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David Duquette's 1974 MGB-GT V8 conversion

David Duquette · 1974 MGB-GT

MG MGB GT

BritishV8: the site for enthusiasts of modified British sports cars

Read the full write-up at BritishV8: the site for enthusiasts of modified British sports cars ↗

Photo: BritishV8: the site for enthusiasts of modified British sports cars

A 1974 MGB-GT converted to Rover 4.2L V8 power

David Duquette had his MGB-GT converted by Rob Medynski at MGTs in New Jersey to run a built Rover 4.2L V8 with ported heads and a TR8 five-speed gearbox. The write-up is a concise spec sheet covering the engine build, cooling upgrades, driveline swap, and suspension and wheel choices made to support the V8.

Specs

As stated in the original write-up.

Engine
Rover 4.2L V8 with ported and polished heads, Vitesse valves, 9.5:1 compression, Edelbrock Performer manifold milled for hood clearance, Carter 9410 carb, biggish cam, MSD 6AL ignition with Mallory Unilite distributor; about 17mpg
Cooling
Customized radiator with 2 inch extra-long 4-row core
Exhaust
Jet-Hot coated block-hugger headers into single 2.25 inch stainless steel exhaust
Transmission
Triumph TR8 5-speed
Rear Axle
MGC rear axle (wire wheel type, 3.07:1 gears) with Quaife limited slip differential
Suspension
Stock MGB front; rear has BA composite leaf springs, SPAX telescoping shocks, Hopkinson sway bar kit; traction bars planned
Brakes
Stock MGB
Wheels/Tires
Panasport 15 inch wheels with 195/60R15 tires
Body
Stock MG Teal Blue
Interior
140 mph MGC speedometer

Parts used

Parts named as used in the original write-up, grouped the way the Parts page groups them. Where one of the shops we index lists the same thing for this car, it is shown underneath with a link to the shop.

Engine 4

Fuel & Ignition 4

  • Edelbrock Performer intake manifoldEdelbrock

    Milled at a slight angle for extra hood clearance

    In the shops
    V-6 Intake Manifold ↗Moss Motors – Triumph TR6/TR250· $14.72 USD
    Intake Manifold, Mk VII ↗Moss Motors – Triumph TR6/TR250· $0.00 USD
    Intake Manifold, Mk VIII/Mk IX ↗Moss Motors – Triumph TR6/TR250· $0.00 USD
  • Carter 9410 carburetorCarter

    Carburetor fitted to the V8

  • MSD 6AL ignition boxMSD

    Ignition control unit for the V8

  • Mallory Unilite distributorMallory

    Distributor paired with the MSD ignition box

Cooling 2

Gearbox & Drivetrain 3

Suspension & Steering 3

Wheels & Tyres 1

Interior 1

  • MGC 140mph speedometerMGC

    Speedometer fitted to suit the car's higher performance

Other 2

Photos

9 pictures collected from the write-up, in the order they were posted, shown from BritishV8: the site for enthusiasts of modified British sports cars. A picture opens larger here, with the way through to the page it is on.

David Duquette's 1974 MGB-GT with Rover 4.2L V8Photo: BritishV8: the site for enthusiasts of modified British sports cars
David Duquette's MGBPhoto: BritishV8: the site for enthusiasts of modified British sports cars
engine steady barPhoto: BritishV8: the site for enthusiasts of modified British sports cars
rear-mounted 8 inch fansPhoto: BritishV8: the site for enthusiasts of modified British sports cars
four cooling fansPhoto: BritishV8: the site for enthusiasts of modified British sports cars
MGC 140mph SpeedometerPhoto: BritishV8: the site for enthusiasts of modified British sports cars
Panasport 6J wheelsPhoto: BritishV8: the site for enthusiasts of modified British sports cars
David Duquette's garagePhoto: BritishV8: the site for enthusiasts of modified British sports cars
Donate Now!Photo: BritishV8: the site for enthusiasts of modified British sports cars

How it was done

The conversion

The MGB-GT was converted to V8 power by Rob Medynski at MGTs in New Jersey, fitting a Rover 4.2L engine in place of the original four-cylinder.

Building the engine

Woody Cooper at The Wedge Shop ported and polished the heads and specified a biggish cam. The engine runs Vitesse valves, 9.5:1 compression, an angle-milled Edelbrock Performer manifold for hood clearance, a Carter 9410 carburetor, and MSD/Mallory ignition. Fuel economy is around 17mpg.

Cooling and exhaust

To cope with the V8's heat, the radiator was customized with an extra-long 4-row core, and four cooling fans were fitted. Jet-Hot coated block-hugger headers feed into a single 2.25 inch stainless exhaust.

Driveline

Power goes through a Triumph TR8 5-speed gearbox to an MGC rear axle running 3.07:1 gears and a Quaife limited slip differential.

Chassis and wheels

The front suspension remains stock MGB, while the rear uses BA composite leaf springs, SPAX telescoping shocks and a Hopkinson sway bar kit, with traction bars planned. Brakes stay stock MGB. The car rolls on 15 inch Panasport wheels with 195/60R15 tires, finished in the original Teal Blue paint.

A summary in our own words. The full account, with all its detail, is in the original write-up: read it at BritishV8: the site for enthusiasts of modified British sports cars ↗

Worth knowing

  • Milling the intake manifold at an angle can gain crucial hood clearance for a V8 swap
  • Extra-long, multi-row radiator cores plus multiple fans help manage V8 cooling demands in a small engine bay
  • Using an MGC rear axle gives a ready source of stronger gearing and a wire-wheel compatible housing
  • Pairing an MSD ignition box with a Mallory Unilite distributor supports reliable high-performance ignition

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