As you may faintly remember from biology class, evolution is a change in the inherited traits from one generation to the next. In the automotive ecosystem, designs evolve the same way living things do, with only the fittest designs withstanding the test of time. The Chevy V8 evolved all the way from the original 265 cubic inch small block in your grandpa’s Corvette to the powerful LS7 that powers that same car today. But evolution doesn’t always follow a straight path, and crossbreeding between branches of the same line and the resulting “hybrid vigor” can lead to offspring with all the strengths of the parents, with few of the weaknesses. A perfect example is World Products’ new Mowtown LS block, which combines the time-tested design of the traditional small block Chevy with the ability to bolt on a set of high flowing LS heads. The result is an engine that’s less expensive to build than a LS-block mill thanks to its SBC heritage, but still bolts right up underneath deep-breathing LS heads and intakes.
What this means is that World was able to take their extensive knowledge learned over the years from racing and building high performance small blocks and combine it with the unlimited potential of LS engines. We recently had the chance to speak with Bill Mitchell Jr. of World Products to get the details on this revolutionary block.
The Motown LS block uses World’s new Motown II small block Chevy design as its foundation. “We wanted to give guys a third option for their Chevy small block instead of just the traditional or the LS series,” said Mitchell. “Think of this block more as a middle ground for guys wanting more power, but not wanting to part with their distributor-based ignition system.” It also provides a lower-cost way to taking advantage of the LS high-flowing heads, and a lighter one as well. According to World, the Motown LS weighs 75 pounds less than an OEM LS iron block. The bottom half of this block is identical to World’s latest standard small block Chevy offering, the Motown II, and like its sibling, the Motown LS features many design changes compared to the older Motown block.
The biggest change has to be the redesigning of the oiling circuit. World decided that changing the oiling system to a ‘priority main’ design would be the best way to go with for the next generation block. What this means is the distributor is now at the end of the oil’s path through the block, and World points to the fact that the leaking problems often plaguing older small blocks when the distributor was improperly fitted or the o-rings were damaged will be eliminated through this change.
The oil restrictors were relocated from the rear of the block into the middle of the lifter valley, making then a hell of a lot easier to access, as well as equalizing oil pressure. An added benefit is that there will be no more removing your transmission just to change out the oil restrictors.
The oiling changes can also be seen upon a closer inspection of the cam journals. In the world of high performance engine building, camshafts requiring high spring pressure are not uncommon. Some builders have reported problems when that camshaft is pushed down, covering or partially blocking the oiling hole located in the 6 o’clock position of the journal. To solve this, World moved the oiling hole from its 6 o’clock position to a 5 o’clock position.
While the bottom of this ground-breaking block may be a traditional small block design, the top is all LS. In doing so, World had to reconcile the ‘block feed first’ cooling system design of the older small block with the newer ‘head feed first’ design of the LS series engines. The Motown LS stays with the SBC water path, with an adaptor to return coolant from the heads to the radiator, and has expanded water jackets that hold 152 fluid ounces per side, or almost a half-gallon more than an OEM block for improved cooling capacity. With the water issue settled, World decided to go with the LS-style four-bolts per cylinder head bolt pattern. “We thought that going with the 6-bolt style might leave the block a little weak,” said Mitchell, “so we decided to just stay with the 4-bolt style for more support.” While this might be an issue for a racer looking to add high amount of boost, the rest of us should be fine. A good rule of thumb is if an LS block can handle it, this block will too.
The LS series engines have a deck height of 9.240 inches compared to the 9.025 inch deck height of the customary small block Chevy, so World had to be creative when it came to mounting the larger LS heads on the small block. The solution was to use the deck height of the LS engine and add a valley cover plate that would provide the finial mounting points for the top bolts of the heads, making installation of a set of LS heads on this block exactly the same as on an LS block. Besides holding on the heads, this also provides a spot on the engine to mount the distributor, an important piece not found on an LS engine. World even added a removable cover plate that gives you easy access to the lifters.
Here you can see how the top bolts on the LS heads bolt to the valley cover plate.
Speaking of lifters, this engine is designed to use LS lifters as well as a number of other off-the-shelf components. In fact, when it comes to things like the intake, pistons, and rods, they are all commonly-available parts. But are they small block or LS parts, you ask? “Most of the internals are small block Chevy parts, but for things like pistons and lifters, we had to go with the LS style,” Mitchell explained.
The Bottom End
The lower half of the block mimics the design of a traditional small block Chevy, so it comes as no surprise that most of the components that fit inside the Motown LS are small block parts. That means if you are heavily invested in the SBC, you have most of what you need to build an engine based off this block, starting with the oil pan. While what type of oil pan bolts under the block might not seem like a huge deal, it makes getting the completed engine into the car a breeze. Especially when you consider that World was clever enough to cast the Motown LS block with both the traditional small block engine mounts as well as the LS style mounts, making the installation of this block simple no mater what you are putting it in.
Another advantage of the small block bottom end is better control of oil in the crankcase. While LS engines do not necessarily have bad oil splash control, the traditional small block’s design just does a better job at keeping the oil where it needs to be – off the crankshaft, which frees up power by reducing windage.
Moving up from there, the block is designed to accept many small block Chevy crankshafts, leaving you almost endless combos of cubic inches. “The internals of the bottom of the block are the same as a small block,” said Mitchell. “Anyone familiar with small block Chevys will be able to see that.” Small block rods are also used for this configuration. Up to this point, the build of an engine using World’s new Motown LS is no different than a standard small block. That all changes when the pistons come into play.
The only pistons that will play nicely with LS heads bolted to the top are LS-type pistons, and the LS-sourced parts list starts with a set of slugs. World found that LS pistons bolt right on to the SBC’s piston rods with no problem at all, and the metric piston rings even seem to work extremely well in the SBC-style cylinder bores.
Moving on up, as mentioned before the lifters are a direct swap from an LS engine. World did their homework when coming up with the design for fitting these lifters in the block – don’t try this with your SBC. Obviously, heads are LS-spec, and because World went with the LS deck height, any LS-style intake will bolt right up, giving the engine builder almost endless options of intake and head combos.
The Motown LS block uses stock LS-spec lifters, but requires a custom pushrod length due to the position of the camshaft in the block, relative to the deck height.
Passing Out The Sparks
Ignition is handled by a small block distributor that can be installed in the traditional sense thanks to the valley cover plate at the top of the block. While this might not seem like a big deal, it is if you plan to use your the block as the foundation for a race engine. Some classes require that you run a distributor, which in the past was an easy way to limit racers to traditional small blocks including their heads and intakes. This is not the case any more, so if you are not limited by rules limiting the heads or intake you use, this would be an excellent way bring a set of high flowing LS heads into your racing class. So when do things get interesting? Where are the custom parts? There are a few custom parts that you will need, but most of them you can get right from World Products.
Making It All Work
Only a few items on the parts list have to be custom ordered, starting with the valvetrain. As mentioned before, the deck height of a block determines a lot of things including the pushrod size. World Products keep the camshaft in the small block location, but because the deck was raised they were unable to source stock pushrods from either the LS engine, which uses a 7.400-inch pushrod, or the small block that uses a 7.800-inch pushrod. The solution was an 8.200-inch push rod.
The camshaft is another piece that need to be custom made. Not a big deal, as companies like COMP Cams, who World used to build their custom stick when testing this engine, are able to custom-grind any camshaft you can think of. While you are going to need LS-positioned lobes to work the LS valvetrain, the reason you cannot use an LS cam is not because it won’t fit inside that block. An LS camshaft will slide right in a Motown LS block with no problem at all.
The valley cover plate with the top cover removed shows how it provides a spot for the distributor in the rear just like a small block Chevy.
The difficulty is because LS engines use a Coil-On-Plug (COP) ignition system, and their camshafts do not have a distributor gear. A custom cam with a distributor gear in the rear, just like a small block cam, is needed to spin the ignition. Also, if you’re using a mechanical fuel pump, you are going to need a small block fuel pump lobe on the front. This is all a little confusing at first, but just remember all you need is a camshaft with LS lobes with a small block fuel pump lobe and distributor gear. Speaking of ignition systems, because the distributor is mounted in the standard small block position, you are able to use a set of small block plug wires on this engine.
Finally the last two things that make this combo work are both supplied from World Products. As mentioned before, the valley cover plate provides a mounting point for the top bolts on the heads as well as a place to mount the distributor. What has not been covered is the adapter plate that mounts to the front of the heads. This simple-looking plate is one of the essential pieces that make this combo work. While it may look like all it does is provide a spot on the LS heads to mount a water pump and other accessories from the small block belt system, what you don’t see is how World used a crossover passage to connect the small block’s standard water pump inlet and outlet ports, so the water flow will work with the LS water circuit path.
These are the parts that make this setup work – the valley cover plate and the adapter plate that mount to the front of the heads.
Overall, this groundbreaking block could be a look into the future of Chevy small block performance. By combining the best of the old with the flow technology of today, World Products has made one of the most unique block designs seen in some time. The uses are endless and with both small block Chevy and LS style engine mounts, so are the applications. World is prepared to offer this block in everything from a bare block all the way to completed race-ready engines, but it all begins at the block. They are offering the block itself in two different part numbers with the only difference being the main caps. Part number 084080 comes with nodular iron splayed-bolt caps, while 084180 is equipped with billet splayed caps. No matter which one you go with, you are going to need the valley cover assembly to properly fit the heads to the block.
World Products Motown LS Block Specs:
• 9.24-inch Deck Height
• 8.437-inch Lifter Bores
• 4.000-inch Max Stroke
• 4.115-inch Bore
• 400-style Mains
• LS and Traditional Small Block Mounting Holes
Dyno Testing – Hardcore Drag Engine Rumors
According to World, the first engine they built was expected to make around 600 horsepower based on the parts and tune. To everyone’s surprise, including Bill Mitchell Sr., the engine made 629 horsepower at 6200 rpm and 579 lb-ft at 5100 rpm on the engine dyno. Not bad for an engine with a 40-year-old design heritage. World has been hard at work developing a combo that make the most power with this block including an all out hardcore drag example. World believes the no-joke drag motor will make well over 800 hp without running the engine anywhere near its breaking point. Look for these blocks to start tearing up the streets and strips soon.