1275cc replacing a 1098cc

[Captain flint]

Hi all,
First many thanks to all you guys who have given me good advice in the past.
After many months of searching out of the blue I have dropped on an MG Midget
1275cc engine! Great joy!
My query is this, I have a five speed Ford gearbox conversion mated to my 1098cc engine,
Will the 1275cc engine mate with the five speed box without any further modification?
Many thanks all.
Martin.

[bmcecosse]

With the exception of the flywheel mods (see many other threads on the subject) to take the clutch from the 1098 - yes, it will.

[Captain flint]

Thanks BMC,
What if I used the 1275cc flywheel and clutch?

[The vast minority]

Lots of reasons not to, although some have.

It's a diaphragm clutch designed to be hydraulically operated which supplied a much shorter stroke at the release bearing for the same clutch pedal stroke.

Thus, if one uses this clutch as a mechanical one it becomes something of an on off switch with very limited biting point range.

It's also going to be much stiffer than the minor clutch that's there now. This can be overcome by welding an extension onto the clutch relay arm but why bother?

By far the best option would be a modified flywheel, unless you have very robust clutch leg.

If you go the midget clutch route i can supply an excellent midget flywheel and clutch if needed.

Al

[philthehill]

Two things spring to mind that will require attention and they are:

1. The bearing in the back of the crankshaft that carries the front end of the Ford first motion shaft.

2. You will have to fit the correct size and with the correct number of splines Ford clutch plate as the MG clutch is a smaller dia to the 1098cc clutch plate.

You could get the MG Midget flywheel faced off and indexed drilled to accept the larger clutch which you already have and which is the way I would go and have been (picture attached).
The 1098cc flywheel will not fit the MG Midget crankshaft.
Phil[frame][/frame]

[The vast minority]

I concur
The flywheel can be modified midget or marina but if you use a marina you need to remove the off centre dowel from the midget crank.

[philthehill]

The Marina flywheel will not go inside a 'A' Series to Ford gearbox adapter bell housing as the Marina flywheel is 300mm overall diameter including starter ring.
The flywheel register on the back of a Midget crankshaft is totally different to that of the Marina and the Midget crankshaft has two dowels for extra rotational security not the one.
Attached is a photo of the rear of a Midget crankshaft modified to accept a Ford first motion shaft - it also has a needle roller bearing and not the usual plain bush.
Note the two dowels fitted.
Phil[frame][/frame]

[bmcecosse]

The Marina fly is indeed a no-no. But I don't see why the 1098 flywheel can't be used - sure it will only have 4 bolts, or you can have it modified to take all 6 bolts - but it will already be carrying the clutch you need and the centre plate stays with the gearbox. It's either that - or as mentioned above - modify the 1275 fly (if it came with the engine?) to take the clutch you have been using on the 1098. Is the crank spigot bearing any different for the Ford gearbox?

[The vast minority]

Ah, sorry then. I was still in the midget-minor mode having just done the 1098 to 1275 swap but kept the minor box.

I'll duck out here in shame
Al

[Mark Wilson]

I think I've changed my mind every time I've read advice on this subject. I'm putting a Midget 1275 engine and gearbox in my traveller, was originally going to go hydraulic, then decided to follow the modified relay lever route. Now the modified flywheel and 1098 clutch sounds better for a daily driver! How much needs to be taken off the midget flywheel? I don't think it makes any difference, but it's the early smaller bearing EN40 crankshaft.

[bmcecosse]

If you have the Midget 1275 flywheel - then USE IT. The little modification to the clutch operating link seems easy enough to do - much easier than messing about with hydraulics.

[Mark Wilson]

I do have the 1275 flywheel, but no clutch at present. The relay lever modification isn't a problem, it was the comment about the limited bite range which worried me, as I want my wife to be comfortable driving it. (She can have quite a fierce bite too....)

[bmcecosse]

The 'limited bite' I believe is when you don't have the lever extension modification - which as I read it, makes it more normal. But I've never done it - so I'm sure others will come on to advise better.

[philthehill]

As regards facing off the flywheel - only enough sufficient to get a totally flat surface right across the clutch face of the flywheel is required.
You will have to then get the flywheel indexed drilled for the securing bolts and locating dowels.
I would recommend that you use a Ford 7.5" clutch pressure plate as the clutch cover is not so deep.
It will still be a matter of trial and error and the clearances inside the bell housing are tight.
Below are photos of the Ford clutch cover I used with the flywheel pictured above:[frame][/frame][frame][/frame]

It is no good me giving you a part number as the clutch cover pictured is an uprated RS 2000 one.

You mention that your crankshaft journals could be different because it is made of EN40.

All of the 1275cc Midget/crankshafts have the same dia main journals at 2.00" nominal and big end journals at 1.625" nominal irrespective of the material they are made from.

The 1275cc Midget/Sprite crankshaft has smaller big end journals than the 1275cc Marina/Ital which has 1.75" nominal big ends because the 1275cc Midget/Sprite crankshaft is made of much better material.

I think that you may be confusing the Marina/Ital and the Midget/Sprite crankshafts although they are interchangeable but only when using the respective con rods.
Phil

[Captain flint]

O.K all,you must forgive me!
I should have realised that the Midget has an hydraulic clutch,and the Minor a mechanical one,DOH!
Right so I am going with the 1098 clutch.
The five speed Ford box and the 1098 engine are in the Morris and being used on a regular basis.
But luckily I have a spare Midget flywheel also a spare 1098 flywheel.
And of course they look very different,the Midget has a register which fits around the crank coupling.
It also has six fixing holes and two dowel locating holes.
The Minor has no register and only four fixing holes with no dowel locating holes.
Now my question is,
Can this be modified by adding two more fixing holes and two dowel locating holes.
Although I have not yet removed the five speed box,I assume (never assume!) that the clutch is already
suited to the Ford box.
Thanks to all,
Martin.

[bmcecosse]

You 'can' - but the correct 1275 flywheel is a MUCH BETTER job - and since you have one anyway I suggest it should be used !