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Laurie Houghton's 1973 MGB with Rover 3.9L V8

Laurie Houghton · 1973 MGB

MG MGB

BritishV8: the site for enthusiasts of modified British sports carsas published in BritishV8 Magazine, Volume XVII Issue 1, July 2009, with 2010 updates

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 1973 MGB converted to Rover 3.9L V8 power for hillclimb and circuit use

Laurie Houghton converted his California-import 1973 MGB to run a Range Rover Discovery 3.9L V8 with EFI, paired to a Toyota 5-speed gearbox and a Ford 8 inch rear end. The write-up details the engine, chassis and brake work needed to fit a V8 low in the bay, plus later brake upgrades and a floor reinforcement fix after uncovering a weakness caused by the car's increased torque.

Specs

As stated in the original write-up.

Engine
Range Rover Discovery 3.9L V8, 8.1:1 compression, aftermarket cam (280 degree duration, 0.450" lift), deeper baffled Range Rover sump with larger bore oil pick-up, modified Rover intake manifold
Fuel & Ignition
Carter lift pump to surge tank in RH battery box, Bosch high pressure EFI pump, Discovery EFI injector and ancillary wiring, Haltech F9 programmable EFI computer, standard electronic SDI distributor
Cooling
Custom aluminium radiator with single electric cooling fan
Exhaust
4-into-1 headers exiting through inner guards, single collector, 2.5 inch pipes into dual mufflers
Gearbox
Toyota W58 5-speed with 0.78:1 fifth gear, Australian-made Dellow bell housing, standard Range Rover clutch and pressure plate, fork type release, Toyota slave cylinder
Driveshaft
Custom built Toyota-to-Ford driveshaft
Rear axle
Ford 8 inch center section with 3.27:1 gears and limited slip differential, married to MGB (Salisbury) tubes, custom axle shafts
Front suspension
650 lb lowered competition springs, 7/8 inch diameter sway bar
Rear suspension
Stock MGB roadster springs, Koni telescopic shocks, anti-tramp rods, Panhard rod
Brakes front
BMW Mini Cooper S vented rotors (294mm OD x 22mm thick) with Nissan GTR (R33) 4-piston aluminum calipers and stainless steel braided lines; originally Peugeot 504 vented rotors with Rover SDI 4-piston calipers
Brakes rear
Mitsubishi rotors with Nissan R31 calipers, MGB hand brake lever
Brake pads
Hawk HP+
Wheels/Tyres (circuit)
Volk Racing 15x6.5 wheels with Silverstone 195/55/15 road legal race tyres
Wheels (street)
15x6.0 Nissan Silvia wheels
Chassis
Firewall modifications for V8 engine and steering column, custom radiator supports and V8 engine mounts, enlarged radiator splash panel area, fabricated reinforcement in boot floor for Panhard rod and rear spring mount
Body
Sebring style front and rear valances
Interior
Roll hoop, 6-point racing harness for driver seat, standard MGB instruments except VDO electronic speedometer
Weight
1980 pounds
Performance
120 KW at the rear wheels, 394 Nm torque on 98 octane unleaded, rev-limited at 5400 rpm

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 5

Cooling 2

Gearbox & Drivetrain 6

Suspension & Steering 6

Brakes 8

Wheels & Tyres 3

Interior 2

Electrical 1

  • VDO electronic speedometerVDO

    Replaces the standard MGB speedometer in an otherwise standard instrument set

Other 1

  • 4-into-1 exhaust headers

    Exit through the inner guards, RV8 style, venting hot air from the engine bay, feeding a single collector and dual mufflers via 2.5 inch pipes

Photos

15 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.

Laurie Houghton's 1973 MGB with Rover 3.9L V8Photo: BritishV8: the site for enthusiasts of modified British sports cars
Range Rover Discovery 3.9L V8 with 8.1:1 compression ratio.Photo: BritishV8: the site for enthusiasts of modified British sports cars
Haltech Engine Management System F9-8 Programable Fuel Injection ComputerPhoto: BritishV8: the site for enthusiasts of modified British sports cars
4-into-1 headers exiting through the inner guards.Photo: BritishV8: the site for enthusiasts of modified British sports cars
7/8 inch diameter sway barPhoto: BritishV8: the site for enthusiasts of modified British sports cars
Firewall modifications.Photo: BritishV8: the site for enthusiasts of modified British sports cars
rubber bumper steering universal joint.Photo: BritishV8: the site for enthusiasts of modified British sports cars
Ford 8 inch center and limited slip differential, married to MGB (Salisbury) tubes.Photo: BritishV8: the site for enthusiasts of modified British sports cars
Anti-tramp bar and telescoping shock.Photo: BritishV8: the site for enthusiasts of modified British sports cars
Panhard rod mount.Photo: BritishV8: the site for enthusiasts of modified British sports cars
Reinforcements in the boot floor for the Panhard rod installation.Photo: BritishV8: the site for enthusiasts of modified British sports cars
BMW Mini Cooper S vented brake rotors (294mm outside diameter by 22mm thick.)Photo: BritishV8: the site for enthusiasts of modified British sports cars
Nissan GTR (R33) 4-piston aluminum calipers.Photo: BritishV8: the site for enthusiasts of modified British sports cars
Stainless steel braided brake lines, and caliper adapter brackets.Photo: 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

Starting condition

The base car was a 1973 MGB imported from California in 1993. Houghton used it as the donor for a self-built conversion to a Rover-derived V8, carried out by the owner himself rather than a professional shop.

Engine and drivetrain

A low-compression Range Rover Discovery 3.9L V8 was fitted with a mild cam upgrade, a modified intake manifold, and a Haltech F9 programmable EFI system fed by a Bosch high pressure pump and Discovery injectors and wiring. Drive goes through a Toyota W58 five-speed gearbox the owner already had from the car's four-cylinder days, a custom Toyota-to-Ford driveshaft, and a Ford 8 inch limited-slip rear end mated to the MGB's Salisbury tubes.

Chassis and steering modifications

Mounting the V8 low in the bay required shortening the collapsible steering column, fabricating a new firewall pocket, and installing a rubber-bumper long-shaft rack to gain clearance at cylinder 8. Houghton notes that, in hindsight, angling the column lower and altering the rack mount angle would have been a better approach.

Suspension and brakes

The car runs lowered front springs with a thicker sway bar, and stock rear springs with Koni shocks, anti-tramp rods and a Panhard rod. Front brakes were upgraded over time, ending with BMW Mini Cooper S rotors and Nissan GTR (R33) calipers on stainless braided lines, replacing an earlier Peugeot/Rover setup.

Structural reinforcement

After running anti-tramp bars for some time, the increased torque of the V8 caused sheetmetal failure in the floor pan and front spring mount. Houghton fabricated and welded in a reinforcement similar to the factory RV8 design, spreading the tramp bar loads into the crossmember.

Progress so far

The conversion was completed in January 2008 and by the time of writing had covered only 200 to 250 miles, as the car is used solely for competition events such as hillclimbs and circuit days at Philip Island. The owner lists further planned brake and engine refinements as future work, not yet completed.

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

  • Angling the steering column lower and altering the rack mount angle would have avoided tight clearance at cylinder 8
  • A Tremec T5 gearbox with a 2.95:1 first gear would suit hillclimbing better than the Toyota W58
  • Anti-tramp bars under high torque exposed weak rear spring mounts and floor pan sheetmetal, requiring fabricated reinforcement

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