1992 GMC Typhoon LS1 Engine Upgrade - Conversion Immersion

Trading The Typhoon's 4.3L V-6 For A Turbo LS1 And 10-Second Timeslips

John Ryan Feb 1, 2010 0 Comment(s)

If you've been into performance for a long time, it's very possible that the following applies to you as well. Like many performance addicts, Dan Marks of Wonder Lake, Illinois, caught the bug in his teens and he's never been able to shake it. He's owned some quick cars over the years including a 1995 Cobra he turned into a tire-melting 1,100-rear-wheel-horsepower animal. While most folks resign themselves to having fast cars that sleep most of the week and commute in a boring daily driver, the longtime Senior Technician at Speed Inc. simply couldn't have that.

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At the Shcaumburg, Illinois shop Dan was no stranger to making gobs of power with LS technology and turbos. Additionally, he is a longtime fan of GMC Typhoons, and has lusted after them from the first day he laid eyes on one back in the early '90s. However, the high collectability of these vehicles has kept their prices strong and as a result, this was an unfulfilled dream until last year. Dan was browsing on www.SyTy.net, and noticed an ad for an 89,000-mile, mostly stock 1992 Typhoon. Dan haggled over the price and a deal was struck. Modified with only a cold-air intake and chip, the truck was a fun high 13-second ride. Dan did actually put a few hundred miles on the truck before tearing it down, but his goal to combine his longtime admiration of these trucks with a modern LS driveline finally won out and so the truck went under the knife.

Having had years of experience designing and fabricating custom LS-based builds, Dan made a list of goals that included extreme performance, retaining all-wheel-drive, and last but not least, keeping air conditioning for his lengthy commute. Dan started his build by yanking out the factory engine, turbo system, and exhaust. He wisely left the stock transmission and transfer case in place for his initial engine mockup. A junk engine block was used to see what modifications would be needed to shoehorn an LS-based mill in place of the original V-6. While whipping up custom motor mounts was anticipated, Dan also discovered that the factory heater box needed to be clearanced or the engine would not fit. With regards to the LS swap, this was one of the few major modifications needed, other than building a custom transmission crossmember.

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Next, Dan turned his attention to the rest of the driveline. With plans to make somewhere in the neighborhood of 700-rear-wheel horsepower, Marks knew that the factory 700-R4 transmission and wimpy 7.5-inch 10-bolt rearend would last about 10 seconds into his first testdrive. After some research, Finish Line Transmission of Bensenville, Illinois, got the nod to build him a Level V 4L80E transmission, which is rated to handle over 1,000 horsepower. Dan went with another trusted company, Yank, to supply him with a 3,200-stall converter that would have lock-up and handle 800 lb-ft of abusive torque. Custom length chrome-moly driveshafts were ordered from Suburban Driveline, and a '67 Chevelle 12-bolt was narrowed and modified to bolt up to his factory suspension.

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Having sorted out the drivetrain, Dan turned his attention topside to the engine and turbo setup. A used 6.0L iron block stroker, sporting 402 cubic inches, was acquired and then freshened by Advanced Automotive in Roselle, Illinois. They also installed a custom camshaft, which was specified by longtime friend and coworker Jim Moran. A pair of ET Performance 245cc cylinders heads made their way atop the engine along with a GM Performance Parts carb-style intake manifold. A set of Speed Inc. fuel rails, an MSD 90mm throttle body, and a set of 80 lb/hr injectors top off the long-block. Faced with either buying a custom oil pan or making his own, Marks purchased a wallet-friendly 2007 Escalade oil pan, which he cut and modified to fit. Eschewing a rowdy external fuel pump setup, twin Walbro 255 in-tank fuel pumps were installed in the factory gas tank.

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