----- Original Message -----
From: Scott Beavis <sbeavis@solartron.com>
To: _MGs <mgs@autox.team.net>
Sent: Wednesday, August 23, 2000 11:15 AM
Subject: Closer look at new MG engine bits
> One potential problem here is the coil is a 6V ballasted type. I
> can't see a ballast resistor anywhere. Anyone know where it may be
located?
The ballast is a length of resistance wire contained within the loom. It
starts off as a white/brown at the fuse-block/ignition relay and ends up as
a white/light-green at the coil and from there to the solenoid.
> The engine is still coughing a bit when accelerating in 3rd gear.
> It seems better with full choke so I still think the carbueration is all
> cock-eyed. I'll 'colortune' it and see what turns up.
Flame suit on, but the ColourTune won't help you balance the mixture unless
you have two in different cylinders or keep moving it from 1 to 4 and back
again. The twin SUs are interdependant and when you adjust one you have to
recheck the other and keep doing that till both give the correct conditions,
which is best judged from the lifting pin. If you choose to (and for your
year I suppose it would be advisable) you can then adjust *both carbs* in
the *same direction* and by the *same amount* to get the required reading on
a Gunsons CO meter at the tailpipe.
> As for this 'expansion bottle' I stuck a finger inside and discovered it
has
> a pipe leading to the bottom, so not as bad a design as I though. The
> trouble with this system is it is more of a 'replenishing reservior' than
an
> expansion tank. It will let steam out and then suck water back in when the
> engine cools. This is ok, so long as you switch off every now and again.
> Long journeys could see the coolant level in the engine dropping. A
'proper'
> system has two pipes to the engine so that water can top up the engine
level
> at any time. The steam then leaves the system via a balance pipe to the
top
> of the expansion bottle, and if pressure gets up the cap vents. This is
how
> it is done on most 'modern' cars including metros 1980'ish on. This would
> have the advantage that the engine was always 'underwater'. It does
however
> require the expansion bottle to be mounted above the cylinder head level,
> which my be a little tricky.
With the MGB you fill the system through the radiator or thermostat housing
and this keeps the engine fully 'under water'. As the water heats up it
expands into the tank (hence 'expansion tank', and taking any air bubbles
with it since the pipe is at the highest point) with the pressure cap and
compresses the air in there - hence it should not be more than half full
when cold. When the engine cools and the water contracts it sucks it back
in from the expansion tank. There shouldn't be any steam in the system -
the pressure cap prevents any boiling - unless there is a fault. The only
way water level can drop on long journeys (or at all) is you have a leak.
Modern cars are something else, don't forget you are talking 25-year-old
technology here, and it works just fine.
> Another thing I noticed is that the pipe to the oil pressure gauge looks
> like it's on it's last legs. I'd like to fit a nice braided hose. AFAIK
the
> gauge is the original. Are they smiths fittings? or Tim type? I expect the
> block thread is the same as on the A series (1/8" NPT I think, or maybe
> BSP). Is it difficult to get to the back of the gauges? Does the dash
simple
> unscrew and pull out, or will I have to work blind feeling up the back?
Don't know about fittings. The dash does NOT simply unscrew and pull out
(that is, it does unscrew and pull out, but not simply). Depending on the
size of your hands it is relatively easy to remove the centre air vents and
reach in there and up behind the dash and remove the gauge fixings, ease it
forward and disconnect the oil pipe from the back of the gauge. There
should be a bracket securing the pipe to the heater box - watch out for that
before trying to yank the pipe out.
PaulH.
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