Fitting a 1275cc Metro Engine

I have often written upon the subject of the interchangeability of components within the family of cars of the Nuffield, BMC, BLMC and Austin Rover. One of the good things about models running on for years is that the spares availability is often excellent. One little car that spawned a huge cloning operation by other world car producers was ADO15, the 1959 Mini. ADO stands for Austin Design Office. It had stolen its engine and gearbox from the 1952 Austin A30, by way of the improved 1956 Austin A35/40. Alex Issigonis got the engine department to put the engine on top of the gearbox's innards, with a nice new aluminium casting to fit them all into. It was not long before the 1098cc Austin 1100 arrived, called the ADO16 also front wheel drive ( fwd, ) and using the very same engine and gearbox unit. Well, almost, the stroke had been lengthened to get the extra cubic capacity. This soon grew to 1275 cc with the bores being offset to get them into the cylinder block. Other models in the BMC range using the 'A'series engine had also been updated, such as the 1098cc MG Midget and Morris 1000. In 1966 the Midget grew to the 1275cc with the ADO16. The rear wheel drive ( rwd, ) cars had different blocks and crankshafts to the fwd cars, but many other engine castings and internal items were common to all of the models. Amongst all these models was the MG 1100, the single carburetter MG 1300 Mk1 and the twin SU MG 1300 Mk2. The 1300 Mk2 was a very good car, as the 70bhp power output of the 1275cc engine it had was more suited to the heavier body of the ADO 16 over that of ADO15, the Mini. It has to be said that the original MG 1100 had its work cut out to give a sporting performance. The 48bhp 1098cc engine had to rev very high to give a good cruising speed, making the car look as if it were being thrashed all the time.

Time passed and the models were replaced. All except the Mini. This was updated little by little over the years, until it found itself running alongside the 1981 Austin Metro, ADO88, later called the LC8, ( Leyland Cars.) This Austin car was built with a 998cc and 1275cc engine. Both engines were also used in the current Mini. To keep costs down, the power unit castings were the same. That is, the aluminium gearbox casting in the 'A' plus fitted Mini 998cc, 1275cc, the Metro 998cc and 1275cc, were identical. But both cars used different engine mounts. This was got round by the Mini mountings being the standard fittings, with the Metro ones bolted to suitable bits of that casting. So, a Mini engine can be put into a Metro, and vica versa as long as you swap over the relevant items. Note, this is the 'A' Plus 'A' series engine, all post 1981 because the earlier 998cc and smaller capacity engine size gearbox castings need metal grinding away, to miss the larger crankshaft throw of the 1275cc engine..

Then in 1982 the MG Metro 1300 came along, with its 72bhp 1275cc engine, based on the 50bhp Austin Metro 1.3. Then the MG Metro Turbo arrived with its 93 bhp 1275 cc engine. Remember that the 1100/1300 used the basic Mini engine castings. Well, you can quite easily fit a nice MG Metro 1300 to any of the 1100/1300 range, with a few simple spanner modifications. Because the basic design did not change so radically, a 1989 MG Metro 1300 engine can be put into a 1962 MG 1100. You do not have to use a rusted out MG Metro engine, you can used the Austin 1.3 GTa, or even the cooking Metro 1300 and Mini 1275 engines. Using a cooking 50bhp 1275cc Metro engine would need the relevant camshaft, distributor, and larger exhaust valves fitting to get up to 72bhp. Here companies like MiniSport will be only too glad to help. Interchangeability is the secret and this is due to the fact BMC, BL, and Austin Rover were too tight fisted to spend money on new production machinery for the Mini. 'If it ain't broke, don't fix it.'

So, how do I get a 1275cc Metro engine into my MG 1100? And why bother? First, you can pick up rotted out Metros with good engines for less than £200, as Mot failures they are even cheaper. This is about one quarter the cost of fully rebuilding an original 1100/1300 engine.

As the Metro's clutch cover casting has the Mini engine mounting holes drilled and tapped, you can fit the 1100 engine offside mounting without any problems. The later Metros had a cable clutch, but the slave cylinder from a post 1981 Mini will fit the same bolt holes as your MG 1100/1300. You can even fit your current clutch slave cylinder if you swap over the actuating lever arm. Note that these later 'A' series engine have Verto clutches, so you need to use the clearance adjustments for the Verto fitted Mini for the actuating rod. You can remove all the Metro engine mountings as they are not required. You will need to also removed the fan belt pulley, timing chain cover, timing chain and sprockets, from both the Metro engine and the 1100/1300 engine. Then swap over the front engine plates. That on the Metro has no side arms for the 1100/1300 near-side engine mountings. This plate is the same as that fitted to the Morris 1000, Austin A40, and the 'A' Series fitted MG Midget. So are the engine mountings. Refit all the Metro's own timing chain, sprockets, cover, etc. but when you come to fitting the timing chain tensioner, you will need to drill a 3/8" hole to clear the pivot of the tensioner. Use the original Metro plate as a template. If you have a double-row timing chain, you will also need to countersink the two lower holes, for the heads of the two screws that hold the plate to the front engine main bearing cap. If you fit the normal headed bolts, the chain binds on them. Again this is obvious if you study the two components prior to assembly.

The Metro has more modern universal joints in its inner drive shaft ends than the ADO16, but you will need to use your current MG 1100/1300 shafts. And you will need your current drive ratio, (unless the Metro one suits you.) This means swapping over the differential, but here you can get away with just swapping the planet-gears inside it, that the drive shaft inner ends locate into. Ideally you want to end up with your normal 1100/1300 drive shafts being able to connect to the engine, for this you need to put the bits out of your original engine into the Metro engine. Again comparing the two next to each other makes it easy to decide what needs swapping between the engines, and it is only spanner work. Swapping final drive ratios is easy on this engine layout, any Mini manual will show you how.

Next the cooling arrangement means you will needs to connect the MG Metro's thermostat bleed to the inlet manifold, and the other end from the manifold to the rear of the cylinder head. The Metro uses a water heated inlet manifold. >From this you will have to adapt a feed for your heater. The Metro uses a heater that has a hot water flow all the time, the 1100/1300 can close off its water flow. The 1300 Metro has no by-pass hose between the head and block, that function is carried out by the heated inlet manifold. You will see that the thermostat housing has an additional casting under it for the hose connection to the manifold, (on the Metro this goes to the heater, then manifold, then the rear of the head.) The MG Metro has a single, huge SU HIF44, (the 1275cc Mini has a smaller SU HIF38) The inlet manifold is easy to fit, but you must keep the twin cast iron exhaust manifold as it boosts BHP. You will need to adapt the front exhaust pipe to your current 1100/1300 exhaust system. Brackets to support the radiator can be swapped over from the old engine.

Post 1986 MG Metros also use electronic ignition, all have alternators and four speed all-synchromesh gearboxes. The later ADO16 1300s used the rod gear change as well, so that of the Metro should be adaptable for earlier ADO16s. The MG Metro's large single SU carburetter is much easier to keep in tune than those twin SU's of the MG 1100/1300. As there is so much room in the 1100/1300 engine bay, who will be the first to fit an engine from a Mot failed MG Metro Turbo?

Once a MG Metro 1300 engine ( or upgraded Austin Metro 1.3 engine, ) is installed correctly into an AD16, the vast majority of enthusiasts would be very hard pushed to identify it as anything other than the original. The better informed will soon spot that single carburetter, but with 72bhp at hand you will fly. If you use the MGs large plastic air filter, the car will also be very quiet as intake roar is killed off. Be a bit suspicious about that immaculate 1962 MG 1100 that just cruised past you at above the legal speed on the motorway, four up!