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Turbo Inline Six Engine - What's Your Problem?

Dread Revival
Gary Tetu, Scottsdale, AZ: I really enjoy reading Car Craft, but an article titled "Disco Dread" in your June '09 issue prompted me into action. The article broke with your unwritten rule to avoid the Corvette with: "The best deal in performance cars on the planet-the C4 Corvette." Your article basically promoted finding an early-year C4 for less than $5,000 and then replacing the original engine with an LS engine. I loved it.

I went looking for a low-buck C4. What I found were lots of serious problems attached to each car. Each $3,000, $4,000, or even $5,000 C4 needed bodywork, paint, a new interior, and mechanical repairs. When I added up all these items, it didn't leave any money for a performance engine.

Then I came across a torch red '96 Corvette with the LT4 engine, ZF six-speed trans, and just 41,000 miles on the clock. The car had been very well cared for, so all the mechanicals were in tip-top shape. I feel the LT4 has close to the same performance as a stock LS1 engine.

I paid $13,700 for the car and did not have the fun of all the busted knuckles rebuilding the car. But I think I came out ahead by going for the newer car with the LT4 engine and six-speed. You guys were right-the C4 is the best deal in performance cars on the planet.

Jeff Smith: Sounds like you found a winner, Gary. If I can be so bold, how about a suggestion to tune up the LT1/LT4 motor? I recently ran across a company called EFI Connection that offers a great upgrade for this engine's Achilles heel-the OptiSpark ignition. As you probably know, the LT1/LT4 drives the distributor off the front of the cam with the plug wires coming off the front of the motor. While the concept was good-improved ignition timing accuracy using optical pickups-moisture captured inside the housing caused all kinds of grief, especially for the '92 to '94 versions. Plus, when you have to replace the module (around $90) or the cap and rotor ($280), it quickly gets expensive.

The EFI Connection alternative is to pull most of the distributor off of the engine and convert to a 24X crank sensor wheel and a cam sensor, all located behind a new aluminum timing cover. EFI Connection builds a custom engine harness to adapt a late-model GM LS1-style ECM that will drive the LS1-style distributorless ignition system with the coils located either on the valve covers or relocated somewhere in the engine compartment. For the LT1/LT4, EFI Con-nection even has a do-it-yourself kit that includes the instructions and all the harness components necessary. To do this, you'll need a GM LS1 computer ($150), the coils, and to figure out a way to mount the coils. Or, EFI Connection can build a complete harness ready to go for $650 (which is a great price) to which you just add the coils and the computer. You will also need to tune the system with a software upgrade through EFILive or HP Tuners. All this could easily run more than $1,100, so it's not cheap. But we're hearing all kinds of good things about this conversion. Another advantage (this doesn't apply to those with six-speed manuals) is the LS computer will also control a 4L60/65E electronic overdrive automatic, which means you don't have to invest in a separate controller that can cost between $800 and $1,000. In that sense, it's like getting an electronic trans controller for free. EFI Con-nection now has a 58X conversion that will use the later computers that can also drive the late-model electronic automatic trans.

I also found a variation of this idea from Delteq that converts the LT1/LT4 engines to a waste spark distributorless ignition using the Cadillac Northstar system. Waste spark systems use four coils with twin output terminals that fire two cylinders simultaneously. This reduces the number of coils needed but fires each coil twice for the entire 720-degree, four-stroke cycle. The Delteq conversion system sells for $694.73. It is less expensive because Delteq uses the OptiSpark sensors to trigger the coils. This would appear to work well because the sensors were rarely the problem in the original OptiSpark.

More Info

EFI Connection
Erie, PA

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