Article on The Internet Mini Encyclopædia
Metro engine compression ratios
From the Metro HBOL:
Compression Ratios (Early Models:)
Low Comp. (1.0l inc Van) 8.3:1
Std Com (inc 1.0l and gala) 9.6:1
High Comp (inc L, HLE and City X) 10.3:1
From then on it goes by engine number, but the three comp. ratios are quoted for the entire lifespan of the metro range, including Unleaded models.
Metro engine upgrade
What problems will I encounter when I put a 1275 metro
engine into a mini and how much will it cost.
WARNING!!! Don't even consider doing this unless you have at least 7.5" discs. More than a 998 and drums are Dangerous!!!
You will need;
1) An engine!!
An MG metro engine is ideal but you will pay more for one of these. The next best is a Vanden Plas these are the same engine but with lower Compression Ratio (9.4:1 instead of 10.5:1). Then you have the Standard 1.3 metros in all sorts of forms. For more details on this sort of thing go out and buy the Metro Hynes Manual, it has lots of bits that the Mini manual misses out about the A series.
That is from a pre 86 Car so it has an Hydraulic clutch. It must also have a blanking plate on the cylinder head where the heater tap fits. VERY early Metros had Non Verto Clutches. (1980 ish)
The Price of engines varies A LOT but don't pay more than 150ukp. If you have the space try and find an MOT less MG metro This will get you a decent pair of seats and a pair of 4 pot callipers.
If you are planning to get even more power get an MG Metro Turbo engine. This engine is quite a bit heavier. It has a stronger gearbox, stronger clutch, stronger crank etc so if you are planning to re-bore for even more power then this is the engine to look out for.
With engine bay modifications the Metro turbo engine (including turbo) will fit but this starts getting complicated. It is this set-up that the ERA turbo mini uses.
Don't even think of using the std. Mini Exhaust, manifolds and Air filter . Buy a 1275-stage1 kit this will cost about 150ukp. If have an MG metro engine then use it's inlet manifold.
NEW std radiator 40ukp or an uprated one 60ukp
An Ultimate engine steady, one the fits to the Thermostat housing 30ukp,
New engine mounts, steady bushes
A 1275 top radiator hose and Radiator top mount, both of these should be available from Any mini specialist. 15ukp,
An engine lifter of some description a Hydraulic one
costs about 20ukp for a weekend.
If your mini was made after 1989 it will have a Servo. The metro crank case breather (the one on the clutch side) fouls the servo. You will need the Flame trap that is used on the Early-late Coopers (bends in a funny direction. 15ukp
Once you have the engine there is a decision to be made. All metros have a Diff ratio of 3.44:1 (except the Turbo Metro which has a 3.2:1) 3.44 Diff are cool for around town use excellent acceleration but you will be doing 4,000 rpm at 70mph and 6000rpm at 100mph. 85 on minis have a 3.105:1 Diff that gives 3600rpm at 70mph and 5,000ish at 100mph. I haven't done a Diff swap but have experienced 3.105:1, 3.21:1 and 3.44:1 Diffs If you don't mind doing 5,000ish at 90mph (the speed I usually do on the Motorways) then the 3.44:1 is what you want 4th gear acceleration (70-90mph is unbelievable!!)
You will HAVE to do the following to your new engine,
1) Drill a few small holes in the thermostat, Because Metros don't have bypass hoses you need to restore the through flow of the system when the thermostat is closed. The bypass hose lets water go back into the water
pump from the head this is what the holes the thermostat do but the water goes via the radiator.
2) Fit a mini thermostat housing, The metro uses different size hoses this means that if you use the metro one the top radiator hose will not fit.
3) Transfer all Mini engine mount adapter plates to the new engine. Don't worry compare the engines when you have them out and sitting on the floor you will see what I mean.
4) At least renew the drive shaft seals or even better dismantle and rebuild!! (I didn't and the engine changed its oil every 3 weeks). But if you see the engine in that you are going to buy whilst it is the car check the ground underneath the sump for leaks. If that is ok then don't bother changing them
5) Renew Plugs, Leads, Rotor arm, etc.
6) Renew the oil filter,
7) Fit the Radiator before you put the 1275 in the car as this is a bastard with the engine in.
8) You can use either the mini water pump pulley or the metro one, if the metro one is used the fan and water pump will spin faster.
9) You have to 'adjust' the crank case breather flame trap on the radiator side of the engine with a large hammer to clear the radiator fan.
Doing the Deed!!!
Taking the engine out of the Mini is simple just go as per the Haynes Manual. The same with putting the metro engine in. This really is the easiest bit!!!
Metro parts which can be used on a Mini
Engine, Front disks/caliper/drive flange combination, handbrake grip, instrument pod, master cylinder, horn, radius arms? (if beam axled), clutch parts if non-cable, carb, inlet, radiator & fan (keep hoses) , oil intercooler (MG metro), Rear brakes, brake limiter, bulbs<g>, you could use the seats, the steering wheel, window winders, rear wiper motor if you want to fit a custom rear wiper, washer pumps, indicator/wiper switch assy.
MG metro head, differentiating it from a MG Metro *TURBO* head
The MG metro turbo head has the same valve sizes as the standard mini/metro 1275cc (12g940) head. They all have 1.312" (33.0mm) inlet 1.156" (29.4mm) exhaust valves. The turbo head has Sodium Cooled exhaust valves.
The MG Metro (non-turbo) head has larger 1.410" (35.6mm) inlet valves. This head can also be differentiated from the Turbo head by not having any thermostat bypass hole (the Turbo head has a screw in the hole).
MG Metro head on a 998 block (without mods!)
There has been some talk recently of putting 1275 heads
on to 998 blocks most people say it cannot be done with out a strip down and
modifying the block due to the exhaust valve centers being off. So out came the
blue-tack (cheap plastigauge also used for sticking posters on the wall) I put
the head on the block WITHOUT the head gasket and bolted
it down with the blue tack sitting on the offending sticky out bits on the block. I adjusted the rockers so that they were touching the valves rather than 0.3mm this coupled with the lack of head gasket gave a bit of extra confidence. With all this done I turned the engine over by hand a few times. Then took it all back off again. to find that there was loads of room (about 1mm) on all valves. COOL I thought. There are a couple of things to look out for when you do this mod. The height of the block relative to the water pump is less I had to modify the top of the water pump and use the smaller water pump pulley (as found on metros) also metro cylinder heads don't have a bypass hose so either block the hole in the pump or get a new pump. Other than that all went smoothly. But don't forget that you need a 1275 top radiator bracket. and If you have a UES (ultimate engine steady) you need the 1275 variety. Mine only just fitted due to the tappet chest beather it had to be modified slightly with Bl tool H.A.M.M.E.R.
MG Metro, oil intercooler
It doesn't matter how hot the oil is (within reason),
it's the viscosity that is important. It's fine to heat it up quick, so long as
it doesn't thin out.
The intercooler will basically conduct heat from the hotter fluid to the cooler one.
Water has a greater SHC than water and will require more energy to heat a litre up by a certain temperature. That means the oil will heat up quicker, and will then transfer heat to the water (hence oil 'cooler').
MG Metro Turbo, differences to MG Metro (non-turbo)
- Turbo has lower compression (bigger piston dish volume)
- Different cam (shorter duration?) (2)
- Chunkier gearbox (eg: first motion gear bearing)
- Inlet valves smaller (3)
- Exhaust valves sodium cooled
- Higher geared diff (3.21)
- Higher capacity oil pump
- Turbo oil return into old mech fuel pump aperture
- Verto clutch uses AP Racing un-sprung (old-style) friction plate
(1) Lower CR than the MG metro but the same as a std. 1.3 metro (9.4:1 and 10.5:1
(2) Same as a std 1.3 metro
(3) Same size valves as a std. 1.3 metro
(4) MG Turbo has a 3.21:1 the MG has a 3.44:1
Join the Minilist share your joys and woes with 500+ mini owners worldwide via Minilist at Yahoogroups