Jon's 1971 MGB Racecar Hits the Dyno for First Time: Baseline Power Numbers Revealed

In this episode of Spare Parts, Jon’s classic British sports car—his 1971 MGB racecar—visited Eclectic Motorworks for its first-ever dyno day. It was the first time the MGB had ever been placed on a dynamometer. The objective was straightforward: obtain baseline horsepower and torque measurements to guide future upgrades and tuning.

The results were more impressive than anticipated, particularly during the second official dyno pull. Special thanks to Carl and Owen from Eclectic Motorworks for hosting Jon.

The TTAC Creators Series amplifies voices from across the automotive world, covering culture, dealerships, collections, modified builds, and more. Below is a transcript, summarized by AI and edited by a human staffer.

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The Dyno Day: 1971 MGB

I began the dyno pulls, but I misunderstood the instructions. It couldn’t have gone worse for me. If it actually starts at 122 horsepower, I’ll be impressed. No way.

The Build

For context, this is my 1971 MGB, which I refer to as my racecar. The engine is actually from a 1976 model, featuring small valve heads and HIF4 carburetors from a 1974 vehicle. The motor build includes:

• Flat-top pistons
• A mild street cam
• Dual valve springs
• Electronic ignition
• A balanced bottom end

The engine originally ran with a Weber carburetor. I acquired the entire engine from a wrecked car that had been beautifully restored but unfortunately rear-ended. A close friend had built this motor, and it performed exceptionally well in that vehicle. When the car was wrecked, I purchased the engine, and the entire driveline was installed in my MGB.

Heading to the Dyno

It was a rainy April day when I loaded my 1971 MGB onto the trailer and headed to Holland. The plan was to secure it to the dyno and determine its power output. I didn’t expect to perform extensive tuning; I simply wanted the baseline numbers—though I was prepared to be disappointed.

I had the opportunity to take the MGB to Eclectic Motors in Holland. Carlo generously allowed me to conduct dyno pulls to establish a solid baseline for future modifications and to see what the car could do, given it was essentially built from spare parts.

The Pulls and Technical Troubles

I revved the engine up to 5,000 RPM. A spark flew from somewhere near the front of the motor, and the signal dropped off. Of course, the day didn’t proceed smoothly; that would have been too easy.

I proceeded with the dyno pulls, but