1966 Chevelle | Carburetor to Holley Terminator EFI Conversion

Hagerty puts the classic carburetor-versus-EFI debate to an actual test, converting Parts Finder specialist Davin Reckow’s own 396 big-block Chevelle to a Holley Terminator throttle-body system and measuring the results every way that matters: feel, chassis dyno, eighth-mile drag strip times, and real-world gas mileage. It’s less opinion and more hard data for any big-block owner weighing the same swap. The numbers might surprise carburetor purists.

Swapping a carburetor for fuel injection is one of those upgrades that sparks genuine arguments in classic car circles — purists insist it strips away the mechanical soul of a big-block, while practical owners insist they’re tired of flooding, vapor lock, and fiddling with jets every time the weather changes. Hagerty decided the only honest way to settle the debate was to actually run the numbers, taking a 396 big-block Chevelle belonging to their own Parts Finder specialist and putting a Holley Terminator EFI system through every kind of test they could throw at it. What follows is less opinion and more hard data, measured on a drag strip, a chassis dyno, and even at the gas pump.

Meet the Chevelle — and the Man Behind the Wrench

The car at the center of this test belongs to Davin Reckow, who works as Hagerty’s Parts Finder specialist — meaning his day job already revolves around sourcing correct components for classic muscle cars, giving him a level of hands-on expertise most owners considering this same swap simply don’t have. His Chevelle carries the classic 396 cubic-inch big-block, one of the most common and best-supported engine options Chevrolet offered during the Chevelle’s muscle-car heyday, which makes it a genuinely useful test subject: whatever Davin learns from converting his own carbureted 396 to electronic fuel injection is directly applicable to thousands of other big-block Chevelle owners weighing the exact same decision.

⚑ Featured Gear

Start Car Conversations →

← Prev Next →

As an Amazon Associate I earn from qualifying purchases.

What the Holley Terminator Actually Changes

The Holley Terminator system is a self-tuning throttle-body EFI kit designed specifically to replace a carburetor without requiring the kind of full aftermarket wiring harness and standalone ECU tuning that scares off most classic car owners. It uses onboard sensors to continuously adjust the air-fuel mixture in real time, largely eliminating the flooding, cold-start struggles, and altitude-related tuning headaches that carbureted big-blocks are notorious for. For an engine like the Chevelle’s 396, that self-adjusting behavior promises real-world benefits beyond just a cleaner engine bay: more consistent starts, smoother idle, and fuel delivery that automatically compensates for temperature and elevation changes without the owner ever touching a jet or an idle mixture screw.

The Butt Dyno Verdict

Before bringing out any instruments, the team runs what gearheads affectionately call the ‘butt dyno’ — simply driving the car and gauging the difference by feel. It’s an unscientific but genuinely important test, since plenty of upgrades that look great on paper end up feeling worse from behind the wheel, whether through altered throttle response or a flatter power curve. For a big-block Chevelle that’s spent its life responding to a carburetor’s mechanical linkage, switching to electronically metered fuel delivery changes the throttle feel in ways that can only really be evaluated by someone who already knows exactly how the car used to drive.

Putting Numbers on the Chassis Dyno

From there, the Chevelle heads to a chassis dyno for the kind of hard, repeatable data that settles arguments — measuring exactly how much power and torque the 396 produces before and after the EFI conversion under controlled conditions. Chassis dyno testing strips away variables like road surface, temperature, and driver technique that can muddy real-world comparisons, isolating the engine’s actual output with far more precision than a seat-of-the-pants impression ever could. For an engine swap this significant, having genuine dyno numbers to back up the anecdotal ‘it feels different’ reaction is exactly what separates a credible test from a marketing video, and it’s clearly why Hagerty built an entire testing regimen around this single Chevelle.

The Quarter — Well, Eighth-Mile Truth

No performance claim means much without a run down the strip, so the team also takes the Chevelle to a drag strip for a series of eighth-mile passes, comparing elapsed times and trap speeds before and after the conversion. It’s arguably the most honest test in the entire video, because a drag strip doesn’t care about seat-of-the-pants impressions or dyno-room conditions — it produces a number on a timeslip that either backs up the EFI conversion’s promises or exposes them as marketing hype. For a big-block Chevelle owner deciding whether a Terminator swap is worth the cost and installation time, watching real elapsed times change on an actual drag strip carries more weight than almost any other test in the video.

The Test Most Owners Actually Care About

Beyond raw performance, the team also measures fuel economy before and after the swap, addressing the question that matters most to owners who actually drive their classic cars regularly rather than trailering them to shows. Carbureted big-blocks have a well-earned reputation for thirsty, inconsistent fuel delivery, particularly in stop-and-go traffic where a carburetor’s mechanical limitations show up most clearly. An EFI system’s precise, computer-managed fuel metering theoretically closes that gap significantly, and putting real mileage numbers behind that promise — rather than just assuming it’s true — is exactly the kind of practical, ownership-focused testing that separates Hagerty’s content from a typical parts-company promotional video.

The Bottom Line for Carbureted Big-Block Owners

By running Davin’s own daily-driven Chevelle through every test available — feel, dyno numbers, drag strip times, and fuel economy — Hagerty gives carbureted big-block owners something rare in the endless EFI-versus-carburetor debate: an actual dataset instead of just another opinion. Whether the results settle the argument for purists who value mechanical simplicity over convenience is a different question, but for owners who drive their classic Chevelles regularly and are tired of fighting a temperamental carburetor, this video lays out exactly what a Terminator conversion delivers in hard numbers, not just marketing promises. Comments on the video have already flagged it as one of the more thorough EFI reviews they’ve seen, which says as much about how rare real testing data is in this space as it does about Davin’s own Chevelle.

One Test, Four Ways to Judge It

For big-block owners still on the fence, the four-part testing format itself is arguably as valuable as any single number it produces. A viewer weighing this exact swap doesn’t just get a marketing claim about smoother idle or better mileage — they get a Chevelle owner’s actual butt-dyno impression, a documented chassis dyno chart, real eighth-mile timeslips, and a fuel economy comparison, all performed on one consistent test vehicle rather than stitched together from unrelated cars. That kind of apples-to-apples testing is unusual enough in the classic car space that it’s worth the video’s runtime on its own, independent of which way any individual viewer ultimately leans in the carburetor-versus-EFI debate.

Watch the full video and tell us what you think — comments are open below.

Share your thoughts in the comments below.

Republished by Blog Post Promoter

Related posts:

1970 Chevelle SS396 vs Henry J “Green M&M” – 1/4 mile Nostalgic Drag Race – Road Test TV Single Plane vs Dual Plane Manifolds How To Choose A Carburetor Ford Flathead V8 Engine Rebuild Time Lapse Is the Ford 427 the Ultimate Ford Racing Engine? 69 Camaro 540 vs 66 Chevelle 427 Six Strange Muscle Car Facts – Strange & Extreme Quite possibly the RAREST Mustang in the world! ONLY 2 IN THE WORLD! A Chevy Impala that defines “Muscle car” – /BIG MUSCLE How-To Machine Chevy 350 Small Block Engine Motorz #64