The cam used in our test engine...
The cam used in our test engine had a standard small-block diameter, not the larger, 55mm size of the production LS cam-but the Motown II/Motown II LS blocks can accommodate a 55mm cam. Lift and duration specs are 0.650/0.660-inch and 250/255 degrees, respectively.
Inside the block, LS-style dished pistons are matched with the Warhawk cylinder heads. They use production-type metric piston rings, which appear to work very well in the small-block, with minimal friction. The connecting rods and crankshaft are off-the-shelf small-block parts. The 6.125-inch-long rods don't even require machining in order to be pinned to the LS pistons.
The Heads And More
The heads used with the Motown LS block are World's Warhawk LS-1 units, with production-style four bolts per cylinder. Their cathedral-port, 15-degree design have 235cc intake runners and flow very well out of the box, but they really responded to the port work conducted by Jim Kuntz.
Kuntz may be an unfamiliar name to Chevy engine builders, but he's a whiz, and Ford heads and World Products turned to him because LS heads are essentially mirrored versions of the Ford Windsor-style head-only the valves are oppositely positioned.
A standard small-block crankshaft...
A standard small-block crankshaft is used without modification. In the case of this first Motown LS build-up, it's a 4.00-inch stroke that will complement 4.125-inch bores to deliver a 427-cubic-inch displacement. The reduced windage of the small-block block design over the LS deep-skirt block frees up horsepower, enhancing the output of the Motown LS.
Just as important to the engine is the unique valley cover that mounts the top of the heads. It's when the heads are bolted onto the small-block and valley cover that the picture of something truly unique comes into focus.
The remainder of the assembly process is pretty much like buttoning up a standard LS or small-block. A regular LS intake manifold bolts right up and a standard small-block distributor simply drops through the valley cover. You could even install electronic fuel injection if you wanted.
The spark plug wires are not conventional, however. Because of the differences in spark plug locations between LS and small-block heads, standard small-block wires don't quite fit. And, of course, the distributorless LS ignition system uses very short leads between the coil packs and plugs, so cut-to-fit universal wires are required.
Off-the-shelf forged aluminum...
Off-the-shelf forged aluminum LS pistons for the 4.125-inch bores are used with LS-type metric rings. There's nothing trick about them-just more off-the-shelf parts for this unique engine. Compression is a pump gas-compatible 10.7:1.
By the way, the Motown LS uses the LS-style firing order of 1-8-7-2-6-5-4-3.
Dyno Validation
Along with documenting the assembly of the Motown LS, we hung out at World's shop long enough to watch it fire to life and undergo its first test session on the dyno.
After a brief warm-up/break-in period, the engine produced an eye-opening 629-horsepower/579-lb-ft. result. That's about 70 hp more than one of World's regular Motown small-block 427 engines, and about 15 horses more than their typical Warhawk LS combos.
The significant jump in power over a conventional small-block didn't surprise anyone, but the degree to which it over-performed did.
Standard small-block connecting...
Standard small-block connecting rods are used. Not even the small end has to be machined for the LS pistons, as the pin diameter is the same.
"We were really pleased with it," says Mitchell. "It validates our idea and proves the airflow of LS heads is superior."
But what about the power increase over World's own LS engine? It wasn't all due to a simple port job on the heads. Mitchell then reminded us of the differences between the small-block and LS cylinder block designs. The LS block has a deep skirt design (also known as a "Y" block), while the small-block casting extends only to the crankshaft centerline.
The LS block design enhances overall rigidity, which is particularly helpful with the aluminum castings of automotive production applications, but it creates considerably more crankcase windage than the small-block. The Motown II block is plenty stiff to begin with, with thicker-than-stock key features (bullheads, "China" walls, etc.) and four-bolt mains.
"Windage makes a huge difference," says Mitchell. "With this combination, you've really got this best of both worlds-an affordable, performance-oriented bottom end, and the great breathing of LS heads."
The implications for the Motown LS are far-reaching, particularly for rodders who want a maximum-power street engine that slips into a small-block-prepped chassis (it weighs about the same as one of World's Motown small-blocks with aluminum heads). And in the unspoken game of "you ain't got nothing like this" that plays out at shows and cruises, it is definitely an engine that will draw attention.
More inexpensive, standard...
More inexpensive, standard small-block parts on the bottom end include the oil pump and pick-up. Because an off-the-shelf crankshaft and oil pan are used, nothing exotic is required for their complementing parts.
Whether OEM or aftermarket,...
Whether OEM or aftermarket, the oil pan for the Motown LS engine is a standard small-block size and fit. This significantly lowers the cost, as the aluminum structural pans for LS engines are expensive off the shelf and even more so if a custom unit is required for installation in a street rod.
Here are the LS lifters being...
Here are the LS lifters being lowered into the block small-block-style, rather than the pocketed design of an LS engine. The block was designed for the LS lifters; this wouldn't work on a standard small-block.
Here's the distributor mounting...
Here's the distributor mounting pad on the rear of the engine's unique valley cover. It locks the distributor in place like the provision in the original small-block.
This unique valley cover plate...
This unique valley cover plate is one of the key components of the Motown LS assembly. It secures the upper portion of the heads and because an LS-type spider intake is used, provides a mounting location for the distributor. Also: the valley cover has a removable top section that allows easy access to the lifters.
Here's World's Warhawk LS-1...
Here's World's Warhawk LS-1 heads being installed on the small-block. Port work was handled by Jim Kuntz, who's a whiz with Ford Windsor-style heads, which are similar to the LS design. The heads are bolted to the decks and unique valley cover.
Here's the basic long-block...
Here's the basic long-block assembly. Production LS valvetrain components, including the rocker arms, springs, etc. are used, but the combination requires custom 8.200-inch pushrods because of the non-LS camshaft position.
Like the original small-block...
Like the original small-block engine, the Motown LS block includes a provision for a mechanical fuel pump, just perfect when building a carbureted engine.
This mock-up photo shows the...
This mock-up photo shows the distributor mounted on the Motown LS engine, secured via the custom valley cover.
The Motown II LS deck height...
The Motown II LS deck height is raised to the LS-production spec of 9.240 inches, so any LS intake will bolt right up. In this case, it's an Edelbrock intake capped with a velocity-enhancing spacer and an AED-built 1050 Dominator.
The other unique parts created...
The other unique parts created for the Motown LS include adapter plates for the front of the heads to mount a water pump and other accessories. A crossover tube is used to connect the small-block's standard water pump inlet and outlet ports, so the water flow will correspond with the LS circuit. (Disregard the Mo-hawk name milled into the plate. It was an early nickname that didn't make it past the copyright lawyers.)
Here's the finished assembly....
Here's the finished assembly. Just like a regular small-block, the distributor slips in at the rear. The only problem is plug wires. Standard small-block wires don't fit quite right, so a cut-to-fit kit is necessary. On this engine an electronic MSD distributor provides the spark.
On the left is one of World's...
On the left is one of World's Warhawk LS engine assemblies and on the right is the Motown LS. The greater deck height makes the Motown LS taller and, at the top, wider than a conventional small block, but the front-to-rear length is essentially unchanged from a conventional small-block.
With minimal tuning and 36...
With minimal tuning and 36 degrees of total timing, the Motown LS engine cranked out 629 hp and 579 lb.-ft. on the first try. That's about 70 horses more than a comparable World Products small-block and about 15 more than one of their LS crate engines.