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Gen III/IV Small Block Engines - Big Displacement Gen III/IV Engines

Stroker Motors Are What Everybody's Hot For These Days, And That Includes Building...

Photography by Dale Schwartz, , JE Pistons

When it comes to car crafting, it's all about horsepower. The latest darling for the GM devotees of more power is the newest generation of small-block engines, more accurately termed Gen III and Gen IV. These new-millennium small-blocks are quickly becoming a favorite engine swap powerplant. For those willing to spend a little coin on building something a little more exotic, there are plenty of opportunities to expand the stock bore and stroke combinations for more displacement. If you've got deeper pockets, the LS2 and LS3 engines offer larger bores right out of the box, combined with an enticing all-aluminum structure. Or you can pony up for an iron block from GM Performance Parts, aluminum World Products Warhawk block, or a CNC billet Dart piece. Whichever way, you have the foundation for big inches.

Of course, for those of us who aren't on the board of directors of an oil company, there's also the classic route using a stroker crank in a stock production block. This is an outstanding approach that combines power with a more conservative financial investment, and it seems the aftermarket crank companies aren't shy about offering some really outrageous strokes. There are land mines you really should look out for, too, and we know where most of them are. So tag along on our stroked and bored journey through the Gen III/IV maze and see what floats your horsepower boat.

Block Basics
Power is all about breathing, especially if you are planning to build a big displacement engine. One of the main limitations on the early LS1/LS6 engines is the 3.898-inch bore and the rather thin iron liners that limit enlarging the bores more than 0.010 inch. That quest for more power and better breathing from very good production heads is what drove GM to the Gen IV LS2/LS3/L92 engines that now sport wider 4.00- or 4.060-inch bores. Not only does the larger bore improve breathing, but the greater diameter also allows larger intake valves. The now-famous L92 truck heads come right from the factory with massive 2.16/1.59-inch valves. But remember, these rotund valves will not fit in any bore smaller than 4.00 inches.

Of course, aluminum blocks are also prized for their reduced weight. A stock LS1 aluminum block barely registers at 110 pounds, while iron blocks push that figure to a more robust 175 pounds. The incentive to side with iron is increased strength, more bore size options, and a budget price. Even as thin-wall castings, all iron blocks can be bored 0.030 inch to help boost the displacement. If you want to really step up in durability, the GM Performance Parts LSX iron block is among the sturdiest, as revealed in its bare casting weight of a rugged 225 pounds or about 50 pounds heavier than a production iron block. In theory, there is enough room to stuff a 4.250-inch stroke crank in the LSX block, but this also means that with a 6.125-inch rod, the piston's compression height would only be 0.990 inch and the piston skirt would extend another 0.125 inch out of the bottom of the bore compared with a 4.00-inch stroke crank. No engine builder we talked to was comfortable with that.

If you're into really large inches, there's the World Products Warhawk aluminum block that specs in at 133 pounds with caps and iron sleeves. With a 9.240-inch deck height, it can accommodate up to a 4.00-inch stroke and a 4.155-inch bore, which will create 434 ci. If you want more, World also has a tall-deck Warhawk block with a deck of 9.800 inches that can be morphed into a monstrous 481ci using a long-armed 4.500-inch stroke and 4.125-inch bore.

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