Camaro Z28 Carb Dyno Tune: Making a Legend Scream!

A 1969 Camaro Z28 arrived at International Dyno Authority running well under its potential, and step-by-step carburetor tuning — fixing a broken choke plate, adjusting the float and accelerator pump, and re-jetting — found 45 extra horsepower without a single mechanical change. That’s a 20 percent gain from tuning alone on a numbers-matching engine. See exactly how much power was hiding in plain sight.

A carburetor that idles rough and stumbles off the line doesn’t need a bigger cam or another hundred cubic inches — half the time it just needs someone who actually knows what they’re adjusting and why. This 1969 Camaro Z28 came into the shop running noticeably below what its numbers-matching engine should have been capable of, and rather than throwing parts at the problem, the crew put it on the dyno and started working through the carburetor step by step. What they found along the way — a broken choke plate, float settings out of spec, jetting that didn’t match what the engine actually wanted — adds up to the kind of diagnostic story most muscle car owners never get to see happen in real time. How much power was actually hiding in a stock Z28 that just needed to be tuned correctly?

Baseline: A Legend Running Under Potential

Before any adjustments, the Z28 put down a baseline of 231.47 horsepower and 240.62 lb-ft of torque on the dyno — numbers that told the story of an engine mechanically capable of more but held back by a carburetor that wasn’t dialed in correctly. Rough idle and inconsistent air-fuel ratio readings pointed the diagnosis away from anything structural and squarely at the fuel delivery system, which is exactly the kind of problem a careful, methodical tuning session is built to solve.

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Finding the Broken Choke Plate

Initial troubleshooting turned up a damaged choke plate, a small component easy to overlook but capable of throwing off the entire air-fuel mixture during warmup and idle. Repairing it before moving on to any other adjustment was the right call — chasing jetting changes or float settings on top of a broken choke plate would have made every subsequent adjustment harder to read accurately on the dyno.

Float Settings, Accelerator Pump, and the Low-Speed Circuit

With the choke sorted, the team worked through the carburetor’s low-speed circuit, inspected and adjusted the float level, and dialed in the accelerator pump — the component responsible for that immediate shot of fuel when the throttle opens quickly. Each adjustment got its own dyno pass to isolate the effect, rather than changing multiple variables at once and guessing which one actually mattered.

Jet Size: The Final Piece

The last major change involved pulling the carburetor bowl and adjusting jet size, fine-tuning exactly how much fuel the engine received at higher RPM once the earlier fixes had already cleaned up idle and low-speed behavior. That sequencing matters — jetting changes made before fixing the choke plate or float settings would have been chasing a moving target the whole time.

The Payoff: +45 Horsepower, +20 Percent

By the final dyno pass, the Z28 was making 277.01 horsepower and 269.55 lb-ft of torque — a 45.54-horsepower gain, roughly 20 percent, and a 28.93 lb-ft torque improvement, all without a single mechanical change beyond carburetor tuning. For a numbers-matching muscle car where owners are often reluctant to modify anything under the hood, that kind of gain from tuning alone is about as good an outcome as exists.

Documenting the Whole Process

International Dyno Authority documented the entire process rather than just the before-and-after numbers, walking through intro observations, troubleshooting the rough idle, and even a customer review at the end — a level of transparency that turns what could have been a simple stat card into an actual tutorial for anyone with a similarly underperforming carbureted engine sitting in their own garage.

Built to Be a Reference, Not Just a Video

The timestamped breakdown — from initial observations through final results and discussion — also makes the video unusually easy to reference later, letting a viewer jump straight to the accelerator pump adjustment or the final jetting change instead of sitting through the entire session to find the one step relevant to their own carburetor.

Watch the full video and share your thoughts below.

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