We're used to the unexpected from World Products--things like 454-cube small-blocks and big-blocks with cylinders large enough to warrant their own ZIP codes. But this is something altogether new and unprecedented--a traditional small-block-based engine topped off with LS cylinder heads.
Can't be done, you say? If you were to try such a combination with a standard GM small-block or even one of World's regular Motown small-block castings, you'd be right.
The first piece of the Motown...
The first piece of the Motown LS puzzle is World Products' redesigned cylinder block, which adapts LS heads via the water passages and bolt pattern. The decks are raised to the LS-production spec of 9.240 inches, so any LS intake will bolt right up.
But World has gone and mixed with the natural order of the universe and redesigned the small-block to not only accept the LS head's bolt pattern, but match its water passage design. The result is a small-block on the outside that incorporates LS compatibility where it counts.
They call it the Motown LS. If your head is still swimming about this, consider the reasons for engineering such a hybrid:
* It allows the small-block to produce new, extreme levels of Streetable power that were almost unattainable with traditional small-block heads
* It offers a tremendous performance advantage to racing classes that demand a distributor-triggered ignition system
* Installation in older cars and race cars is a snap because the small-block oil pan and motormounts are unchanged
This close-up shot illustrates...
This close-up shot illustrates the water passage and head bolt designs that were transferred to the small-block architecture. It uses four head bolts per cylinder, like a production LS engine. The redesigned water passage was a big deal, because the small-block feeds coolant into the block first, while the LS pushes it through the heads first.
"As much as the small-block and LS are different, there are some key similarities that make it work," he says. "It's clear when you examine the LS engine that there is a direct path back to the SB2 engine--an extension of the small-block design."
Among the key enablers of this small-block/LS hybrid is one of the very details that GM instilled with the LS architecture: the small-block's 4.40-inch bore centers. That means the heads' combustion chambers are located perfectly above the bores.
Also, an LS-style camshaft fits inside the small-block cam holes. All that's needed is a distributor drive gear on the back of it and fuel pump lobe on the front. (World got Comp Cams to build one for the engine seen in this story.)
Surprisingly, what's remarkable about the Motown LS isn't what's new about the engine, but what is carried over from one engine or the other. That includes:
The block also incorporates...
The block also incorporates the oiling system changes of World's "regular" Motown II block, meaning the oil restrictors are moved from the rear of the block to the valley for easier access. The cam journal oil holes are also relocated to ensure adequate flow with a high spring pressure.
* 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 z rocker arms
And because World casts the Motown LS block with the standard LS deck height of 9.240 inches, off-the-shelf LS intake manifolds bolt on without a hitch. There are some unique pieces that make this combination work, of course. 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