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 4029) from Kincardinshire provides a fascinating tale of
how his project was conceived and carried out over a three year
period 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?
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.
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 MGBGT had been off the road
for a couple of
years when I purchased it at the end of May 1999 and it definitely
was not roadworthy, so I towed it back home to Banchory on a trailer.
It had severe corrosion in all the usual places but that didn't matter,
the car was stripped bare in a weekend and the rusty remains discarded.
On the garage floor I was left with a front crossmember, rear axle,
the steering rack and column and a four-cylinder engine with an overdrive
gearbox. I also had the heater, pedal box, dashboard, windscreen wiper
motor, front and rear lights, some scratched glass and a tatty interior.
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.
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.
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 a new plastic reservoir type didn't
as the cap fouled the bulkhead.
To update the front
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 (Photo:
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 the same diameter
as the standard MGB but thicker. The dust shield needed a very slight
modification because the SD1 calliper is larger than the MGB one
but apart from that the callipers just bolt on and the car looks
as if it was originally manufactured with them.
Rear suspension and disc brake conversion. (Photo: Geoff
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.
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.
Engine bay is very neat with the injected V8 power unit.
(Photo: Geoff King)
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 be bolted to the engine
first; they had to be placed in the inner wing holes then the engine
fitted and then the manifolds bolted to the engine. 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
I used an early bolt-on tank, which has a 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
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 seen that on a B before
but it works perfectly and keeps the tube runs as short as possible
and away from the heat. I also routed the rear brake line and main
battery cable up the side of the tunnel beside the gearbox, well
clear of the exhaust from the right bank of cylinders.
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.
I fitted electric
windows and remote central locking with an immobiliser and alarm.
I also have a CD radio cassette player with an electric aerial in
the rear wing; the 6 disc autochanger is in the boot. The dashboard
is late model MGB with 3 separate dials for fuel level, oil pressure
and water temperature. All the gauges are new, everyone seems to
fit magnolia faced gauges but mine are black with chrome bezels.
I wanted the indicator switch on the left of the column so I fitted
a late MGB switch upside down on the left for main and dip beam,
indicators and horn. The switch on the right for wipers and washers
is from a
down is flick wipe
and up is the two speeds, press in for the washers. There is also
a variable wiper delay and wash wipe module. Both switch stalks are
from a Mini so the graphics are the correct way up and the car looks
as if it left the factory like it.
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
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".
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)
car looks almost standard, although the RV8 bonnet does have a bulge
and the single exhaust pipe is a little larger than an 1800, there
are also a couple of V8 badges and the wheels are a little larger,
however, under the skin it is thoroughly modern and well able to
keep up with everyday traffic. It is fast and safe and I'm still
driving everywhere with a big grin on my face.
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!