17 replies to this topic

[Pullstarter]

Hi guys,

I have an MG Metro motor (I think) in my Mini, engine prefix 12HD24. Does anyone know if the diff in these units is a shorter ratio due to being designed for the Metro (I would imagine it had maybe 13" wheels standard)? Mine seems to rev very high at 60mph (not sure exactly as no tach) and it's a bit annoying trying to drive anywhere with a speed limit above 50  

 

Any help much appreciated.

 

Cheers

Simon

[skoughi]

Think they're all 3.44-1, somebody with more knowledge may correct me! Have you done a google search on the subject? I do have an MG Metro gearbox in my garage but I'm not going out just now to count teeth for you!!

[nicklouse]

the used a mix of diffs the same the Mini but that has the 3.44 a useful page for you

http://www.guess-wor...Tech/engine.htm

[Pullstarter]

Thanks guys! Much appreciated 

[Spider]

According to all the factory Manuals, the MG Metro had a 3.44:1 FD Ratio from start to finish of production.  The MG Turbo had a 3.21:1 FD also from start to finish, however, in later years, it seems to have received one of the 'Economy' drop gears.

[Pullstarter]

It does seem to rev it's 'arris off at anything over 90kph  Maybe be better of with a 3.2? 

Edited by Pullstarter, 17 November 2018 - 02:29 AM.

[nicklouse]

It does seem to rev it's 'arris off at anything over 90kph  Maybe be better of with a 3.2? 

define revs its arris off 

 

should only be doing about 3.5K at 90 Kmh in 4th.

[Spider]

I was about to post more or less the same reply as Nick.

 

Respectfully - while it may to your ears 'sound' like it's 'Reving its arris off' - it could well be getting in to it's sweat spot.

 

A lot of the time, the 'Reving' sound many hear is in fact the cooling fan.

 

Put a GPS and a Tacho in it (even if a bodge temp job on the Tacho) and let's see what is really going on, not what you think your ears are saying  

 

These Engines don't mind cruising in the range of 3500 to 4200 all day. Might appear 'high' when compared to modern engines, but they are happy cruising there. 

[Pullstarter]

I definitely need to try the GPS, will see what I can do about the Tach. Thanks guys. 

[absx2]

Back in the days when you could buy a good running MG Metro for 50 pounds quite a few of their engines ended up in my minis.

It seemed every time regardless of speedo type the speed would read progressively 8 mph out so 22 mph was 30, 30 was 40, 38 was 50, 46 was 60, 54 was 70 and so on.

At first although the engine seemed lively it wouldn`t go much over 80 mph :)

 

So i`m wondering if your speedo is calibrated ? 

[Cooperman]

The 3.44:1 was the ratio for the original 1275 Cooper 'S' and is an ideal compromise for both acceleration and cruising.

 

The A-series will be happy cruising at 4000 rpm which, with a 3.44:1 is about 78 mph in 4th. 

 

These are old type cars and and cars were lower geared back then. The fun is the retro-type driving experience.

 

Best advice it to get a tacho fitted. With old Minis a tacho, oil pressure gauge and voltmeter are always a good idea.

[Pigeonto]

I'm with Moke Spider on the fan noise. 

My engine driven fan is removed in the winter as I have a manual/automatic electric one + other extra cooling and honestly, the difference if huge

[Pullstarter]

Thanks guys, all good advice. Will definitely get a tacho sorted as soon as I can. 

[Pullstarter]

Finally got a tacho installed and took the car for a run with a GPS speedo on the phone (my car speedo is woefully inaccurate). So I'm doing 3000rpm at 50mph (80kph) and approx 3900rpm at 60mph (96kph). From these results and what you guys have said I'm guessing the fan is the thing that's making all the noise?

 

Thanks for all your help guys I really appreciate it. 

 

Cheers

Simon

[timmy850]

All of it will be making noise - fan, exhaust, intake etc. Have you got any insulation under the bonnet or on the bulkhead?

 

My car uses a 3.76 ratio, so at 100kph it's over 4000rpm. It's happy to be above 4000rpm for hours

Edited by timmy850, 21 November 2018 - 03:49 AM.