Inside The Block
The key to making the hybrid engine work is World's Motown LS block, which is designed for the water flow characteristics and bolt pattern of the LS head. Check the accompanying comparison photos and you'll see the obvious differences: the deck of the Motown LS looks like an LS deck because of the water passages.
The block also incorporates important oiling circuit changes that World also bakes into its new Motown II casting--its "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.
World called Comp Cams to build a hybrid stick to match its hybrid engine. The details are, at first, a little confusing, so pay close attention: The Motown II/Motown LS block is designed to accept the larger, 55mm cam size of the LS, which seemed a natural for this engine. However, because of the large, 4.000-inch stroke, a smaller-diameter cam was needed, so Comp built a standard small-block-sized cam with LS lobe and small-block fuel pump lobe and distributor gear. Got it?
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 those high-flow heads and big, 427-inch engine displacement, a big cam was certainly needed.
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.
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.
Cylinder Heads & More
The heads used with the Motown LS block are World's Warhawk LS1 units (ported for the engine used in this story by noted Ford race engine builder Jim Kuntz). They bolt to the block in production LS fashion, meaning four bolts per cylinder. Although the Motown LS block has sturdy iron decks, the four-bolt pattern isn't the best for high-boost combinations. We'll just have to wait for World to make a block that supports its six-bolt LS7-X heads.
The cathedral-port, 15-degree Warhawk LS1 heads have 235cc intake runners and flow very well out of the box, but they really responded to the port work conducted by Kuntz.
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 unique comes into focus, something that has never before been built.
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 the small-block distributor simply drops through the valley cover.