V8 Roadster Conversion project - from dream to reality!

V8 Roadster Conversions are very popular with V8 enthusiasts and come in a variety of specifications. Here Geoff King (Tartan Red 4309) from Kincardinshire provides a fascinating tale of how his project was conceived and carried out to produce an award winning V8 Roadster with a wonderful specification and performance. Geoff converted his rusty 1972 MGBGT 1800 to a V8 Roadster over a three year period and completed the project in August 2002. It has a 3.5 litre injected engine with a five speed gearbox, independent rear suspension, unequal length double wishbones, and coilover dampers front and rear. The brakes have been upgraded with disc brakes front and rear, with four pot calipers on the front. It looks standard but it isn't! (May 04)

How did the project come about?
While in the local library one day, I noticed Roger Williams' book 'How to give your MGB V8 power'. The sound of a V8 in a Rover SD1 that I had some years ago and its smooth effortless power came back into my mind and I thought how I had missed my MGB during the time our family were growing up, but now the seed was sown and I knew what I was going to do. I would build a Tartan Red V8 Roadster with alloy wheels, like the one that I had in my carefree youth but with enough power to keep up with the traffic of today. I knew that new MGB shells were being manufactured and my plan was to buy a cheap roadster as a donor and build a car using a new body. The car would look original but it would be modern under the skin with electronic ignition and fuel injection, up to date suspension and brakes and the "toys" that we expect in many cars today.

First a complete Rover SD1 was purchased for its V8 engine and 5 speed LT77 manual gearbox. I overhauled the 3.5 engine and fitted new rings, bearings, rocker shafts, 3.9 cam and duplex roller timing chain. To help the engine breathe I smoothed and matched the ports in the heads and fitted the latest 'Vitesse' type valves. The gearbox was rebuilt with new baulk rings and bearings.

A suitable donor roadster proved to be elusive in Scotland (by suitable I mean cheap and tax exempt) and I eventually bought a 1972 GT in Dumfries. The 1800 MGB GT had been off the road for a couple of years when I purchased it at

The engine and gearbox were sold and the chrome bumper front crossmember swapped for a rubber bumper one. I purchased a twin circuit brake and clutch master cylinder pedal box assembly, a rubber bumper steering rack and a collapsible column, the original items were sold. The '72 dashboard was also sold and a late model MGB version bought to suit the collapsible column. The seat runners were retained but the remainder of the interior was thrown away. The glass was no use either - there was not much left of the original GT.

Bullet door mirrors are meant for a Mini but fit perfectly on the original MGB mirror plinth. (Photo: Geoff King)

Difficulties with the new V8 Roadster shell
I placed my order for a special V8 roadster shell with the fittings and brackets etc (or so I thought) for the V8 engine, 5 speed gearbox and ancillaries. The shell would have apertures in the inner wings for a RV8 style exhaust manifolds and I also specified a RV8 bonnet to give clearance for the fuel injection plenum chamber. The shell was delivered in November 2000 finished in two pack Tartan Red and as it was lifted off the trailer and pushed into my garage on that cold, dark evening it looked wonderful with gleaming paintwork. Unfortunately, the next day a more careful inspection revealed that the doors, boot and bonnet which were supposed to be 'fitted' were, in fact, simply 'attached' and many hours were spent getting the panel gaps as even as possible. I was to find more and more defects with the shell and I can only assume that I had an early version that still needed some

development work. To be fair the supplier (or rather the shell manufacturer) paid for the errors to be corrected but in my opinion they should not have been there in the first place. There were too many defects with the shell to ignore but following some correspondence with the supplier I was advised that I "should leave a V8 conversion to the professionals"; however, having seen some of the workmanship from so called craftsmen, I knew I could do at least as well if not better. I would also have the satisfaction of doing it myself and for better or worse I would do it my way.

Building the V8 Roadster
The build commenced; the uprated heater and fan being the first items installed then the twin circuit brake master cylinder and pedal box. The clutch master cylinder is a MGBGTV8 type with a metal reservoir because a new plastic reservoir type didn't fit as the cap fouled the bulkhead. To update the front suspension and brakes I modified the rubber bumper type crossmember with a John Hoyle coilover damper conversion with unequal length double wishbones replacing the standard lever arm dampers.

Front suspension with the coilover damper conversion and the lagged RV8 exhaust above and behind the brake disc. (Photo: Geoff King)

The suspension has SuperFlex® bushes and is fully adjustable for ride height, damper rate, and caster and camber angles. To complete the front suspension I fitted a 7/8 inch anti roll bar and modified the steering with a 'quick rack' assembly to reduce the number of turns lock to lock. For the brakes, Rover SD1 non-vented, single line, 4 pot callipers were a relatively cheap and easy brake upgrade. The big callipers were bolted on with thin wall sleeves (the holes are metric, the bolts imperial) and connected with metric to imperial stainless steel braided hoses. Solid ½ inch thick, 10.75 inch diameter MGBGTV8 discs were used, they are

I fitted the refurbished rear axle, rebuilt with a 3.07:1 ratio crown wheel and pinion, but after less than 500 miles the antiquated live axle and cart springs were sold and replaced with John Hoyle's Independent Rear Suspension. Like the front suspension, the IRS kit from John is a high quality product, well designed and manufactured. The ride height, damper rate and camber are all fully adjustable and the bushes are again SuperFlex®. Incidentally, all the bushes used in the front and rear suspension are standard MGB size (front lower wishbone) so future replacements should not be a problem. The total weight of the suspension is slightly more than the live axle but the unsprung weight is much less. The tube axle assembly, springs and dampers weighs close to 100 Kgs, 85 Kgs unsprung. The IRS is approximately 105 Kgs with less than 46 Kgs unsprung.

Rear suspension and disc brake conversion. (Photo: Geoff King)

I purchased a refurbished Sierra differential with 3.14:1 CW&P (the highest standard ratio available), exchange-shortened drive shafts and new drive flanges, dust shields, discs, pads, wheel bearings & seals and calliper overhaul kits. A scrap Ford Scorpio donated its hubs, drive shafts and brake callipers; these were refurbished prior to being reused. Assembly of the rear suspension was straightforward with Sierra discs and rebuilt callipers; the completed sub-frame was then offered up and bolted to the chassis. No new holes are necessary; the existing front spring eye, the lever arm damper and check strap mounts are used - 8 bolts in total. A new, heavy duty propshaft to mate the Rover LT77 gearbox to the Sierra diff was purchased from GKN Driveline - suppliers of the original MGB propshafts.

The engine and gearbox went in easily but the RV8 style exhaust manifolds couldn't be bolted on after the engine was in position, so engine had to come out again. The manifolds couldn't

Engine bay is very neat with the injected V8 power unit. (Photo: Geoff King)

Electronic fuel injection was obtained from a Range Rover, the ECU being from a 3.5 while the plenum, hot wire airflow meter, manifold and injectors were from a 3.9. It all fits under the RV8 bonnet, as you would expect, but only just. Considering the wiring is from a Range Rover it all fits very neatly in the MGB with the ECU mounted inside the cabin on the top of the passenger footwell. For the fuel supply I used an early bolt-on tank, which has the fuel pipe in the tank side, with a late fuel level sender which also has a fuel pipe, so as to have a flow and return to the tank. A section approximately eight inches square was cut out of the top of the new tank and a swirl pot from a Ford Granada welded inside. I mounted a Bosch, high-pressure fuel pump together with a fuel filter on the side of the battery box, the pump being level with the bottom of the fuel tank because high-pressure pumps have poor suction. Stainless steel pipes were used for the fuel supply and return and as the wiring harness was routed inside the car the return fuel pipe uses the old supports and brackets for the wiring.

One of the problems with the new shell was that the radiator support diaphragms were in the wrong place with the left side being some ¾ inch further forward compared to the right making it impossible to fit the radiator. The remote oil filter bracket was also incorrectly positioned so the supports were cut off and new ones welded in place and painted again. I originally fitted a standard MGBGTV8 radiator together with twin electric pusher fans but recently replaced this with a high efficiency radiator from Clive Wheatley.

For the brake lines I used, or rather tried to use, an Automec copper pipe kit but of course as my car is made from parts of various years and models very little fitted. I ended up removing the gland nuts from the copper tube and cutting Kunifer tube to the correct length. To avoid the exhaust I routed the front brake pipes through the inner wings above the dampers - I haven't

Interior and trim
The car was now more or less mechanically complete so on to the interior. I purchased a complete set of biscuit coloured panels and carpets including the boot and fitted heating elements to the leather seats which also have headrests. The combined door pulls and armrests are colour matched and are similar to RV8 ones but are actually from a scrapped Vauxhall. The Vinylkote custom colour aerosol was more expensive than the armrests themselves but the colour match is perfect.

Door panels with the armrest from a Vauxhall sprayed with "Vinylkote" to match the biscuit interior. Note no speakers or window winders in the doors leave them looking very neat. (Photo: Geoff King)

Cockpit looks just right! (Photo: Geoff King)

I fitted electric windows with the switches fitted to a small panel where the ash tray is normally located. There is also remote central locking with an immobiliser and alarm, and heated seats with switches in the central console between the heater controls and the clock. I also have a CD radio cassette player with an electric aerial in the rear wing and the speakers in the kick panel in front of the doors with another two in the rear side panels just in front of the wheel arch. The speaker covers are sprayed a biscuit

First firing and MOT test
I was pleasantly surprised when the engine fired up at the first attempt but some underseal melted and dripped onto the exhaust filling the garage with smoke during the first 20 minutes or so running in the cam at about 2,000 revs. My wife thought the garage was on fire!

On the 2nd of August 2002 the car passed the MOT (first time of course) it had already been inspected by the traffic police who checked the body and engine numbers, I had also been interviewed by the police and issued with a new VIN by the DVLA. My local MOT station checked that the new VIN was hard stamped into the shell and the car was registered as an "MGBGT Convertible".

Result is a wonderful V8 Roadster
The engine runs at around 90oC with occasional excursions to 95 or so and the modern suspension is excellent, driving the car around the Highland roads is a real joy; no more front wheel patter on rough surfaces, there is very little roll and the back end stays firmly planted to the road. Axle tramp has been eliminated and on hard acceleration the car just squats a little. The brake balance seems perfect with the four pot Rover SD1 callipers at the front and single pot Sierra callipers at the rear.

Externally the V8 Roadster looks standard with only the RV8 bonnet bulge and V8 badges - but it is a thoroughly modern car and a delight to drive. (Photo: Geoff King)

From start to finish the conversion of an old 1800 GT to a fuel injected V8 Roadster took some three years. New components were purchased for repairs and safety critical items but I used scrap yards and second-hand parts wherever possible and many items were purchased from the MG spares day at Stoneleigh 450 miles from home. I bought a new shell because I converted a GT to a roadster and the GT donor was a basket case destined for the scrap yard I also wanted as strong a shell as possible for the V8 power not one riddled with rust. Despite recommendations that the project should be left to the professionals only the paintwork was carried out by specialists. Everything else, and I mean everything, I repaired, rebuilt, modified and uprated myself.

Would I do it again? Without any hesitation or doubt yes, but my wife wouldn't like it!