There’s no doubt that the Gen IV LS is stronger than the Gen III. With better rods and pistons, it seems to be the go-to combination for guys wanting to throw some power at a stock bottom end. In fact, we know some people that refuse to use stock Gen III components. So the question is, how much power can a stock bottom-end Gen III 5.3 take?
Here are some things to note about this test. Richard Holdener, the guy in the video, made some changes to the 250,000 5.3 LS before hitting the dyno. The reason he did this was to make sure that all of the problem areas would not be an issue during the dyno. Holdener opened up the ring gap to ensure the cast pistons would not suffer ring land damage with the extra heat generated by the combination. While nothing in the video mentions upgrading the head gaskets or bolts, we are willing to bet that the torque to yield bolt was swapped out for head studs or at least aftermarket head bolts. Holder mentions that he made sure the head gaskets were sealing but didn’t go into any details.
So what’s the purpose of this “big bang” test? Holdener wanted to see what horsepower the stock Gen III crankshaft, rods, and pistons could make. Before we get into the dyno, we should note that this engine had an excellent tune, good fuel, air-to-water intercooler, Trickflow heads, COMP cam, twin 76mm turbos, and FAST intake manifold.
In naturally aspirated form, the little Gen III 5.3 made an impressive 503 horsepower and 442 lb-ft of torque. Holdener then removed the long tube headers and replaced them with a set of twin 76mm turbos. At only 5.5-pounds of boost, the 5.3 laid down 697 horsepower and 606 lb-ft of torque. When upped to 15.5-pounds, the mill produced 1,015-horsepower and 872 lb-ft of torque. Surely these power figures were close to breaking the Gen III internals. Nope. Holdener made pulls all the way through 24-pounds of boost where the engine produced 1,305 horsepower and 1,106 lb-ft of torque before calling it quits.
In the video Holdener says that he wishes he would have spun the engine up to a higher RPM, and we agree. It would have been interesting to see if the internal components would have lived north of 6,300 RPM and what kind of power it could have produced. However, even with the current test, we have a new appreciation of what a Gen III rotating assembly can take, despite what the internet may tell us.