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Super-Sized Big-Block

World Products 632-Cube Crate Engine Redefines the Adage, "There's No Replacement for Displacement"

Sep 24, 2004

Many health officials have decried a generation of super-sized food and beverage portions as one of primary factors for America's obesity problem. Film director Morgan Spurlock examined this in his recent film, Super-size Me, in which the sort-of documentary followed him as he ate nothing but fast food for 30 days straight.

Of course, food isn't the only super-size product Americans consume; for good or bad, it's part of our culture and has been for decades. In the auto world, super-sizing started in the early '60s with the advent of the big-block V-8. And like today's fountain drinks at the corner convenience store, they seemed to grow larger with every year.

Back in the day, Corvettes could be had with big-block V-8 engines displacing 396, 427, and even 454 cubic inches. And while the horsepower generated by these iron giants--and in two production instances, all-aluminum--was admirable, their real strength lied in tugboat-like torque.

Chevrolet quit super-sizing Corvette engines after the '74 model year, but the abundance of current crate engine packages, including GM Performance's own 427 ZL-1 re-issue and recent 572 offering, shows there's still great interest from enthusiasts who crave the pull only a Mark IV-style rat engine supplies.

World Products is in the super-size game, too. The company's line of big-block Chevy-style Merlin engines has worn size "XL" tags for years. Now, however, World Products has dropped all pretense of building simply a larger-displacement big-block crate engine; they've developed the Monster Merlin of almost unfathomable dimensions--632 cubic inches.

That's right, 632 cubic inches of cylinder displacement (that's more than 10 liters to our metric readers). What's even more amazing is that, from its outward appearance, the 632 looks just like any other big-block Chevy engine. It takes up no more room than a GM-built rat, too--meaning it'll fit wherever a 396 or 454 will. Think of it as stuffing the contents of an entire french-fry basket into the standard-size bag.

How's this possible? Well, World Products' Merlin big-blocks (and MoTown small-blocks) are based on the external dimensions of GM's engines, right down to the last bolt hole. So from the outside, there's no discernable difference. Inside the engine, however, World Products casts the blocks and cylinder heads with more material. This strengthens the blocks, which not only supports big horsepower numbers, but allows World to bore and stroke the heck out of 'em.

That seemingly simple recipe helped create the 632, which has truly monstrous 4.600-inch bores and a lonnngggg 4.750-inch stroke; a Chevy 454 engine has "only" 4.250-inch bores and a 4.000-inch stroke. Equally super-sized are the aluminum cylinder heads' 350cc ports and 2.30/1.88 valves, which are necessary to support the airflow needed to produce the engine's pump-gas-rated 780 horsepower and 815 lb-ft of torque. (The engine also is available with iron heads.)

We wouldn't be surprised if the 632 made 800 horses or better as our experience with World Products' engines has shown they typically under-promise and over-deliver. It's a way, we're told, to ensure no customer will feel short-changed on the dyno--whether they live in the thick atmosphere of the South or the thin air of the Rockies.

Along with the super-sized reciprocating assembly and cylinder heads, the rest of the 632's specs are pretty straightforward: a single-plane intake manifold and a modified Dominator-type four-barrel carb; a COMP Cams roller camshaft; roller lifters; and a HEI-style distributor and 8mm plug wires. It is nothing exotic, just "off-the-shelf" components that have been tested time and again to work in harmony.

And while the Monster Merlin will bolt into your vintage Vette without any trouble, it'll require some super-sized planning; dropping an engine producing more than 800 lb-ft into an otherwise stock chassis is pretty much like swapping a dogsled team with a half-dozen moose. A super-size rearend, bullet-proof transmission, and a heavy-duty cooling system are musts before setting your cul-de-sac a tremble.

Frankly, the 632 will make your checkbook or credit card tremble, too. The price for the 780-horse, aluminum-headed Monster Merlin we've outlined in this story is--sit down for this--$16,495. You can save $1,500 bucks by opting for the iron-head version, but it will weigh more and make less power.

No, the Monster Merlin is not for the faint of heart or faint of credit balance. But if you're looking for the ultimate streetable big-block for your Vette, it's hard to argue with the earth-mover-like torque cranked out by this gargantuan-displacement 632. It's a big-block that doesn't say no to bread.


The starting point of World Products' large-cube madness starts with the company's own Merlin iron-block casting. Although externally identical to a big-block Chevy, including every bolt hole and accessory mounting pad, it carries more material inside the block. The bulkheads are thicker, for example, as are the cylinder walls.

For the 632-inch engine, the Merlin block is bored out to 4.600 inches. The extra iron cast into the block makes the super-wide bores possible while still facilitating adequate cooling and wall strength.

Complementing the 4.600-inch bores is a 4340 forged-steel crankshaft. It provides an extra-long, power-building 4.750-inch stroke.

Four-bolt main caps are standard, and the caps can be had in either nodular iron or billet steel.

The camshaft is a roller type from COMP Cams, but not surprisingly, World Products was a little coy about its specs. Suffice it to say, the cam provides a strong lope, but it still delivers great idle quality and low-rpm responsiveness.

A high-volume oil pump is included--a must for the lubrication needs of this on-the-edge big-block.

The pistons are forged aluminum parts that deliver an approximately 10.4:1 compression ratio. They're pinned to Eagle 4340 forged aluminum rods that are 6.700 inches long.

The 632 is available in versions with iron or aluminum heads. The alloy heads (seen here) carry a premium of about $1,500 on a complete engine, but they're worth more power and weigh about 50 pounds less than their iron counterparts. The aluminum heads boast 350cc intake runners.

CNC-machined combustion chambers in the aluminum heads have "fast burn-style" designs. Like everything else in the engine, the valves are big, too--2.30 inches and 1.88 inches. (And you thought 2.02/1.60 valves were big!)

Backing up valves is a set of roller-tip lifters. They actuate a set of Manley 4130 pushrods.

On top of the heads is a set of Harland Sharp 1.7-ratio roller rockers and a stiff set of valve springs.

With the engine's capability to push a large quantity of air, it needs to draw a large quantity of air. That chore falls to a modified Holley 1050 Dominator and World Products' own high-velocity, single-plane intake manifold.

Some of the 632's standard accessories include a complete HEI ignition (with 8mm wires) and an internally balanced SFI balancer.

Production versions of the 632 will vary visually from our buildup version, including snazzier valve covers and oil pan. But, in a nutshell, this is how the 632 is delivered--plugs, wires, and carburetor installed. And with its nearly exact dimensions to a standard Chevy big-block, it'll drop down into any big-block-capable Corvette chassis, and then its Viper-hunting time.

Every World Products crate engine is dyno tested and tuned prior to shipment, so the dynamometer workout of our project engine was just part of the routine. Not surprisingly, the engine made a little more than the claimed 780hp and 815 lb-ft of torque. That's typical for World Products' engines, as we find the company tends to under-promise and over-deliver. Beyond the power numbers, though, is the fact that this ultimate big-block has great idle quality and is very tractable for a street engine.

The Diet Small-Block

0411vet_wp632_17_z 18/18

World Products MoTown "Lite" small-block casting weighs about 100 pounds less than an iron version and has several interesting new design features, including cross-valley ribs that add strength and provide passages for a crossover oiling system. There are horizontal reinforcing ribs on the outside of the block, too.

So, you're doing the Atkins thing, huh? Super-size fries and a two-liter of soda off your list? Well, the wannabe-slimmer you might just be looking for a lightweight alternative under the hood. So, instead of the huge Monster Merlin, try the comparatively featherweight all-aluminum MoTown small-block. World Products started producing them a few months ago and offers everything from a bare block to a built 415-cube crate engine rated at 450 horsepower.

0411vet_wp632_18_z 19/18

Like World Products' iron block castings, the aluminum MoTown small-block has more "meat" around the cylinders. The cylinder liners allow (at this writing) a maximum of 415 cubic inches.

Weighing about 100 pounds less than a comparable iron small-block, the MoTown offers a respectable weight savings from the nose of any Corvette.

Lay off the Big Macs for a few months, and you and aluminum-motored Vette might just float away.




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