1275 onto 803 gearbox

[roymck]

Due to the 948 engine unexpectedly expiring I need to fit a replacement engine a bit sharpish . I know its not advised as yes the gearbox wont last long, but I need to fit a spare 1275 Sprite engine onto the 803 box as a temp fix .
Has anybody done it, I know the 1098cc clutch has clearance problems inside the bellhousing but the 1275 cc clutch is smaller.
Anybody got any constructive comments.

Thanks Roy

[IslipMinor]

Roy,

Apart from the obvious comment to be very gentle with it, the release arm pivot point in the front cover is further forward in an 803/948 gearbox than the 1098/1275, so I would check the clutch action to make sure that the carbon thrust bearing does not rub on the primary shaft splines at any point during the clutch action. Also I think there are different width thrust bearings, which could also affect the way it works with an early box and 1275 clutch.

[bmcecosse]

Use the 803 flywheel and clutch for simpliicty.

[mike.perry]

The 1275 has a diaphram clutch which will give a short, heavy pedal action, OK for motorways and racing circuits but no good for the daily commute. The arm on the relay shaft which connects to the pedal linkage needs to be extended by an inch and the hole re drilled. This will restore normal clutch feel and movement

[roymck]

Doesn't the 1275 flywheel have different fixings 6 bolts instead of 4 as used on the 803 948 and 1098 ..

[bmcecosse]

Indeed - so just use the 4 you need....Simples !

[philthehill]

Yes the 1275cc engine/flywheel attachment is different! The 948/1098cc Minor uses just the 4 bolts against the 6 bolts and two studs of the 1275cc engine.
ESM do a flywheel conversion to allow the 1275cc engine to be fitted to a Minor gearbox. Part No 10M001 @ £48.50 & exchange.
Not sure that you can just use four bolt holes of the six (plus 2 stud holes) but happy to be corrected. I have just put a divider between the 6 holes of a 1275cc flywheel and although they may look equidistant they are not so 4 into 6 will not go.
You may have to play around with the carbon thrust i.e. file a grove in the upper part of the carbon to clear the first motion shaft when the clutch pedal is depressed and the carbon thrust moves forward; that was how I overcame the problem of the relationship between the clutch carbon thrust and first motion shaft when I fitted a 1275cc to a Minor gearbox and it worked well for me.

[bmcecosse]

I think I only had to drill two extra holes to use 1098 fly on 1275 crank......

[philthehill]

Bmc
You do not state whether you drilled and tapped two extra holes in the 1098cc flywheel or 1275cc crank flywheel flange!
If you drilled the holes in the flywheel why did you need to tap the holes? Drilling the crank and tapping the holes is no easy job and there is little spare metal on the flywheel attachment flange to drill an extra two holes. Personally I would not attempt drilling and tapping the crankshaft flywheel flange but go for the modified flywheel as supplied by ESM or carefully drill the required extra holes in the flywheel as there is more metal to play with. When I did my conversion I obtained a modified flywheel from MOSS which made the job so much easier.

[bmcecosse]

Ahh -sorry - slip up - just had to drill holes in fly. Nothing done to crank. It was a long time ago........

[roymck]

Whats wrong with keeping the 1275 flywheel , it fits the engine . Is it the clutch that's the problem?

[bmcecosse]

It may be - but give it a try! Possible problem with starter too.... As others have advised - it will be v heavy, but if this is a short term solution (till the gearbox breaks....... ) then perhaps you can live with it.

[IslipMinor]

Is the 'heavy' 1275 clutch a real problem? We have a 1275 pressure plate and standard Minor rod linkage and while it is not as feather light as a typical 'modern', we use the car in all conditions, including crawling in traffic queues and never noticed that it is particularly heavy.

I would suggest to try it as standard, as it can easily be modified afterwards if required.