OUT WITH THE 6LX – IN WITH THE O.680
West Midlands PTE had a particular fetish for
Gardner engines, and when supplies dried up
temporarily in the mid 1970s it had to turn to the
only real alternative for a couple of batches of
Fleetlines, 4530-4579 (GOG530-579N) in 1975
and 6301-6420 (KON301-375P, NOC376-
420R) in 1976.
This was the 11.1 litre Leyland O.680 (‘O’ for
Oil), which was slightly higher rated than the
Gardner 6LXB at 185bhp. A familiar engine in
such as Leyland Atlanteans and Leopards, the
O.680 was a newcomer in PTE buses, earlier
new and second-hand Atlanteans, and the ex
Midland Red LS18 Leopards having the smaller
capacity 9.8 litre O.600 unit. Perry Barr and
Yrdley Wood shared the 45xx batch (two BCT
garages with a Leyland history, having earlier
shared all the Brush bodied PD2s, 1656-1755)
while the second batch was concentrated on
ex-Midland Red, Walsall and Wolverhampton
garages. By all accounts, the engines
themselves performed very well, and the drivers
liked them because they were marginally more
powerful and had a lighter accelerator than the
Gardner engined buses. Nevertheless, there
were quite a lot of failures of fan drive shafts
and couplings, which led – it is believed – to a
modified arrangement. However, as time went
by and the Gardner supply situation improved,
the Leyland engined variety were viewed as
being non-standard, and a programme of
replacement of the engines was embarked on,
using mostly 6LX (150bhp) units from earlier
withdrawn Fleetlines.
The conversion jobs were carried out at works
at Walsall and Coventry mainly, and the last
few Leyland engined buses lingered on in
service until the early 1980s.
The Museum had acquired Fleetline 6311
(KON311P) from WMPTE in 1989. The bus
spent many seasons in use on open days etc.,
but in recent times had started emitting more
and more smoke, and investigation revealed a
fault on one of the front cylinder head rocker
shafts, which would have meant a replacement
cylinder head being fitted. Latterly it was
dropped from use pending repairs.
For a long time, many people had remarked
that it would be nice one day if the Leyland
engine could be re-instated, and although an
appropriate engine had been sourced a while
ago (taken from a WMPTE ‘CRL’) the task of
converting it back was seen as a ‘big’ job, and
so was not high in priority. It wasn’t really
known if the conversion back could be made
realistically.
Late in 2005, an ex London Transport ‘DM’
(part of the DMS Fleetline family) appeared on
internet auction site ‘E-Bay’, a former
Kettlewells of Retford vehicle, used as part of
their school bus fleet. The attraction of GHV67N
was mainly for its Leyland engine, which being
a known quantity would in theory be a better bet
than the long time stored ex WMPTE engine.
The bus was bid upon and secured and, being
a runner, was driven back to the Museum. This
coincided with an open day, and as space was
limited it was initially put on the pit inside the
workshop.
This was to prove fortunate, as the engine was
left running for a while, and it was noticed after
a while that there was oil spraying onto the
ground beneath the flywheel. Although the
engine was ‘breathing’, a sign of perhaps high
mileage, it ran very smoothly and quietly and
with no visible smoke from the exhaust. By
now, excitement was mounting, and the
question once more was, could the conversion
of 6311 take place? 6311 was studied in detail
and it was decided that it could be done, with a
few reservations regarding ancillary
components. But what of the oil leaking from
the donor engine – was it flywheel oil or engine
oil?
With the open day over, GHV67N’s engine was
run up to operating temperature and, sure
enough, the leak returned. Close examination
suggested the rear crankshaft seal had failed,
and there was some disappointment. However,
despite this meaning extra work dismantling the
engine once it was removed, it was felt work
should still go ahead. And so more or less
straight away, over the next week, GHV67N’s
engine came out first, followed by 6311’s faulty
Gardner. Luckily, the Museum owned the
correct lifting bracket for the Gardner, but a
system of hooks and chains had to be
employed for the Leyland, in conjunction with
the sturdy hand crane.
The flywheel was dismantled on the Leyland
engine and the backplate removed. This also
necessitated removal of the sump, to get at the
two-piece housing containing the two halves of
the felt crankshaft seal. Although spare parts for
O.680s aren’t too common these days, a set of
the required seals, gaskets etc., was obtained.
Whilst the sump was off, the lower end of the
engine was examined, and we were horrified to
find that the castellated nuts at almost every
con rod did not have a split pin present. The
remaining ones were the wrong size and much
too small. So it looks as though the engine has
had previous attention, with someone not doing
the job properly. The tightness of the nuts was
checked and the correct split pins refitted. The
sump, backplate and flywheel went back on
(including a new bearing in the latter) and
attention turned to other items needing work.
The water pump was very noisy with worn
bearings, and a replacement was fitted, along
with new fan belts. All water hoses and clips on
the engine were replaced, and the accelerator
system on the engine also had to be converted.
Originally air operated, the hydraulic system
would be reinstated, removed from the spare
engine. Whilst doing this, the opportunity was
taken to change the water jacket gasket on the
cylinder block, which the accelerator bracket
bolted onto. On closer inspection it looked as
though it had been leaking for some time. New
engine and fuel oil filters were fitted, and the
tappets adjusted.
Fortunately the engine mountings front and rear
were the same as on a Gardner, with only the
rear chassis brackets differing. These were
swapped over and new mounting rubbers
installed. A mismatch of threads between the
compressor air pipe and the chassis pipe
connection resulted in a bespoke flexible pipe
being made by hydraulic specialists Pirtek in
Oldbury (at a high cost!). Fuel supply and return
pipes Luckily had the same threads making
things easier.
On a Gardner engine, the alternator is mounted
on the front, and the starter on the rear,
whereas the Leyland has a front mounted
starter and the alternator is mounted on the
gearbox and driven by a belt off the fan drive
shaft. This would cause problems with the
associated wiring, and Jeremy Price was
enlisted to re-route, lengthen and shorten the
wiring looms as necessary. Whilst the engine
was out, the opportunity was taken to renew the
gearbox output seal, which had been leaking
previously for some time.
Things were starting to take shape now, and a
lot of the problems overcome. With an empty
engine bay, Tom Couling gave it a good clean
down and paint, and Kevin Hill used up some
green paint and sprayed the engine. One final
problem was the exhaus t system; again a
discrepancy, this time the differences in bore
size. Fortunately the boltholes in the Leyland
engine’s flexible pipe withstood opening out and
with a new gasket was successfully matched up
the to the Fleetline’s existing ‘U-bend’ pipe.
As the donor bus had fluid power steering, and
the recipient didn’t, the drive off the engine had
to be blanked off. The last two jobs were to
convert the gearbox drive coupling to accept
the differing type fitted to the Leyland, and
exchange radiator/fan drive assemblies. At last
it looked like the engine could be refitted.
With extra helpers and watchers, the day came
and the replacement engine was fitted in with
very little fuss. A day or so was spent reconnecting
everything and refitting the radiator.
Late one night the moment came to press the
start button and see what happened. The
engine started without hesitation. but would
only run for a few seconds before stalling. A
fault in the fuel filter head was traced and put
right, and – Bingo! – the roar of the mighty
Leyland O.680 could be heard once more from
6311, much to the delight of all those present!
Over the following few days the engine was run
up and checked over for any leaks etc. A few
minor fuel leaks were solved and 6311 was
insured for a week so that a proper road test
could be undertaken. On the day 6311
performed quite well, with only a water leak
from the new water pump gland, but this
subsequently sealed itself with more running
and is OK now. The accelerator system on the
Leyland engined Fleetlines was much lighter
than on a Gardner, this being down to a
different design of fuel pump on the engine.
However, the pedal felt a little too floppy, and a
faulty master cylinder was suspected. Upon
return, this was checked over the pit, and the
cylinder found to be leaking. Once changed, the
pedal improved and there was a noticeable gain
in performance too.
6311 was left running for a while, and then
another water leak unexpectedly appeared, this
time from the other cylinder block water jacket
gasket. This proved to be awkward to rectify as
to remove the jacket, the compressor and fuel
pump would have to be taken out, or so we
envisaged. After some thought, and the cutting
down of a certain stud in the compressor, it
proved possible to remove the cylinder head
and cylinders off the compressor with it still in
situ. A new gasket was made and the jacket
resealed, and the leak was stopped.
The engine swap had taken took just four
weeks of intermittent work. Now that 6311’s
major transplant was complete, it was decided
to get it ready for a Class 6 Test, for use in
2006. The rest of the bus was checked over
and a list of jobs made, which are being tackled
as time permits over the winter. A lot of the
lower saloon seat frame legs are very badly
corroded, with two found to be broken. Pete
Murphy is tackling this job. All of the saloon
heater motors were found to be seized up, and
replacements have been fitted. All being well,
6311 should hit the road again this year and
despite having a workworn and slightly ‘weary’
engine, should prove popular with enthusiasts
keen to sample a Fleetline with something other
than a Gardner engine!!
MP
Chapel Lane, Wythall, Worcs B47 6JX
Tel : 01564 826471 e-mail us
A registered educational charity no 507191
