accessories.
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 Chevelles and Camaros is in 1969, the Nova replaced the throttle linkage rod with a cable but retained that odd-shaped firewall adapter where the original z-link passed through. The Nova setup bolts the pedal to this 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.
Quality LS plug wires can be pricey. MSD makes an excellent wire for around $80 and even more if you are thinking of relocating the coils. We discovered that the older, mid -’90’s LT1 Opti-Spark engines used the same coil boot and connector as the LS engines. These wires are less expensive—we found a set of Standard Motor Products plug wires 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.
If you choose to go the carbureted route for your street LS, this makes much of the conversion simpler, but you will have to add some type of ignition control. The easiest, simplest, and quickest way to do this is with MSD ignition boxes. For the 24x engines the PN is 6010, while the 58x engines use the PN 6012. 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.
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-’04, 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 i.d. lower hose to the LS engine’s 1 1/2-inch i.d. 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 o.d. water pump outlet. It’s a tight squeeze but it will work.
Truck 6.0L Crank
This is more of a tip when it comes time to buying a used LS engine. The early 1998-’99 6.0L truck engines came with an extended crankshaft flange compared to the usual crank flange, which is flush with the bellhousing flange. These 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 6.0Ls 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. These engines are otherwise the same as the early 24x iron block 6.0L engines.
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 Chevelles, 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 farther 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. CHP covered the complete installation in the November 2015 issue that you can find online for more details. It’s a great idea and not too expensive.
|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|