Tech: Building The Motown LS For Big Power With CPR Engines


There are millions of small-block Chevrolet engines in the wild, and many of those still alive reside within the engine bays of street cruisers and hot rods peppering the streets of America, from small-town to big city. But over the last two decades, the widespread usage of GM’s LS engine architecture has given the venerable small-block a run for its money. As they did with the original small-block platform way back when, the General has amortized the cost of the LS tooling by producing a version to work in many different vehicles ranging from pick-em-up trucks to their flagship Corvette, with varying levels of horsepower and sophistication.

One provision that is consistent across each of the LS platforms is the performance of the modern induction system – it’s leaps and bounds ahead of the dated traditional small-block design. From the initial cathedral-port LS1 cylinder head design which debuted in the mid 1990s to the rectangular-port design used in today’s dry-sump, high-performance LS7 engine under the hood of the Corvette, the GM engineers have proven that pushrod-based performance is capable of big things when treated to a capable set of cylinder heads and intake manifold.

The World Products Motown LS engine combines the user-friendliness of the small-block Chevy with the superior induction system design of the LS engine into one package.

The World Products Motown II LS engine combines the user-friendliness of the small-block Chevy with the superior induction system design of the LS engine into one package.

Dick Boyer and the team at World Products realized that there were many similarities between the old-school and new-school engines which could potentially be combined to develop an option for old-school hot-rodders to retain many of the SBC’s advantages while enjoying the improved induction performance from the LS platform.

The engine block created by the World Products engineers to do all of these things effectively is called the Motown LS – a best-of-both-worlds scenario, as the SBC’s parts are plentiful and inexpensive, while the LS induction system runs roughshod over the SBC’s antiquated siamesed intake ports and center pair of exhaust ports with its modern, horsepower-building design. A complete rundown on the block can be found here.

The 4.400-inch bore centers of the small-block Chevrolet match up perfectly with the 4.400-inch bore centers on the LS cylinder heads.

The 4.400-inch bore centers of the small-block Chevrolet match up perfectly with the 4.400-inch bore centers on the LS cylinder heads.

Martin Marinov and the team at Custom Performance Racing Engines (CPR) recently machined and assembled one of these for EngineLabs, using a variety of well-regarded parts. Follow along as we detail the build process, covering all of the pertinent details and potential pitfalls you need to be aware of should you choose to use the Motown LS as the basis for your next engine build.

What’s Important To Know

Despite the popularity of the LS design in recent years (mainly due to the abundance of engines sitting in scrapyards), there are a number of issues with the design that can crop up for users, especially if they decide to get aggressive with performance goals.

First and foremost, the LS oiling system can be a concern, as the Y-block deep-skirt configuration often causes oil windage issues, especially as RPM levels rise. This problem is part of the reason GM went to the dry-sump oiling design with the LS7 engine.

The Motown LS does away with the problem; by using the traditional small-block Chevy lower end design, oil control is significantly improved and offers the end-user horsepower gains over a comparable LS engine as a result. The Motown LS also provides the ability to use a dry-sump oiling system should the user want to do so.

The Motown LS block features a priority main oiling system.

The Motown LS block features a priority main oiling system.

“People that are trying to make some steam with the LS engine find that it has windage issues. Aside from the oil control improvements from using a regular small-block bottom end, the dyno gains that we’ve seen are in the neighborhood of 30 horsepower with the better oil control of this block design. If you compared the same spec LS engine with the Motown II LS, this design is going to make a significant amount of horsepower over the standard LS,” says World’s Jack McInnis.

Part of the reason the Motown LS exists is due to the fact that the small-block Chevy and LS platforms share common 4.400-inch bore centers, allowing the World team to reverse-engineer both designs, and in the process, pick and choose which features would provide the most benefit to the end-user.

Notable Differences For Motown LS Block

  • Cam Location raised .134-inch over SBC
  • 55 mm camshaft journal size (LS) instead of SBC journals
  • Allows for 4.000-inch stroke crankshafts
  • Uses LS tie-bar roller lifters and spacing
  • Uses LT1-style reverse-flow cooling system (cools cylinder heads first, then block)
  • Main caps located by ring dowels and stepped registers
  • Machining facility is ISO9000 Certified
An important decision came through the choice to use the LS platform’s 9.240-inch deck height; this simplifies the process for intake manifold usage. As the standard SBC uses a deck height of 9.025-inch, this change to the taller deck height was a significant departure from the SBC dimension. This change also necessitates the use of an LS-style piston, but one designed with an SBC wrist pin diameter.

“One of the important things we want people to know about the Motown LS engine platform is that it’s an engine build. Yes, you’re mixing and matching some SBC and LS parts, but once you know what parts you need and where they go, it gives you some great advantages,” says McInnis.

“If you want to put an LS swap into a ’69 Camaro or Chevelle, you may have to change the crossmember to get the pan to fit, the cooling system changes, the engine mounts change, and the bellhousing will need to be adapted to work,” explained McInnis. “On the other hand, with the Motown LS, it bolts right in using many of the existing components all the way down to the use of the SBC accessory drive and power steering. Standard LS swap headers will likely work in most cases, as the deck height is the same along with the bank angle and offset is the same.”

CPR’s Martin Marinov says that the valley plate machining process is critical; if it’s not perfectly flat with the deck of the engine block, the cylinder head will not sit flat upon installation. The top head bolt for each cylinder threads into the plate.

There are some challenges to the build process, though – the CPR team faced them head-on to make the project come together. One in particular is surfacing the open-deck block properly to ensure the head gaskets seal up when the heads are torqued down.

“When you surface the block, it has to be done with the valley plate in place,” says engine builder Marinov.

When you surface the block, it has to be done with the valley plate in place, – Martin Marinov, CPR Engines

“If you’re not used to putting one of these together, you have to mock it up and make sure everything fits together, and then figure out what you need to do in terms of machining,” states Marinov. “They leave the lifter bores undersized as well – those need to be honed to size. A word to the wise would be to mock it up and make sure everything is the way you want it before you assemble it.”

The valley plate not only closes off the lifter galley, it also provides the mounting location for the top five cylinder head bolts per side – thus the requirement to deck the block with the plate installed. Otherwise, the heads won’t sit flat on the deck.

Short-Block Details

For this particular build, the block chosen [PN WPI084081] features a 4.120-inch bore (typically finishes to 4.125-inch), .842-inch lifter bores, and a raised camshaft location of .134-inch, which is plenty adequate for a street engine. We chose to enlarge the bore even more to 4.155-inch to unshroud the valves, improving airflow in the process. With the power estimates we had for this particular engine combination, the nodular iron caps were deemed plenty sufficient for the power level. More serious builds, or those with forced induction or nitrous use, will be better served using one of the blocks with 1045 billet steel main caps. ARP 7/16-inch hardware is standard regardless of the block chosen.

Available Block Configurations

  • PN WPI084080: 3.995-inch bore, .842-inch lifter bores, Nodular Iron 4-bolt main caps
  • PN WPI084081: 4.120-inch bore, .842-inch lifter bores, Nodular Iron 4-bolt main caps
  • PN WPI084081-904: Same as above, adds .904-inch lifter bores
  • PN WPI084180: 3.995-inch bore, .842-inch lifter bores, 1045 Billet Steel 4-bolt main caps
  • PN WPI084181: 4.120-inch bore, .842-inch lifter bores, 1045 Billet Steel 4-bolt main caps
  • PN WPI084181-904: Same as above, adds .904-inch lifter bores

Dropping the forged Scat crankshaft into place and buttoning up the bottom end.

The folks at SCAT Crankshafts were able to pull one of their standard weight 4340 steel forged crankshafts [PN 4-350-4000-6000] off-the-shelf to work in this application. Not to be dissuaded by its off-the-shelf design, this particular crank features a 4.00-inch stroke to take full advantage of the raised cam location, along with 2.100-inch diameter rod journals and 2.448-inch main journals for strength. The forging is also nitride-hardened for added wear resistance, and features straight shot and chamfered oil passages for improved lubrication, as well as lightening holes drilled in the connecting rod throws.

Clevite H-Series main bearings [PN MS909HXK] are used for their excellent performance under demanding conditions. The H-Series bearings were originally developed for NASCAR competition, and have steel backings for strength and enlarged side chamfers for better crankshaft radius clearance. H-Series connecting rod bearings are also installed in this engine – the TriArmor coated bearings [PN CB663HXNDK] are treated with molybdenum and graphite along with polytetrafluoroethylene (PTFE) to reduce friction and drag.

To match up properly with the crankshaft, a set of SCAT’s Pro Sport H-beam 4340 forged steel connecting rods [PN 2-350-6125-2100-SA] were chosen. These rods – the strongest pieces SCAT produces – are from their stroker series and measure 6.125-inch in length and use 2.100-inch rod journals, combined with .927-inch bushed pin holes. For security, the rods are outfitted a special doweled cap for specific rod-to-cap alignment, then secured with ARP 2000 7/16-inch cap screws.

These are SCAT's stroker clearanced rods, which are necessary in this application to swing free of the camshaft. The camshaft is a custom grind from Erson which uses the LS lobe distance dimension.

“A stroker-clearanced rod has a shorter bolt and a low shoulder on the rod itself so it clears the camshaft as it rotates. With a typical LS you don’t run into these issues until you get into the bigger strokes, but this crankshaft has a four-inch stroke and it needs to be done,” says Marinov.

The pistons in this engine are from JE Pistons [PN 311988] and feature an LS-style design with small-block Chevy pin locations. The asymmetrical forged side relief (FSR) pistons allow the use of the 4.00-inch stroke and 6.125-inch connecting rod, to combine with our 4.155-inch bore to displace a total of 434 cubic inches.

The FSR pistons are unique in their use of the asymmetrical design, which uses a larger piston skirt on the major thrust side and a smaller skirt designed to reduce friction on the minor thrust side. These pistons use 1.2 mm steel nitrided top, 1.5 mm Napier second, and 3.0 mm low-friction oil control rings [Ring set PN JG31F8-4155-3]. Double pin oilers, accumulator grooves, and an offset wrist pin design are standard with these forgings.

The forged JE pistons sit .005-inch out of the hole and are manufactured from the company's FSR blanks.

Once you know what parts you need and where they go, the Motown LS gives you some great advantages. – Jack McInnis, World Products

The blocks .134-inch raised camshaft location also permits the use of a 55 mm babbitt-bearing-style camshaft core and shorter pushrod dimensions, thus promoting valvetrain stability.

Camshaft cores are available from Erson, part of the World Products family, with a variety of lobe configurations and lift specifications – McInnis recommends hopping on the phone with one of their technical support staff to ensure you have the right camshaft for your application.

Our custom grind Erson core [PN 115996] was designed to move some serious air. It features an upgraded cam journal size of 2.125-inch, an intake duration of 242 degrees and an exhaust duration of 250 degrees at 0.050-inch, a cam lift of 0.365-inch and a valve lift of 0.621-inch for both intake and exhaust. This core also uses a LS based lobe separation of 115 degrees to match up with the lifter locations properly.

Induction And Fueling

This engine offers deep-breathing capability, and in an effort to show off its performance capabilities, we chose a set of 245 cc max-effort cathedral-port LS1-style cylinder heads [PN 1680] from Air Flow Research (AFR). These “Mongoose” competition series aluminum castings push an incredible 355 cfm and are recommended by AFR for large-bore applications such as ours, displacing up to 454 cubic inches up to 6,800 rpm – right in the wheelhouse for our Motown LS build.

The Air Flow Research cylinder heads feature full CNC porting in the intake and exhaust runners. These 245 cc LS1 castings are the company's top-of-the-line product for this application.

The heads have been treated to the full range of tricks offered by AFR. Oversized CNC-ported 73 cc combustion chambers, intake and exhaust ports, and a competition five-angle valve job combine to promote superior flow up to approximately 6,800 rpm. The intake valves measure 2.165-inch in diameter, while the exhaust valves check in at 1.600-inch; both ride up and down in bronze guides. A set of PAC Racing hydraulic-roller 1.270-inch dual valve springs are held in place by titanium retainers and seven-degree keepers; while Viton seals keep the oil in check during engine operation.

Fully ported CNC chambers are also standard on these cylinder heads.

Fully contoured CNC chambers are also standard on these cylinder heads.

Valve actuations happen courtesy of 1.7:1 roller rocker arms [PN 90097] and pushrods [PN 25755-16] from Howard’s Cams. The direct bolt-on Gen III/IV roller rockers are a direct replacement for the factory rocker arms, and feature a number of upgrades including aluminum bodies, needle bearing fulcrums and roller tops, along with centerless ground pins and rollers. Best of all, they’re made right here in the good ol’ USA.

The Street Retro-fit hydraulic roller lifters [PN 91166] are also from Howard’s, and are carbonitrided and tempered to ensure hardness. The hardened roller wheel is steel and tempered, while the link bars are heat-treated stainless steel. High alloy steel tie bar buttons keep the lifters in place during operating cycles.

Valvetrain gear is from Howards Cams and is common SBC fare.

One of Edelbrock‘s Performer RPM LS1 carburetor-style intake manifolds [PN 71187] rests atop the cylinder heads; it’s designed to allow the placement of a carburetor atop the LS1 V8; as you’ll see in a moment, we didn’t do that, but we still required this dual-plane manifold designed for solid street operation.

The LS1 carb-style intake is from Edelbrock. Here the engine is getting ready for its dyno session.

The LS1 carb-style intake is from Edelbrock. Here the engine is getting ready for its dyno session.

If we didn’t use a carburetor, how did we accomplish fueling this big-inch small-block? With one of FiTech‘s Go EFI 8 fuel injection systems, designed to support 250 to 1,200 horsepower.

The key reasoning behind choosing this specific EFI integrated throttle body system to power our Motown build was our need for its solid performance, more advanced professional features, and to future-proof our system to handle just about anything else we might want to throw at it. Specifically, we were drawn to its broad horsepower compatibility, the ability to connect a laptop directly to the handheld unit and use FiTech’s pro-tuning software t0 make more refined tuning adjustments, as well as on-the-fly ignition timing adjustments directly from the touchscreen controller.

This unique system offers a number of additional advantages, chief among them are its ease of use and self-tuning capability. The Go EFI system initial setup is completed using the in-car touchscreen controller, after which the engine is started and the Bosch 4.2 wideband oxygen sensor reads the air/fuel ratio, sends the readings back to the throttle-body-mounted ECU, where changes to the fueling parameters are made automatically. Eight flow-matched fuel injectors are mounted inside the throttle body, and the system uses GM-style sensors that are easy and inexpensive to replace should there be an issue. In addition to the on-the-fly ignition timing adjustments, this controller also allows for the air/fuel ratio to be adjusted while the vehicle is in motion.

The four-hole Go EFI 8 throttle body injection system from FiTech is self-learning and offers touchscreen tuning options.

The four-hole Go EFI 8 throttle body injection system from FiTech is self-learning and offers touchscreen tuning options.

The throttle body is designed with a universal base to fit any four-barrel carburetor-style intake manifold and a throttle linkage system to work with most transmissions. No external boxes or harnesses are required with the system, ensuring a neat and clean installation. The system controls fuel pump voltage to reduce voltage to the pump under low load conditions to extend the life of the pump – and to cut the noise output and heat generated in the fuel.


Another angle of the FiTech system; it mounts and actuates like a carburetor, but with all of the advantages of fuel injection.

Most interesting about the Go EFI 8 system is the Swirl Spray annular discharge pattern engineered into the design, which FiTech claims will provide complete atomization of the fuel for an effective, clean burn. The annular discharge injects the fuel through multiple points around the entire circumference of each throttle bore, instead of from one single point like a traditional carburetor. This helps to load the air charge with a fuel mist rather than large droplets.

Although it’s not used in this application, the Go EFI 8 is even capable of handling boost up to 21.7 psi, with its 2.5-bar internal MAP sensor, as well as built-in nitrous and boost timing retard strategies, and nitrous and boost-specific target air/fuel options.

Ancillary Parts

No serious engine build would be complete without a full complement of ARP fasteners. The company offers every fastener and more required for this engine platform, from head studs to oil pan bolts [PN 134-1801] to the oil pump driveshaft [PN 134-7901] and everything in between.

Mounted to the crankshaft snout is an SFI-approved, laser-engraved internal-balance small-block Chevy damper from PRW [PN 2535001]. This damper has an accurate crankshaft bore to provide a proper press-fit upon installation, and is manufactured from a billet carbon steel forging. The internal steel inertia ring is surrounded by high-viscosity silicone gel, which battles unwanted harmonics throughout the engine’s RPM range.

One final check of the crankshaft snout dimension, then fitting the PRW SFI-approved harmonic damper.

The Moroso small-block Chevy oil pan [PN 20180] has a driver’s side dipstick location and a deep sump to hold six quarts of engine oil. It’s finished in clear zinc to provide long-lasting good looks and solid performance at a reasonable price. The wet-sump pan clears our 4.125-inch stroke and includes a trap-door baffle to help keep the oil under control.

The oil pan houses one of Moroso’s windage trays [PN 23020] and oil pump and pickup kit [PN 22124].

Checking the oil pan for clearance and pickup-to-pan tolerance.

Checking the oil pan for clearance and pickup-to-pan tolerance.

We have a Davis Unified Ignition (DUI) distributor [PN 12720] and Live Wires spark plug wires [PN 92051] from Performance Distributors. The distributor uses the company’s Cross-Fire cap to help with wire routing – none of the wires cross one another on their way to the plugs. The distributor comes standard with the company’s 50,000-volt DUI coil atop the distributor, and on the shaft rides one of the company’s Carbon Ultra-Poly distributor gears, designed to stop the wear issues associated with bronze gears.

The D.U.I. distributor from Performance Distributors is the small-block Chevrolet style and provides plenty of juice for this application.

The D.U.I. distributor from Performance Distributors is the small-block Chevrolet style and provides plenty of juice for this application.

A complete set of Victor Reinz gaskets are used here – LS-style head gaskets to fit our 4.155-inch bore, an oil pan gasket [PN CS5746], LS-style header gaskets, and LS1 manifold and carb gaskets to finish off the engine sealing.

Additional Parts Required From PBM/World/Erson:

  • Water Return Kit: 63425 [PBM]
  • Valley Plate: WPI1703844 [World]
  • Cam bearings: DURGMP55 [PBM]
  • Freeze Plugs: PBMBKRC [PBM]
  • Timing Chain Set: PBM8981TRC [PBM]
  • Camshaft: ERSE115996, chosen per application [Erson]
  • Motown LS Cylinder Head Adapter Kit for SBC Accessory Drive: WPI703848-K [World]
The fine folks at Proform were up to the task of providing many of the engine’s finishing parts. The company’s fuel pump blockoff plate [PN 141-212], timing cover [PN 141-217], starter [PN 66256], and 35 gpm electric water pump [PN 66225BK] are used in this build.

The water pump is manufactured from die-cast aluminum and is powder coated for corrosion resistance. It can be used in a racing application or on the street, as it’s supplied with weather-tight electrical connectors. A sweet set of Proform’s polished aluminum tall LS valve covers finished off the engine. These valve covers are designed to clear large valvetrain applications, include mounting studs, and have oil-restricting baffles pre-installed.

Last, but certainly not least, are some of the most important parts on the engine – the timing pointer [PN 4936], ExtraFlow air filter [PN 47631] and distributor clamp [PN 5760] from Spectre. The ExtraFlow air filter assembly is designed specifically for throttle body-style fuel-injection assemblies like our FiTech EFI system, as it has a top which allows air to flow directly into the top of the throttle body as well as the traditional position on the sides of the filter assembly. It also uses a drop base to lower the air cleaner 1.25-inches for better hood clearance.

Final checks on the dyno - now it's time to make some noise!

Final checks on the dyno – now it’s time to make some noise!

The Results

Now that we’ve covered what it takes to put one of these engines together, and the specific items to pay close attention to during the process, we realize that it’s just another engine. Even though there are some unique parts, it’s essentially a small-block Chevy with a great set of heads on top.

How did it do on the dyno? Let’s take a look.

After mounting this powerplant to the dyno and making a few partial pulls to let the Go EFI system dial itself in and find the right air/fuel ratio, the Motown’s peak power figure came in at 682.1 horsepower occurring at 6,500 rpm, the top of the rev range – hinting that there may be even more power available with further tuning and higher RPM capability. The peak torque value appears at 5,200 rpm with 603 lb-ft of torque, featuring an extremely broad torque curve showing no less than 551 lb-ft throughout the entire 2,500 rpm sweep of the test.

Put simply this is a fantastic street engine. The guys from CPR did an amazing job with our World Products Motown LS build, it’s extremely torquey and makes killer power for a naturally aspirated engine running on just pump gas.

Article Sources

About the author

Jason Reiss

Jason draws on over 15 years of experience in the automotive publishing industry, and collaborates with many of the industry's movers and shakers to create compelling technical articles and high-quality race coverage.
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