Cluth Release or Throwout Bearing

Post by **DonMiller** » Thu Feb 12, 2009 7:07 pm

Hello Morris Minor Wizards. I am almost ready to install my newly overhauled 1250 in place of the old 948cc motor. I noticed the original throwour bearing had the mounting pins in line with the bearing but the new bearing is offset by about 3/4 inch. Question is: "which is the correct bearing?"

Mini Mania told me the only way to find out is to put the motor in. I say there is someone (here?) whoa actually knows the correct answer...
I've enclosed a photo that compares the two.
Thanks
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Post by **PSL184** » Thu Feb 12, 2009 7:12 pm

Depends what gearbox / clutch assy you are using...?

Post by **Mogwai** » Thu Feb 12, 2009 7:41 pm

I think the deeper one may be for the midget/sprite diaphragm clutch

Post by **DonMiller** » Thu Feb 12, 2009 8:31 pm

Didn't change the gearbox - just pulled the 948 and the clutch on the 1250 looks about the same. Is there a measurement (distance between the pressure plate to the clutch shroud, for example)? My inclination is to reinstall with the old clutch release bearing but am trying to avoid putting the motor in and out twice (or more!)

Post by **PSL184** » Thu Feb 12, 2009 8:46 pm

The 1250 (sic) (1275) clutch is bigger than the 948. If you are keeping the 948 box then you need to use the 948 clutch. Obviously you need the backplate off the 948 also which needs to be machined to clear the oil pump and crank rear main on the 1275 block. Better still, use the ribbed case box from a 1098 - You still need the mods but the box is stronger and the 1098 clutch can then be used.

Post by **mike.perry** » Thu Feb 12, 2009 10:17 pm

The lower thrust bearing fits Series MM/803/948. The upper thrust bearing fits 1098 and depending on what box/clutch you are using it also fits the 1275.
You don't say which 1275 engine you are fitting, Midget or Marina/Ital?
If you are fitting a Midget engine I believe that you will need to change the back plate to take a 948 g/box. The 948 box is not as strong as the 1098 or 1275 boxes so I would not advise using it with the 1275 engine. I cannot comment on the Marina engine/box as I have never fitted one. However once we have established which engine you are fitting then I may be able to offer further advice

Post by **bmcecosse** » Thu Feb 12, 2009 10:34 pm

Why do you say '1250' - is it a specially bored 1098 engine , or just a normal 1275 engine ? If you keep the 948 gearbox - don't expect it to last very long. Generally - you need to keep the flywheel and backplate and clutch etc from the 948 if using a 948 box. And you will find that a 1275 crank has 6 flywheel bolt holes - and a 948 flywheel only has 4 bolts, 2 of which will line up with a pair on the 1275 crank. You need to drill the other 4 holes accurately through the old flywheel. DO NOT be tempted to fix the flywheel with only 2 bolts !!!!!
It 'may' just be possible to use a 1275 Spridget flywheel and clutch with a 948 box - I'm sure someone will confirm or deny that shortly!
I haven't got a carbon thrust handy - but I don't remember seeing all that offset on a Minor thrust ? Surely the lower thrust is the correct one ?

Post by **PSL184** » Thu Feb 12, 2009 11:14 pm

Yes, the Spridget 1275 uses the same size flywheel as the 948/1098 but apparently if you go down this route the clutch is extremely heavy. Can't remember why but I think Carlo had tried it and told me about it...?

Post by **Kevin** » Fri Feb 13, 2009 12:05 am

PSL184 wrote:Yes, the Spridget 1275 uses the same size flywheel as the 948/1098 but apparently if you go down this route the clutch is extremely heavy. Can't remember why but I think Carlo had tried it and told me about it...?

The 948 Spridget and Minor have the same size clutch 6 1/4"
The 1098 Spridget and Minor also have the same size but its 7 1/4"
But the 1275cc Spridget uses a 6 1/2" clutch and when this engine/flywheel combination is used with the 1098cc gearbox it gives a heavy action in a sort of on or off action that is not very nice that's why its best to use an adapted 1098 flywheel.

Post by **bmcecosse** » Fri Feb 13, 2009 12:06 am

The 948 and 1098 flywheels are different!

Post by **PSL184** » Fri Feb 13, 2009 7:54 am

Thanks Kevin, makes sense now ;-)

Post by **IslipMinor** » Fri Feb 13, 2009 7:58 am

From my experience (11 years and 30,000+ miles) the A-Series 1275 diaphragm clutch is very easy, not heavy and very progressive, just as it is in a standard Sprite/Midget application. I am using the standard Minor mechanical linkage and carbon thrust bearing.

Is it the Marina/Ital clutch that is heavy? What size is that?

I have retained the bulkhead steady, but no retaining wire on the gearbox, as there is no facility on a Toyota box!

Don,

With a 1275 engine, assuming it's a Midget variety, I would not use the 948 at all, it's much too weak. The same applies to the 948 clutch, it will not take the torque from a 1275 engine. Stick with the standard 1275 flywheel and clutch and fit either a 1098 or 1275 Spridget gearbox. The 1275 is actually stronger, and has closer ratios - also quite difficult to find though. For a standard (ish) 1275 a good 1098 box should be ok.

If it's a Marina/Ital, then there is quite bit of modification to fit an A-Series gearbox, or a different amount of modification to fit the Marina/Ital gearbox to fit it into the car itself.

Can you give some more details of the engine you have?

Where did the deeper thrust bearing come from? What is it intended to be for?

Post by **bmcecosse** » Fri Feb 13, 2009 10:54 am

mp says it is for 1098/1275 use !

Post by **jaekl** » Fri Feb 13, 2009 12:54 pm

I thought the standing advice is to use all of the clutch parts for that particular engine regardless of gearbox. The only difficult combination is 1098 and a smooth case.

Post by **PSL184** » Fri Feb 13, 2009 12:57 pm

jaekl wrote:I thought the standing advice is to use all of the clutch parts for that particular engine regardless of gearbox. The only difficult combination is 1098 and a smooth case.

That won't work cause you can't get a 1275 flywheel to fit in a Minor gearbox

Post by **IslipMinor** » Fri Feb 13, 2009 5:10 pm

That won't work cause you can't get a 1275 flywheel to fit in a Minor gearbox

The 1275 A-Series flywheel is the same basic size as the 948/1098 engines and the gearbox bellhousing is also the same size, irrespective of engine.

Are you thinking of the Marina/Ital 1275 engine?

Post by **mike.perry** » Fri Feb 13, 2009 5:15 pm

The 1098 and 1275 gearboxes are interchangable, the only external difference is the reversing light switch on the 1275 box.
The simplest set up is to use the diaphram clutch on the Midget engine and weld one inch onto the relay shaft lever that connects to the clutch pedal, and re drill the hole. This will have the effect of increasing the leverage and decreasing the load. Without this modification the clutch will be very sharp and heavy and you will not enjoy driving in traffic. You will need to use the 1098 thrust bearing. A further refinement is to use a Birmingham MMC (advertising again!) ball bearing thrust bearing. You will then only have to adjust for wear in the clutch plate and not in the thrust bearing

Post by **PSL184** » Fri Feb 13, 2009 5:22 pm

IslipMinor wrote:
That won't work cause you can't get a 1275 flywheel to fit in a Minor gearbox
The 1275 A-Series flywheel is the same basic size as the 948/1098 engines and the gearbox bellhousing is also the same size, irrespective of engine.

Are you thinking of the Marina/Ital 1275 engine?

Yes, that is the engine I was referring to.... We still don't know what engine is trying to be fitted here and the 948 box prob isn't strong enough ?

Post by **mike.perry** » Fri Feb 13, 2009 7:54 pm

I do wish people would give exact specifications when asking questions. It would save an awful lot of time and effort. We have had no comeback to the question of what engine.

Post by **bmcecosse** » Fri Feb 13, 2009 9:08 pm

Original poster has not come back - we all bash our gums to no effect! The reality is that most NS 1275 engines are ex Marina/Ital - not so many Spridget engines about (except in Spridgets of course!) - and the Marina/Ital flywheel is larger and won't fit in a Minor gearbox bellhousing. We don't even know for sure if it IS a 1275 engine ! The post mentions a 1250 engine - which is an overbore on a 1098!