November 2010 Chevy High Performance Q&A - Performance Q&A

Kevin McClelland Oct 12, 2010 0 Comment(s)
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A: What an awesome swap. Your Chevelle will be a kick in the pants to drive with the torquey LQ9 Gen III 6.0L and the Tremec manual trans. Achieving your rear-wheel horsepower goal will be very easy with your base engine. We just want to make sure it'll have the street manners you're looking for.

You mentioned the LS6 camshaft as a possibility for a cam upgrade. This would be perfect for the street manners and power accessories load that will be on the engine at idle. The only issue is that you will have a very mild (think stock) idle quality. The '02-04 LS6 camshaft produced 405 hp in those years. The camshaft specs out at 204/218 duration at 0.050-inch tappet lift, 0.550/0.550-inch max lift, and is ground on a 117.5 separation angle. Not only is the camshaft ground with very wide centers, the inlet centerline is installed in the engine at 120, which is very retarded. The wide separation angle gives you great idle quality but has very little overlap. Also, with the centers this wide you have a very broad torque curve. Now, if you're looking for the Saturday night hamburger stand idle quality with outstanding torque and power, check out the Comp Cams 275THR9 Thumpr. This cam specs out at 219/233 degrees duration at 0.050 inch tappet lift, 0.553/0.536-inch max lift, ground on a 109 separation angle, and installed at 103 degrees intake centerline. This camshaft will give you outstanding midrange torque in your LQ9 with an aggressive idle. This will work well with your manual trans car, and work with the EZ EFI you wish to use.

As for the intake, we recommend the Edelbrock Performer RPM. The dual-plane design will give you more midrange torque over the single-plane design. The open-plenum, single-plane will make more peak horsepower, but it sounds like you're looking for a great driver. Pick up a PN 7118 manifold and timing module kit, which includes the manifold and an MSD timing module and harness for the 24X-based Gen III LQ9 engine you're using. This timing module is a standalone unit with six preprogrammed spark curves, a rev limiter, and a two-step.

Finally, the EZ EFI is the neatest thing since sliced bread. The quick-learning fuel-tuning capabilities of this system are impressive. Since you are putting this into an early Chevelle we'd recommend going with the master kit PN 30227-KIT, which comes with everything you need: the ECU, wideband O2 sensor, wiring harness, fuel injectors, fuel pump kit, control relays, and the innovative 4150 throttle body. This will give you the best rounded performance and fuel economy out of your late-model-powered muscle car.

Shoot us come pictures of your Chevelle when you're done-we'd love to see your finished product. Enjoy the power and driveability of your Gen III.

Tuning In The 21st Century
Q: I read your column in the Jan. '10 issue with great interest and have a question. What procedure would you use with a UEGO to tune a street engine without going to a strip?
Bob Fuertinger
Via email

A: As always, we would never recommend or condone breaking any traffic laws or speed limits. Safety must be our first concern. That said, the wideband O2 sensor can be used for tuning on the street with no problems. Let's figure out some creative ways to get to WOT!

Before you perform any power tuning, make sure you tune your part-throttle fuel mixture in the 14.7:1 range. This is where the engine converts fuel the most efficiently for emissions and is very close to best fuel economy. In some engines you can even run the engine slightly leaner than 14.7 and still retain good performance and driveability to pick up a little more mileage.


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