Workshop Ramblings

by John Murray

You might recall from the April TTT 2 that John is the chap who was driven to despair by the DVLA when he contacted them and tried to put right some incorrect record details they were showing for his TD.

One of the great things I love about T-Types is there’s always something to do.  At least that’s what I tell the wife!  Although TD8205 is in really good order, I wanted to address a few things to, (in my opinion), make improvements.  These were:

Change over from Positive to Negative Earth – Reasons; makes it safer and easier to use GPS, USB devices, chargers etc.  Well, those of you who have teenage children or grandchildren will know that they must be “plugged in” at all times to their various IT devices!  I’m just happy that they want to go out in the TD.  Also, things like electronic ignition mods are cheaper for negative earth.  That’s my Scottish/Yorkshire heritage showing.

Fit Electronic Ignition – What I still call “contactless ignition”.   Hopefully, this will help my ageing DKY4A distributor.  Unlike the lucky MGB owners who can purchase a complete electronic distributor/ignition coil kit for under £100, these are not yet available for the older model ‘dizzies’; at least at prices under several hundred pounds.   (hint to suppliers/manufacturers).  Another reason for the change is that the original capacitors/condensers are no longer available and there are numerous reports of the unreliability/failure of modern replacements.

Replace the now unobtainable external can oil filter.  Mine is a very early TD which has the TC style can type filter.  In fact, a lot of TD8205 is TC including most of the wiring!

Now for some notes on what I’ve done, starting with +ve to -ve;

The change over from positive earth is very straightforward and is detailed in various manuals and of course, on YouTube if you’ve never attempted it.  In summary,


Disconnect the supply to the fuel pump – I’ll explain why later.  But do it!

Disconnect the battery leads and swap the battery around so that the terminals are now located in the opposite sides.   Reconnect the leads.  Note: some battery posts are slightly different sizes but the connectors should expand enough to fit ok.  Take the opportunity to clean and grease the terminals.

Now we need to “flash” the generator.  Not as dramatic as it sounds.  We simply need to reverse the field polarity of the dynamo.  Easiest way is at the voltage regulator.  Take a small jump wire and BRIEFLY touch the battery positive terminal and generator field terminal, (usually the A and F terminals), together.  There should be a small spark.  You only need a brief touch.  Don’t connect for more than a second or so.  That’s it for the generator.  Moss Motors Help Center have an excellent video tutorial:

At the ignition coil the +ve and -ve leads need to be swapped over.  The -ve is the one that goes to the distributor in the original configuration.  Just simply swap the leads.  It will not harm the coil but will ensure the charge/discharge cycle is correctly polarised.

Now for the fuel pump.  Depending on the type/model a little investigation is required; you may or may not need to reverse the supply leads.  Early type SU pumps with contacts are not polarity conscious.  Later models are.  Solid state pumps should be marked.  I have a German solid-state pump – I hate SU’s with a passion!! – and had to reverse the supply.  Do check as a burned-out pump can be expensive.  Hence my earlier comments.

Lastly, swap the leads on the rear of the ammeter.  If you want to leave this step for now it will not harm the meter but the needle will simply show a discharge when the engine is running.  The ignition light should go out when you start up.  That’s all there is to it.

No, the starter motor will NOT run backwards and you will not have one forward and four reverse gears!

Having successfully changed the polarity of the car, I turned my attention to fitting electronic ignition. The first couple of pictures show the existing set-up.

PIC 1:  DKY4A distributor in its ‘lair’. The top of the oil filter conversion can just be seen.

PIC 2:  Cover removed to show standard points arrangement.

I purchased a kit from ‘AccuSpark’ for just under £40.  There are other suppliers but his reviews are good and he does a good video on how to install and set up the kit.  The instructions supplied are very concise and easy to follow and as I found, technical support is good.

PIC 3:  Points removed and alongside the AccuSpark kit.  Essentially, it’s a “Hall-Effect” device.

Only the two small outside screws need be removed to take out the whole points assembly.  As can be seen from PIC 3 the kit replaces the whole points baseplate – nice and easy!

PIC 4: Base plate in situ.     

PIC 4A: With “actuator” ring and rotor fitted.

Clean up the distributor cap, or fit new if desired.  Now connect the two leads, one red, one black, to the ignition coil.  The red lead goes to the positive terminal and the black to the negative.  The standard coil will work fine.  It should have a resistance of about 3-4 Ohms which is ideal to work with the kit.  If you want to check the coil resistance, do it with all connections removed.

To be honest, I hit a snag with the actuator ring supplied – it wouldn’t fit.  The instructions say to trim any excess with a craft knife but, in my case, it would have been far too much to remove.  A quick call to Chris at AccuSpark and he sent me down a kit of three rings within 24 hours at no extra charge.  One of these fitted perfectly. 

Note:– there are at least three different cams fitted to the DKY4A distributor.  Guess who had to have an awkward one!  The gap between the actuator and the sensor is not critical just as long as there is one.  Mine was about 8 thou.  (I’m sure there is an anorak out there who can convert that to tiddlywink S.I. units).

The moment of truth.  Start the car; well bless her, she started first time!  Didn’t run very well – but at least she started.  Now the timing bit.

These kits can only really be timed properly with a timing gun/strobe.  I found my timing had moved from + 10 BTDC to – 8 ATDC and TD8205 wasn’t happy.  Switch off, slacken the distributor clamp and move it clockwise a ‘snadge’, (technical term for just a little bit).  Start up and check with the timing gun.  Better.  A ‘snadge’ more and we were at +10 BTDC at about 800rpm and TD8205 was running sweetly.  I find she likes that setting with unleaded fuel; yours may differ slightly.  Turn the distributor clockwise for advance, anti-clockwise for retard.

PICS 5, 6 & 7 show the timing pictures, I’m lucky that my gun gives me a digital readout of angle and rpm.

Above: PICS 5, 6 & 7.

A test drive was very satisfactory with good performance and dare I say it, no issues.  More testing will of course be necessary to determine overall improvement and any changes in fuel economy.  At least that’s what I told the wife!

I was impressed with the service from AccuSpark and with the quality of the parts.  It ‘did what it said on the tin’, as they say.

Oil Filter Conversion.

A service of the engine revealed that the old external canister filter was made in the USA and so at a guess, had been on the car for probably 3 years before I purchased TD8205.  OK, so it hadn’t covered much mileage, but even so, it needed changing.   As stated, these archaic beasts are apparently now extinct.   Research showed various options, some rather expensive!  I eventually found that Roger Furneaux down in the West Country, does make a limited number of units machined from solid aluminium that allow the easy fitting of a standard 3/4″ spin on filter for about £80.

Ed’s note: Also available from MG Octagon Car Club (you need to be a member) and NTG Motor Services.

Oil filter adapter TB/TC and Early TD.

As can be seen, it’s a nicely made unit that fitted perfectly.  It took me longer to source the correct copper washers for the banjo fittings than for Roger to supply me with the unit.

TIP – if you have to re-use the old ones, (not recommended), then anneal them first with a blow torch – GENTLY!   It softens them so that they swell slightly and are less likely to leak.

Bear in mind that they have to withstand up to 60 psi of engine life blood.  Any serious leaks here can be catastrophic!  Having seen a high pressure leak I can assure you it comes out fast and the cleanup takes ages.  I’m not a great fan of the idea of an external filter hanging on a clamp and two feed pipes.  The thought of paying for a new engine if one lets go doesn’t bear thinking about.  Yes, there is a pressure gauge on the dash but, most of the time my eyes are on the road.  Would we see it drop to zero in time?  I doubt it.

OK so it’s non-standard, but TD8205 is not, and in my ownership, never will be a trailer queen. There are times when practicality and prudence rules.  Being able – at my age – to simply remove and spin on a new filter without resorting to ramps and a hoist – that’s for me to get up – is bliss.

One thought on “Workshop Ramblings

  1. Martin van der Merwe says:

    Could I ask whether the oil flow in the conversion is correct, ie. that the outlet connection reports to the center of the filter itself? An acquaintance had an early cast aluminium conversion that had taken the easy way out and plumbed the top connection to the center of the filter. Unfortunately, the filter had a check valve and there was therefore no oil flow. Even if the filter did not have a check valve, these paper element filters have a support mesh for the paper. If the flow is reversed the convolutions in the paper are pressed together effectively collapsing the filter and resulting in near total blockage. Fortunately, the XPAG blocks have a filter bypass allowing continued lubrication.

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