Big-Block 1969 Chevrolet Corvette Dyno Test - Corvette Big-Block Party, Part 4

Part 4: Wrap-up, dyno testing, and driving impressions

Paul Sisia Oct 10, 2011 0 Comment(s)
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From the start, this buildup was designed to recreate those glory years of the mid ’60s to early ’70s, when big-block Corvettes reigned supreme. Merely checking off the L71 or L89 engine on the option list back in 1969 (the year our C3 was built) would have given our screaming yellow roadster the much coveted “King of the Road” status. (Yes, the L88 option had more horsepower, but it seemed the only place you could find one was in a magazine or at a racetrack.)

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Those Vettes were aerodynamic and nimble, too. And with four-wheel disc brakes and a state-of-the-art independent rear suspension, they could trounce anything on the street in acceleration, handling, or stopping. The idea for this project was to not just preserve our ’69’s built-in performance attributes, but to elevate them to another level entirely.

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This final feature in the series is where the rubber meets the road, and we have to admit to a certain sense of trepidation. Did we set the bar a little too high? Here’s a quick recap of our wish list:

  • An easy-to-live-with big-block that could run on pump gas and make way more power than an original 427/435
  • A high-tech, fuel-injected, Tri-power setup that would look just like the original L89 and still fit under a stock 427 hood
  • A modern, electronically controlled, four-speed overdrive transmission capable of handling big horsepower and torque
  • And finally, an IRS that wouldn’t explode when we dropped the hammer
  • Throw in some steering, suspension, and braking upgrades for good measure, along with a goal of achieving better gas mileage than the small-block we took out. Maybe we should have titled the project “Mission Impossible”!

    Dyno Testing

    As everyone knows, the dynamometer doesn’t lie. So the acid test for this build would come on the engine dyno at Lamar Walden’s shop, with Rob Walden at the throttle.

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    Rob began by firing up our 454ci engine, which, much to our surprise, idled perfectly at around 800 rpm. If that doesn’t convince you of the superiority of electronic fuel injection, we don’t know what will. It sounded awesome to boot.

    Once the engine was up to temperature, Rob made an initial pull to 5,000 rpm, well below the big-block’s redline. The dyno read 520 hp and 570 lb-ft of torque—not a bad start.

    He then let everything cool down before making a second pull. This one went to 6,000 rpm, yielding dyno readings of 600 hp and 520 lb-ft.

    “If you want more, we can easily spin it 6,500 rpm,” he offered. “It’ll probably do 620-630 hp.” It was getting late, though, and with our 600-horse target already achieved, we decided to call it a night. Besides, if Rob says it’ll do 620, who are we to doubt him?

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    He also pointed to the second dyno chart, which showed 540 hp at 5,000 rpm, as compared with 520 hp at 5,000 rpm on the first pull. “It’ll make more power…as the engine breaks in and the FAST computer self-tunes,’’ he explained.

    For a full breakdown of our big-block’s output at various rpm points, check out the accompanying dyno chart. It’ll make it crystal clear why Rob called this motor a “two-stump puller.”

    Final Touches

    Just prior to our on-road evaluation, it became obvious that a minor adjustment was necessary. The rear of the car was sitting too high, and there was no way to get the ride height correct with the existing hardware. A call to the guys at Van Steel revealed that we needed a “low-arch” 330-pound unit to drop the rear to an acceptable level, control the car’s “squat” under acceleration, and keep the Denny’s “nitrous-ready” halfshafts in proper geometrical alignment. The 330-pound piece would also provide better ride quality for our street application.

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    With the correct rear spring installed, the ride height adjusted, and a four-wheel alignment done, it was time for the car’s maiden voyage.

    On the Road

    Once our ’69 was moving under its own power, it was immediately clear that we had met (or exceeded) all of our goals with the EFI 454/4L60E drivetrain combination. This modern setup really embarrasses the car’s old 406 small-block and 700R4 trans in every area. Add in the steering, braking, and suspension upgrades, and the term “home run” comes to mind.

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    It’s also important to point out that this was not a “custom” build. All of the we used parts are readily available from the suppliers listed in our Source Box, and there was no need for welding or custom fabrication along the way. Factor in that we doubled our horsepower and increased fuel mileage by 50 percent, and the results start to look more like a grand slam than just a home run.

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    So now when someone asks us (and they will ask us), “Does it have a big-block?” we’ll respond, honestly, “Hell, yes!”

    Be sure to visit www.vetteweb.com to see a video of our EFI big-block on the dyno.

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