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LS Power!! Twin 76mm Turbo 4.8L 1200HP & still going!!
The goal of the test was to test the true limits of the LM7, which is the 5.3L truck engine based on the LSx series engines. Pretty much an LS1 with an iron block in a nutshell.
They picked up what they thought was an 5.3L LM7 but, as they found out after the testing was over, it was actually a 4.8L LR4 which is the smallest of the LSx based iron truck engines. One phenomenal part about the engine was the #8 cylinder had a large rust spot etched in it that their hone wouldn't remove....they left it there.
For the top end they upgraded to 2" intake valves, stock exhaust valves and did a very mild port job on the heads. Flow numbers went from 220/220 to 300/220 cfm on the intake and exhaust respectively. ARP studs with Fel-Pro MLS gaskets kept the heads down. A mild Comp Cams cam was installed along with the supplied lifters, pushrods, springs and rockers remained stock. A FAST LSXR intake was installed as well with a big TB.
The short block(except the cam) was all stock. Even the original bearings and rings that were on the motor when it was purchased were reused. They even sanded the rust off the #8 rings and reused them!
Fueling was handled by 75 lbs/hr injectors and upgraded fuel rails. It was run on Rockett 118.
The two turbochargers were CXracing 76mm units run off of flipped shorty truck headers(no name brand headers).
The engine was run for SIXTY dyno pulls over half of which were claimed to be at 1000+ hp. In it's final trim, in between 26 and 27psi, the engine produced just over 1200hp. What stopped the testing was not engine failure but an ignition failure(all sensors and electrical components like the ignition were stock). The engine was 100% a-ok by the end of the testing.
04 GMC RST: TMS Iron 347/S480/4l80E - email@example.com All Boost 05 GMC 2500HD: LLY@372HP/669TQ, 4x4, 8" FabTech, 37" Toyo M/T's, 97 22" Baja Hammer: Boss w/stock 454