Junkyard 5.3-liter engines have always been popular. The iron-block variants are (or were, anyway) cheap and plentiful in junkyards, and you didn’t have to worry about the condition of the cylinders, because there was enough meat to go way more than .060-inch overbore. Gen-III and Gen-IV 5.3-iron blocks were easily punched out to the factory LS1 bore size of 3.898 inches — a whopping 0.118 inch larger than they cam from the factory. That allowed for common, off-the-shelf performance parts to be used to put together a solid 5.7-liter factory-crank combination that could take pretty much anything you could throw at it up to four-digits-worth of horsepower. 454 cubic-inches, though? Yeah, right.
However, even with a common 4.00-inch stroker crank in them with the “big” 3.905-inch LS1 pistons, you were still only in the 383 cubic-inch range. Not exactly the mountain of displacement a lot of people want. However, Tommy Keeter of BoostLine Performance recently debuted what they are calling the 454 Evolution. After months of working on a cylinder sleeve program, Keeter has been able to reliably take a 5.3-liter iron block, and open it up to 4.185 inches of bore size. A whopping .280 inch more bore than the 5.3s traditional maximum bore.
While it might seem impossible, Keeter has worked out a combination of sleeves and installtion process that allows him to create a 454 cubic-inch combination from a simple iron 5.3-liter truck engine block.
454 From 5.3… How?
Taking a 5.3-liter block and getting a whopping 7.44 liters out of it might sound impossible, but it’s not. Starting with a run-of-the-mill 5.3-liter truck block, Keeter machines out the cylinders to accept the stepped cylinder liners he’s worked hard on perfecting. The wet sleeves are stepped in order to eliminate any chance of them dropping once locked into place. That’s not quite the end of the machine work on the block, as Keeter then clearances the new sleeves for a massive 4.125-inch-stroke crankshaft.
That’s not something you see in a 5.3-liter block, because typically, that makes the engine massively undersquare. However, with the new, huge bore, this new 454 Evolution design remains oversquare by .050 inch. While this all sounds good on paper, I’m sure there are a lot of you who, at this point, are thinking that just because you can fit the components, it doesn’t mean they will actually work together. Well, Keeter thinks that way, too. So, to prove his point, he put together a killer combination to run on the dyno.
Starting with his 454 Evolution block, he took a forged 4.125-inch-stroke crankshaft and dropped it in the mains with Clevite bearings and secured it with ARP main studs. He then hung a set of 6.125-inch forged H-beam connecting rods off the rod pins, again with Clevite bearings and secured with ARP rod bolts. He connected those to a set of short (you can do the math on the compression height needed for this combo) forged 2618 flat-top pistons, and voila! A 454-cube short-block. Keeter added a Melling high-volume oil pump and GM Performance’s “Muscle Car” oil pan to handle the oiling duties.
A Monster Top End
Topping off the beastly short-block are a set of Frankenstein Engine Dynamics M712 cylinder heads. These LS7-based cylinder heads are no joke, with CNC-machined 283cc intake ports, 95cc exhaust ports, and a 64.5cc chamber. In the chambers are 2.205-inch intake valves and 1.614-inch exhaust valves. On the flow bench, they move 395 cfm at .800 inch of lift and 383 at a more reasonable .600 inch of lift. The heads are secured with Cometic MLX head gaskets and an ARP head stud kit.
For the valvetrain, Keeter doesn’t divulge too many specs, other than revealing the cam is an off-the-shelf BTR grind, along with LS7 lifters and trays, a billet double-roller timing set, and a timing chain dampener. The rocker arms are traditional LS rocker arms upgraded with a bronze-bushing trunnion kit, and they are actuated by upgraded 3/8-inch pushrods.
Feeding the monster naturally aspirated combination is a F.A.S.T. 103mm LSXHR intake manifold. The composite tunnel-ram-style intake manifold excels in the high-RPM, high-airflow arena, and is a perfect choice to be paired with the 103mm drive-by-wire throttle body.
As configured, the test engine is a beast. However, there is definitely room for improvement, by switching to a few custom components instead of all off-the-shelf parts, as you see here.
454 Cubic-Inch 5.3 On The Dyno
Keeter wasn’t looking to pussyfoot around on the dyno trying to keep the engine alive. Rather, he gave it all the beans and beat on it, hoping to prove the combination’s durability and performance. And that he did. After the dyno session was completed, not only was the engine happy as a clam, but it also posted some killer numbers.
Keeter pulled the engine to 7,500 rpm in a 3,000-rpm sweep. Peak torque arrived at 5,300, while peak horsepower came in at 7,200 rpm. Those numbers were 836.8 horsepower and 707.1 lb-ft of torque, with curves that will blow the tires off whenever you want. That makes this engine a solid 1.84 horsepower per cubic-inch combination, with room to grow on the induction and valvetrain side. No small feat for a big-block-sized LS engine.
836.8 horsepower at 7,200 rpm and 707 lb-ft of torque at 5,300 rpm. No matter how you slice it, those are big numbers, naturally aspirated or otherwise. On the right, you can see the power curves of the engine, which will absolutely roast the tires at any RPM.
