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Improved cooling with the MGBV8
Gordon Hesketh-Jones
(Harvest Gold 1904) from Cornwall has done over 200,000 miles in his V8 and has
suffered from overheating in hot weather. He has solved those problems but still
suffered from dreadfully hot feet inside the car! Here Gordon describes the measures
he has taken to improve the cooling of the engine in his MGBGTV8. (May
02)
The
cooling of the engine in the BGTV8 could only at the best be described as "marginal"
even when the car was first built, with new parts and factory tolerances. Now
that the BGTV8s are some 25 years old, things are different. Having covered over
200,000 miles in mine in the past 15 years I have had plenty of time to reflect
on the overheating problem and its causes, and have also experimented with cures.
So I hope that the following comments will be useful.
To
start with the basics, the engine is cooled by the thermo-convection of hot water
into the radiator where the through-flow of air reduces the water temperature
ready for re-circulation to the engine water jacket by the water pump. The velocity
of air-flow through the radiator will be a function of the system resistance -
if the air can escape freely from the engine bay, then there will be a high-speed
airflow and excellent cooling. Now the design characteristic of an axial fan,
whether electric or belt driven, is that it will deliver high volumes of air-flow
but only against low back pressure so the standard fans fitted to MGs are therefore
ideally suited to cooling the MGB and MGC which constitute low-pressure cooling
applications. Anyone who has looked at the V8 engine bay however will immediately
realise that one almost has to feel sorry for the air as it desperately tries
to escape from the over-crowded engine bay! Obviously and visibly the V8 engine
bay represents a high-pressure resistance to the air-flow so the design characteristic
of the axial electric fans means that they are basically unsuited to dealing with
it.
On the basis
that I feel we are starting from an unsatisfactory position and that all the correct
checks on radiator efficiency have been carried out, I offer the following suggestions
on how to reduce the anticipated overheating, arranged roughly in ascending order
of cost:
Thermostat
modification - take out the thermostat and remove the spring and working parts,
then replace the front disk; this guards against thermostat failure but also slows
down the water flow rate so as to give the water a better chance of absorbing
and carrying away the engine heat. If the thermostat is omitted completely, the
water flows too quickly to pick up the right amount of heat from the engine in
the Summer, whilst in the Winter the engine will take far too long to reach the
optimum operating temperature.
Remove
any RAC/AA/MGCC badges from the front grill; two of these plus the V8 badge
can disturb and reduce the area available for air-flow through the radiator by
between 15% and 20%. If badges are essential (including the V8 badge), then position
them behind the over-riders. Editor: Note there is now a smaller V8 Register badge
available as an alternative for the MGBGTV8.
Use
your heater - if you see the temperature gauge rising to unpleasant levels,
promptly switch on the heater fan, turn the windscreen heater control to maximum
heat and open the sun-roof and/or windows.
Fit
a an override switch in parallel with the fan thermostat (mounted on top of
the engine, near to the alternator) so that the radiator fans can be switched
on manually; as a standard practice in warm weather I switch the fans on as soon
as I enter a 30mph area. The switch, (I used a heater fan rocker switch which
also looks the part), has to be wired to connect to earth. The addition of a warning
light on the dash to show that the fans are switched on is a useful comfort factor.
Fit a yellow V8
fan blade or alternatively a standard MGB fan blade onto the existing boss
at the top of the alternator drive-belt system, preferably with a guard as it
will be rotating when-ever the engine is working.
Replacing
the V8 water pump - I find that the tips of the impeller blades on the water
pump wear quite | quickly
so that the water is not being circulated as efficiently as it should be. On high
annual mileage cars I recommend changing the water pump every 25,000 miles and
the improvement in cooling can be easily seen at each change.
Change
the existing 3-core radiator to a 4-core unit thus allowing more water to
be cooled by the air-flow. As far as I know there are no 4-core radiators available
off the shelf but a local radiator manufacturer can easily produce one using the
header tank, base, and side frame from the standard unit.
Make up
brackets and move the oil cooler to a position underneath its existing position
but mounted centrally behind the apertures in the front valance as on the R/B
V8s; the oil will still be cooled quite adequately but if you are worried then
move the number plate an inch or so higher. Moving the oil cooler will give a
20% to 25% increase in the air flow through the radiator. It is not too difficult
to re-route the oil pipes for the cooler and the standard oil pipes for the R/B
V8s can be easily obtained and used.
Fit louvres to the bonnet
as on the Morgan Plus 8. I saw an MGBV8 Roadster Conversion at the Abingdon Show
some years ago with two sets of louvres up the whole length of the bonnet as also
seen on the V8-engined Morgans.
Improved cooling fans. Some fans
are available from America using brushless DC motors with fan blades of a similar
diameter to the standard fans, but with 6 blades instead of 4. The blades on these
American fans are of a much better aerodynamic shape also they rotate faster that
our standard brushed fans so give greater cooling. The brushless electronic DC
motors offer virtually infinite life and minimal current drain, compared to the
standard fans which in my experience fail quite regularly and which draw 12 amps
when running. Incidentally these American fans are technically also a much better
design than the RV8 fans.
Fit the stainless steel exhaust manifolds
from the RV8 which exit via the side walls of the engine bay thus taking the
heat away more quickly, whilst the clearance holes for the manifolds provide additional
escape paths for the air-flow into the low-pressure area around the front wheels.
The standard manifolds (a) are of a poor shape, designed purely around the available
space in the MGB engine bay rather than focussing on engine efficiency and (b)
are made of cast iron which acts as a heat soak thus radiates heat very efficiently!
The RV8 manifolds join together near the gearbox with a balancer pipe, then a
single pipe goes to the rear silencer so there is no need to alter the fuel tank
position. This modification is very effective but is more expensive, as the manifolds
plus exhaust cost around £470, to which has to be added the cost of cutting
the holes in the inner wings, welding on the surround plates then respraying the
engine bay before fitting the system.
Following a recent drive to Sicily
in May 2002, then touring the island in temperatures of 30oC, I can confirm that
the RV8 manifolds are the complete cure to the overheating of both the engine
and the driver's and passenger's feet! Obviously in these temperatures I still
switched the fans on (using the override switch) for traffic delays or for climbing
serious hills. The only time I had to resort to switching on the heater as well
was when we climbed a steep mountain pass with 30 to 40 hairpins in the midday
heat.
Two other points - in hot weather the MGBV8GT footwell with
the standard exhaust manifolds always gives the driver and passenger over-heated
feet. To reduce this discomfort I recommend total insulation of the gearbox tunnel,
the floor, and the engine fire-wall with a flexible aluminium/mylar heat insulation
sandwich material obtainable from specialist suppliers such as Agriemach (Tel
01342 713743). Agriemach also supply a special asbestos-type material for wrapping
around the exhaust manifold which is very effective. Conversely in a spell of
really cold winter weather the warmth inside the cabin can be greatly increased
by removing the steel cover from the brake and clutch cylinders - provided you
are sure that there are no leaks from the exhaust manifolds etc!
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