clutch for 1275 engined Minor

[smithskids]

What would be the best clutch set up for a 1275 engined minor please. I recently renewed my clutch with a south coast supplied one and noticed it had considerably less surface area than the original one I replaced.

[philthehill]

The best clutch assy for your 1275cc engine depends on several factors.
What 1275cc engine do you have fitted Marina/Ital/Midget?
What flywheel do you have fitted?
Is it a 1098cc flywheel converted to suit the 1275cc crankshaft?
What gearbox do you have fitted?
A photo of the flywheel/clutch assy, the engine number and any additional information available would be of benefit.
The 1275cc Midget clutch is smaller than the 1098cc clutch assy but is stronger as it is a diaphragm clutch whereas the Minor clutch pressure plate is held with coil springs.
The 948cc clutch assy is smaller than the 1098cc clutch assy which is normally fitted when using the 1098cc modified flywheel.

[smithskids]

Hi Phil, it is an MG 1275 unit I built many years ago coupled to a standard 1098 gearbox. I redrilled the1098 flywheel for 6 bolts and I had a 6 red spring clutch cover fitted and it would start to slip at max torque if you floored it at 3500 rpm. as long as you accelerated moderately it was OK. The engine has a 270 kent cam fitted and 36mm rimflow inlets with an HIF 6 SU. It will pull from 20 mph. up to max in top gear. As I said the new clutch plate has less surface area than the old worn B& B plate. I have the MG clutch assy that came with the engine but I remember it was a rather short pedal movement when I had it in the MM. May be the new clutch plate will bed in with use.

[les]

I found the diaphragm type clutch didn't feed in very smoothly, maybe not a worry if you tend to give the car a hard time. For comfortable driving I changed to a spring pressure plate.

[philthehill]

I am intrigued by the less surface area statement!
What clutch centre plate have you fitted?
Do you know the inner and outer diameters of the clutch centre plate?
I suspect that the clutch fitted will not get better even when bedded in.
Unfortunately the clutch is usually the first thing that needs to be upgraded when the engine has been tuned / improved.
To overcome the problems you have it would be better to get a matched uprated clutch cover and centre plate.
When I first uprated my clutch I fitted a re-faced and re-drilled Midget 1275cc flywheel and installed a 7.5" diaphragm clutch pressure plate with uprated centre plate which was used with a 1275cc Midget gearbox: Photos below of clutch and flywheel..
Whilst being a diaphragm cover the clutch was not fierce or either IN or OUT - just normal.
Peter May Engineering MG specialists do several versions of uprated flywheel & clutch. I would suggest that the 7.5" Rally clutch would meet your needs but speak with Peter May Engineering to determine you needs against what they supply.
https://www.petermayengineering.com/cat ... catalogue5

As an aside:
I would be wary of dropping the clutch or flooring the engine at high engine revs when you only have 6 bolts holding the flywheel to the end of the crankshaft.
The 1275cc Midget has 6 bolts, two dowels and a register both on the end of the crankshaft and inside the front of the flywheel.
They hold it all together.
It would be better to revert back to the Midget flywheel and get it re-faced and re-drilled to accept the 7.5" clutch.
Phil

[Chipper]

I would personally go with the standard Midget Borg & Beck diaphragm clutch - I've used one on my 1275cc Midget engine Traveller for years now, with no problems.

[IslipMinor]

We have the standard 1275 crankshaft, flywheel and 6.5" diaphragm clutch cover in our 1380 and never had any issues with slippage. The driven plate is a combination of Midget 1275 facings and Toyota 21T spline centre, but the torque capacity is determined by the cover not the driven plate.

It is certainly not 'digital' in operation and very easy to drive in traffic. At a standstill it can get a little heavy after a while, but then it should have been put into neutral long before that occurs, shouldn't it??

[smithskids]

Thanks folks I have a new radiator due to-day so I may as well whip the engine out and put the diaphram clutch in whilst I am at it and see. Pictures will follow when it is out.

[philthehill]

Are you going to fit the proper 1275cc Midget flywheel before it goes back together?

[smithskids]

Yes Phil, it has 3 clutch cover dowels as against 2 for the 1098 flywheel. I even found the modified clutch control arm I made to get the clutch pedal free travel. I think I will give it a rest till next week as I am going up to a do at the North york moors railway in the MM sidevalve. At 79 it takes me three days to do an engine out and back when I was younger it was a saturday morning job.

[philthehill]

Just in case there has been a misunderstanding as regards dowels - when I referred to the two dowels in my post above I was referring to the two dowels fitted into the rear face of the crankshaft and not the dowels holding the clutch cover in place.
Those two dowels assist in stopping the flywheel rotating around the crankshaft register. The 6 bolts are not fitted but the dowels are.
Phil

[smithskids]

Hi Phil, yes when I redrilled the flywheel I added the extra dowel. I am in the process of stripping an old clutch cover to measure the springs. According to B&B info sheet red springs should be 1 1/2" long and 195 lbs fully loaded. Clutch assy. 975 or 987 model 8A7. Part no. red springs 4446. Yellow springs 140 lbs. at 1 1/2" part no.4331. What I don't know is the distance from the clutch plate to the flywheel face distance. Of the 3 covers I have to look at the distance varies from 3mm to 6mm.

[philthehill]

The 3mm difference between the clutch covers I would consider to be within tolerance.
What is most important is the height of the fingers on which the carbon thrust bearing plate presses. The bearing plate must be removed for measuring as the bearing plate can and does vary in thickness.
Section EE of the Minor workshop manual explains how to set the finger but does it with the special tool Pt No: 18G99 A.
Unfortunately it does not give the specific height of the finger but refers you to the B&B chart which you may have.
If not use one of the other covers to give you a datum for finger height.
Setting the fingers can be done without the special tool by attaching the cover to the flywheel and using solid spacers to replicate the thickness of the clutch centre plate.
Tighten the cover to the flywheel and measure the height of the fingers from the flywheel and they should all be the same.
If not the same height - adjust using the finger adjustment nuts - re-tab the nuts when finished.

[smithskids]

Thanks Phil, I managed to set them by bolting the clutch assy. to my lathe faceplate with spacers in. I was surprised at how little you had to adjust them to achieve equal setting.

[smithskids]

Engine out to-day!

Morris 1275 eng 2.jpg (310.91 KiB) Viewed 3189 times

Morris 1275 eng 5.jpg (223.22 KiB) Viewed 3189 times

Morris 1275 eng 6.jpg (282.24 KiB) Viewed 3189 times

The old center plate was bigger than the new type, also it isn't segmented therefor it had a greater surface area and was slipping. The new type hadn't a chance.

[philthehill]

Many thanks for posting the photos.
I would suggest that your clutch assy is inadequate for the engine power output and it does need to be uprated.
The difference in rubbing/lining area (segmented or not) is going to make little difference.
The controlling factors are the pressure plate loading (spring pressure) and the driven plate diameter.
As I suggested in my post above you do need to upgrade the clutch and use either a standard but preferably uprated 1275cc Midget clutch assy or a 7.5" rally clutch from Peter May Engineering or similar.
Unless you uprate the clutch you will continue to have problems transmitting the power through the clutch.
Having been there, got the video and the tea shirt I can speak from experience.
This was the first 7.5" uprated clutch I fitted to accommodate the increase in power from my 1275cc engine and it was only just adequate then.

An observation:-
I would suggest that your flywheel was originally from a 948cc engine. You state that the flywheel is not a 1275cc Midget one but a 1098cc flywheel which I believe to be incorrect. The inner ring of bolt holes and locating peg holes correspond with those of a 948cc flywheel or possibly even a refaced 1275cc flywheel. Unfortunately only a view of the flywheel to crankshaft face will confirm the origins of the flywheel.
Whilst it should make no difference - the flywheel does need to be correctly identified.

Phil

[IslipMinor]

My experience with a highly modified 1380 engine (Midget 1275 block), with 112 bhp and 108 lbf. ft. torque, is that the standard 6.5" diaphragm cover copes very well over a long period of time. We do have a different driven plate to suit the Toyota gearbox, but the cover plate is 100% standard 1275 Midget. The uprated one from AP has not been available for many years, unfortunately.

The flywheel is standard 1275, apart from lightening and balancing, and over 19 years and almost 60,000 miles we have replaced the driven plate once (only as a precaution as the engine was out) and the cover plate twice. The first time was when I fitted a roller release bearing that required the cover plate pressure plate to be removed, and again when I removed the roller release and went back to a standard carbon thrust release bearing.

The car is driven enthusiastically when the opportunity arises, plus 2-3 track days per year and still does not slip! There is one exception, but the occasion is so rare that it does not matter - a full throttle slipped clutch start from a standstill. It's not a practice that I use, as it is quick enough away from a standstill with a more gentle take-off.

[smithskids]

New old stock B&B clutch cover assy with red springs (46082/22) fitted with plate 47624/84 fitted last week and problem gone!! Should be good for the Humber Bridge Drive in on Friday evening