World Products' Motown LS Engine- Something Old And Something New

To adapt the LS heads, World redesigned the small-block's water jackets to match the LS design. They also raised the deck height to the LS production height of 9.240 inches-enabling standard LS intakes to bolt on without a hitch-and redesigned the block's valley to accommodate LS lifters.

But just as remarkable about this engine's combination is all that's usable in off-the-shelf parts from either a small-block or LS, including:
* Standard small-block crankshaft
* Standard small-block connecting rods
* Standard small-block distributor and timing gear
* Standard LS pistons (pinned to the SB rods without modification)
* LS hydraulic roller lifters
* LS valve springs and rocker arms

Of course, there are some unique pieces that make this combination work. They include:* A camshaft with LS lobes, but small-block-specific fuel pump lobe and rear distributor drive gear
* Top-of-engine valley cover plate that mounts the top of the heads and the distributor
* Custom-length, 8.200-inch pushrods
* Adapter plates that bolt to the front of the heads for production-style accessories and water pump mounting

In our story, we've outlined not only the components that distinguish the Motown LS, but follow along as they create a 427-cubic-inch crate engine that delivers more than 600 naturally aspirated, fully streetable horsepower.

Block And Cam Details
Examine the accompanying comparison photos closely and you'll see the obvious differences between the Motown LS and a conventional small-block. The most notable are the decks, which look like LS decks.

The block also incorporates important oiling circuit changes that World also bakes into its new Motown II casting-their "standard" small-block. Those changes include a redesigned, priority-main feed system; relocated cam journal oiling holes from the 6 o'clock position to a 5 o'clock position; and oil restrictors moved to the middle of the lifter valley.

Advantages of the changes include:
* Camshaft oiling that is not affected by high valve spring pressure
* The distributor is fed at the end of the oiling cycle, reducing the chance of oil pressure loss through distributor O-ring leakage
* The relocated oil restrictors can be changed without removing the transmission, converter or clutch

Also integrated are front and rear bosses to support a dry-sump oiling system. In fact, the oil circuit changes are worthy of a story in their own right; in this case, they happen to be part of an overall package that is noteworthy on every front.

The Motown II/Motown LS block is designed to accept the larger, 55mm cam size of the LS. However, because of the large, 4.000-inch stroke, a smaller-diameter cam was needed on the engine depicted in our story. World called on Comp Cams to build a standard small-block-sized cam with LS lobes, a small-block fuel pump lobe and distributor gear.

As for the cam's specs, it delivers about 0.650-inch lift on the intake side and 0.660-inch on the exhaust side, with duration of 250/255 degrees. With the high-flow, World-manufactured Warhawk LS heads and the engine's large displacement, a big cam was absolutely required.

With the camshaft and heads in place, the rest of the engine combination falls together quite easily. The Motown LS block is designed to use LS lifters, which slip into the block small-block-style rather than the pocketed style of production LS engines.

Because the camshaft is lower in the small-block than an LS engine, and the deck is significantly higher than a regular small-block, neither regular-length LS pushrods nor small-block pushrods are usable. The Motown LS uses 8.200-inch-long pushrods. Stock small-block length is about 7.800-inches, while stock LS pushrods are about 7.400-inches long.