jvr@pclink.com wrote:
>
> >
> > >
> > > Hi,
> > >
> > > I hope someone can help me with this one!
> > >
> > > I just purchased a 75 Midget (no rust) and as part of fixing the
> > > mechanicals I noticed it has no vacuum advance on the distributor.
> >
>
> Hi,
>
> Thanks for the reply!!
>
> > Your 1975 Midget, should be a 1500 Midget with the Triumph engine.
>
> It is.
>
> This
> > used a Lucas 45D4 distributor in the UK. For North America it should
> > have an electronic version, 45/DE4.
>
> It doesn't have the electronic version, it uses regular points and
> has no electronic ignition module.
>
> Inside it is virtually the same
> as
> > the normal points version 45D4, using weights for the advance and a
> > vacuum capsule. There is a slot in the side of the body for the linkage
> > of the vacuum capsule to connect to the baseplate, it seems your entire
> > vacuum advance is missing.
>
> Yes it is missing and there is no slot for the linkage.
> >
> > BUT WAIT..........it is common to remove this system of advancing the
> > spark on engines used for racing, as it is an ECONOMY measure. Infact
> > many Sprite Mk4 and Midget Mk3 DO NOT have it fitted, ( 1275cc 'A'
> > series engine.) Check the spec of your engine, you might have a hot cam
> > and bigger valves in it!!!!!!!!!!
>
> Interesting, how do I check for the hot cam and bigger valves without
> dissassembly?
>
A) Check how far the valve rocker 'lifts' the valves. Do a compression
check, though if its a wild cam, this can be LOW at idle rpm. Best way
is to carry out the valve timing check as per the manual.
> >
> > OR.....has some one fitted a normal points distributor to your 1500?
>
> Normal points alright.
>
> Is my memory correct that vacuum advance only works at low or idle
> RPM and centrificul advance works for RPM above that?
>
A) The vacuum 'advance' works at idle, and on lifting your foot off the
pedal, ( over-run.) It was deleted from the 1275cc Midgets as it could
cause too much advance in the wrong place.
> What effect if any would not using vacuum advance have?
A) You will not notice it is missing, BUT YOU MUST ensure the baseplate
is not swivelling about free....ie doing its own thing as far as
ignition timing is going. The distributor should have the correct
baseplate fitted....one that CANNOT move!!
>
> Would it be worth fitting the 45DE4 distributor from my 78 donner
> Midget to the 75? Where would I rob the vacuum from to use with the
> 45DE4 and is the amount of vacuum critical?
A) I would not bother with the vacuum advance at all, personally. Moss
will sell you any bits you need.
> BTW what about EGR? My EGR valve is frozen shut so there is no
> exaust gas injected into the intake manifold. What, other than
> raising the pollutants, is the disadvantage of not fixing this
> problem?
A) ERG ( Exhaust Gas Recirculation, ) was found to reduce peak
combustion temperatures, and by doing this reducing the NOx, ( nitrogen
oxides.)
In the USA it may be very necessary to have it fitted to pass the Clean
Air Act pollution levels, ( someone listed these figures recently in
this list.) You will actually gain a tiny amount of power by not using
it, if you remove the thing, plus a very small extra miles per gallon.
>
> THANKS for all your help,
>
> Dick
> >
> > Neil, [always ready for any interesting faults!!! MG engines a speciality,
>( got my book yet?)]
> >
> >
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