Simply put, to turn your classic car from a manual gearbox to an automatic you just need to find the right parts. If the car in question had an option for a slush box, then all the better. But why bother? Sure, if you wanted to shoehorn more horsepower into a British classic relatively cheaply, an automatic box will take more torque than its manual equivalent. The Marina auto versions were all low compression engines, denoted by the ‘L’ in their engine number. With the low-down torque these engines make the automatic box is very well suited and can transfer this into a very well-mannered car around town, but still kick down and pull hard when provoked out on the motorway and B roads.

These conversions seem to be carried out as a necessary evil, rather than an upgrade to an already capable car. Owners often want to keep their pride and joy, but may feel strain when using the clutch – switching to an automatic means they can keep the car but drive it in comfort.

The car we converted is a manual spec Marina HL but all of the steps are for 1800/1300 single and twin SU cars.

Parts for these are no longer off the shelf, so it is vital to make a list of what is needed before striping your car of its manual box. I’ve heard of complete cars being pillaged for their autos, linkages and connections – but this really isn’t necessary if you know what, and where to look for it. For example, the Marina auto engine is identical to any other Marina with a manual transmission – and it is more than possible to add an automatic to a high compression engine. The low comp engine would work better with the torque converter, making better use of the power, but all that is needed would be a set of LC pistons should you want to go this route.

Parts required for 1800/1300 auto conversion

Auto box/torque converter:

Borg warner 35 (mk1 ->73) or Borg warner 65 (mk1 73->, mk2, mk3 and Ital) – Boxes are available both new and second hand via Club contacts.

Flex plate

Made up of a starter ring gear and round plate welded and balanced. Certainly something that a good machine shop could make up or available through Club contacts.

Selector and linkages:

Ok, so technically these are only available on Marina automatics – but when you look closely you could make something up from various BL cars of the era. For example, have a look at small triumph cars of the 70s such as the 1850 Dolomite as it may be in better supply through Triumph specialists. The selector rod is only a piece of steel rod with a threaded end and adjuster linked onto it – something that could be made up with some hand tools, a pillar drill and a tap and die set.

Engine back plate

On the automatic version there is a 1 ¾” round hole that sits between the sump that allows access to the torque converter bolts when the box is in the car. If you don’t have an auto back plate simply measure up the distance between one of the bolt holes on the flex plate and the back plate, then use a pillar drill and hole saw to open up the plate.

Crank spacer

Now this part is what allows the flex plate to sit out further from the end of the crank and centres the starter ring gear with the starter motor – a rare part but if you are serious about making an automatic Marina the Club can have one machined up for you (P.O.E)

Spigot bush

Removal of the bronze bush is required before fitting the crank spacer.

Kick down

This function not only allows the box to drop down a gear when the accelerator is pushed to the floor, but monitors the location of the throttle position and makes the box change down correctly – A kick down that is incorrectly fitted or missing will mean the box will not function as designed. The bracketry for the Marina is simply made up by an angled metal edge and crude connector on the end of the rear SU carburettor. For our conversion we had to guess as at the time we couldn't find an accurate diagram – whilst it is crude, it allows the accelerator to operate between idle and wide open throttle and kick down to work as designed.

Inhibitor switch

Part number: DRC2918 – same as Rover SD1 and London taxis!

 

Inhibitor wiring

The Marina wiring for manuals is identical to the autos. The only difference is a connector block that sits under the heater box. On the manuals it has a loop for the starter circuit, and on the auto it connects into the inhibitor. Three cables needed here and a connector. Available from many auto spark companies.

Prop shaft

Identical to the manual version

Gearbox mount

Identical to the manual version

 

In conclusion

So, before you venture into buying a complete Marina auto to convert your classic, be sure to contact the MMOC & IR to see if we can help you. Marinas and Itals are in limited numbers and we are committed to help new and existing owners keep these cars on the road for future generations.

 

 

 

 

 

 

Our car:
engine type     naturally aspirated petrol
engine manufacturer  Morris
engine code 18V
cylinders          Straight 4
capacity           1.8 litre 1799 cc (109.782 cu in)
bore × stroke   80.26 × 88.9 mm 3.16 × 3.5 in
bore/stroke ratio        0.9
overhead valve (OHV) 2 valves per cylinder 8 valves in total
maximum power output (din)    86 PS (85 bhp) (63 kW) at 5500 rpm
specific output (din)    47.2 bhp/litre 0.77 bhp/cu in
maximum torque (din)    135 Nm (100 ft·lb) (13.8 kgm) at 3000 rpm
specific torque (din)    75.04 Nm/litre 0.91 ft·lb/cu3
compression ratio       9:1
fuel system     2 SU carbs
bmep (brake mean effective pressure)         943 kPa (136.8 psi)
engine coolant            Water
unitary capacity          449.75 cc
aspiration        Normal