Big Bang: Kick Starting The Turbo LS Revolution
The dyno test that started it all. The turbo LS that kicked of the modern horsepower wars and shocked all of us with its ability to not paint the dyno room walls with oil and pieces of the $500 stock bottom end LS: Big Bang.
It’s been roughly 15 years since the guys at Hot Rod magazine set out to see how far the LS can go without major short block upgrades under boost with Richard Holder and the team at Westech. But this turbo LS test isn’t some big public enlightenment on the performance potential with the LS platform. Everyone saw the potential starting back in the late 90s with the LS1s in the Corvettes and F-body Camaros and Firebirds with cam swaps, ported heads, and those who treaded into the unknown with supercharger kits.
The Sacrificial Stock Bottom End
The dyno mule was a junkyard-bought iron block small-displacement truck Gen-III LS with high mileage that to this day are still dirt cheap for anyone to get their hands on. The bottom end was torn apart to be inspected and other than some surface rust on a few cylinders, it was thrown back together with all stock parts including crank, rods, pistons, main cap and connection rod hardware, bearings, and rings. The cylinders were given a quick rehone with a dingle-ball hone to clean them up (one cylinder still had light rust damage that couldn’t clean up with the hone) and the rings were gapped to 0.028-0.030 inch.
The Perfect Topping
While the bottom end stayed stock, the heads and valvetrain needed some treatment to meet the lofty horsepower goals with boost. The stock heads received CNC porting from TEA with larger valves and dual valve springs and were bolted to the block with Fel-Pro MLS head gaskets and ARP studs. For the cam they went with a Comp XR281HR cam that specs out at 228/230 duration, 0.571/0.573 lift, and 112 LSA. The cam was run with a new set of Comp hydraulic roller lifters the stock pushrods and rockers we retained.
To finish the turbo LS off, a FAST LSXR intake, 75 lb/hr injectors, and matching 102mm throttle-body sits on top. The pair of 76mm turbos was combined with a twin-core, air-to-water intercooler, a pair of 45mm Hyper-Gates, and a single RacePort blow-off valve, all from Turbo Smart. A pair of JBA shorty truck headers with short tubing sections feed the turbos.
The Big Bang Boost
In Naturally aspirated form with 1-7/8 headers the LS produced 451 hp and 380 lb-ft of torque and with the wastegate springs set to just 7 psi of boost, the Turbo LS produced more than 600 horsepower. With proper tuning and a swap to 14 psi springs, this baby LS pushed past 900 horsepower. With the manual controller, they were able to get 26.8 psi and wring the Turbo LS 0ut to the tune of 1,203 horsepower!
The baby LS did fail on the dyno, but not in the way you would’ve see coming. The next dyno pull after 1,203 horsepower, aiming to creep the boost up bit by bit to 27 or 28 psi, the Turbo LS suffered an ignition failure. Nothing broke, no big explosive finale, a simple electrical failure.
A Sheep In Wolf’s Clothing
You might have noticed that as we recap this pinnacle moment in recent LS history, we’ve referred to this dyno mule as a “truck LS”, “turbo LS”, or “baby LS” and have never stated its displacement. Well, that’s because they didn’t even know, either! What they thought they picked up was a typical LM7 code 5.3 liter LS, which is found in most 1999-2006 trucks and SUVs.
But after the teardown to inspect the Turbo LS after the 1,200-plus horsepower dyno runs, it turned out to be a 4.8! These two engines look identical on the outside with the same cylinder heads, intake manifold, exhaust, oil pans, even the blocks are the same. They only noticed after they ran the casting number off the crankshaft to find it was the shorter stroke version only used in the 4.8s.
(pictures and info courtesy of Hot Rod magazine)
