1275 Engine comparisons

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Martlin
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1275 Engine comparisons

Postby Martlin » Thu Nov 07, 2019 9:21 pm

Hi,
A couple of questions,
What are the main differences between an Ital 1275 A+ and a 1275 MG Midget engine?
Will a 1275 Midget rear axle assy. fit a Minor 1000?
Many thanks in anticipation.
Martin.

philthehill
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Re: 1275 Engine comparisons

Postby philthehill » Thu Nov 07, 2019 10:50 pm

There are very little differences between the 1275cc Marina/Ital engine and the 1275cc Midget engine as regards performance.
The most obvious difference between the two is the location of the oil filter.
The crankshafts are different in that the Marina/Ital big end journal are larger to compensate for using a lesser grade materials in its manufacture.
The 1275cc 'A' Plus engine block has strengthening ribs added.
The conrods are different.
The rear engine plates are different.
The front engine plates are different.
The timing chain arrangements are different.
The distributers and means of securing it are different.
The distributer drive shafts are different
The flywheel is different in that the Marina/Ital is secured with 6 bolts and one dowel. The Midget flywheel is secured by 6 bolts and two dowels and a register.
The timing chain covers are different.
The flange at the bottom of the block and to which the sump is secured to can be thick or thin on the 1275cc Midget block. The 1275cc Marina/Ital flange is the same thickness.
The sumps are different but can be exchanged.
Some 1275cc Midget blocks have a hole in the support web of the centre main. Very few Marina/Ital 1275cc blocks have the hole.

The cylinder heads are the same.
The camshafts are the same.
The oil pumps are the same.
The water pumps are the same.
The crankshaft pulleys are basically the same.
The oil pick ups are the same.

The Midget rear axle is too narrow to fit on the Minor springs. The diff will fit.


Martlin
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Re: 1275 Engine comparisons

Postby Martlin » Thu Nov 07, 2019 10:55 pm

One post has answered allied my questions comprehesively,many thanks Phil!
Martin.

jagnut66
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Re: 1275 Engine comparisons

Postby jagnut66 » Fri Nov 08, 2019 12:10 pm

Additional to the above, the one advantage a Midget engine has is that it is a straight swap / fit, without the need for any modifications, if your car already features an 'A' series engine.
I believe with the Marina / Ital engines you will need to modify the engine mounts.
The Midget gearbox will go straight in as well.
I'm not sure about the Marina / Ital gearboxes.
However the 1275 engine is slightly longer, so an electric fan is a good move, as the metal fan can foul the radiator.
Best wishes,
Mike.
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les
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Re: 1275 Engine comparisons

Postby les » Fri Nov 08, 2019 12:18 pm

Probably the front engine plate that Phil mentioned takes care of the engine mount situation.


philthehill
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Re: 1275 Engine comparisons

Postby philthehill » Fri Nov 08, 2019 12:38 pm

Fitting the Minor front engine plate to the 1275cc Marina/Ital engine takes care of the engine mounts.
The Marina/Ital engine mount holes in the block can be either right through or blind. If right through the holes can be blanked by using the Marina/Ital mount bolts.

The front of the 1275cc engine block is in exactly the same place as the front of the 948cc/1098cc engine block. The block does not move forward when fitted to a Minor using the Minor front engine plate. There is plenty of room at the rear of the 1275cc block/Head when fitted to a Minor. The heater tap may have to be turned slightly to clear the battery tray.

The 1275cc Midget engine has a plastic multi blade fan which should be replaced by the Minor twin or four bladed fan if using the Minor radiator.

The Marina/Ital gearbox will not fit the Minor without modifications to the body work and will not mate with the standard Midget 1275cc engine.


jagnut66
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Re: 1275 Engine comparisons

Postby jagnut66 » Fri Nov 08, 2019 3:48 pm

when fitted to a Minor using the Minor front engine plate
Needless to say when I fitted the Midget engine into Abby I fitted it 'as is' and didn't change the front plate for the Minor one.
I didn't need to alter anything regarding the mounts but I did find the metal fan fouled the Rad.
Best wishes,
Mike.

NB: I can recommend the Revotec kit to anyone who needs an electric cooling fan, it is very good but not cheap.


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Martlin
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Re: 1275 Engine comparisons

Postby Martlin » Fri Nov 08, 2019 5:56 pm

Many thanks for all replies.
Fitting the Ital engine I had to use a Minor front plate and an ESM modified backplate and flywheel,I used the original Minor 1098 gearbox and fitted a needle roller bearing in the end of the crankshaft.
Being a cheapskate I modified the fan blade by cutting it to clear the breather as highlighted in a previous post.An exact amount has to be removed from each end,this is where a vernier caliper is very useful. So far no problems with the temperature.Simples! :D
Thanks again all,
Martin.

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Re: 1275 Engine comparisons

Postby SteveClem » Fri Nov 08, 2019 6:32 pm

Way beyond my technical expertise, but from a driver’s point of view the Marina 1275 with a Ford type 9 gearbox results in a very capable and enjoyable car. :D

jagnut66
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Re: 1275 Engine comparisons

Postby jagnut66 » Fri Nov 08, 2019 8:58 pm

I didn't get on with the two type 9's I fitted, both proved probematic, despite being rebuilt.
In the end I reverted back to a Minor rib case gearbox and never had any more problems.............
The only thing I would say is that if you drive it spiritedly you may find it worth your while to source a stronger Midget box.

As a side issue, can anyone explain why the later larger (1275 and 1500) engined Midgets never had 'overdrive' as a factory fitted option (or even as standard)?
Best wishes,
Mike.
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philthehill
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Re: 1275 Engine comparisons

Postby philthehill » Fri Nov 08, 2019 9:51 pm

Basically the Midget/Sprite transmission tunnel was not designed for an additional overdrive unit. It was a tight fit for the standard gearbox let alone the additional length/size of the overdrive unit.
By the time Triumph joined the B.L fold the Midget/Sprite were on their way out and BL were not going to heavily invest in major new body pressings just to accommodate any additional overdrive unit.
Any modifications to the transmission tunnel to accommodate the alloy Triumph bell housing and 1500 engine would be minor compared to remodelling the whole transmission tunnel and cockpit floors. Those minor amendments could be incorporated during the body build.
The Spitfire which had the overdrive option had a removal fiberboard transmission tunnel which could be easily re-moulded to accommodate the overdrive unit. The Midget/Sprite transmission tunnel formed part of the monocoque and could not be so easily re-formed. With the Spitfire the gearbox and overdrive unit sat above the separate twin rail chassis spine giving more variables to the transmission. The differential was fixed to the separate chassis so there was no length variables to the power drive between overdrive and final drive. The Spitfire rear suspension was by transverse leaf spring and transverse swinging arms formed at the top by the spring and below by the exposed drive shaft.


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Re: 1275 Engine comparisons

Postby midget » Sat Nov 09, 2019 10:43 am

I have just started to build an A+ block with 1275 Midget crank,rods etc in order to seamlessly fit to a late Midget needle roller bearing box.
Parts are currently at Machine shop, and just to be clear, are all the 1275 pistons the same deck height?
I don't yet know if they are reboring the block, so need this info for rebuild. I have been told that gudgeon pin sizes are common to both.
John

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Re: 1275 Engine comparisons

Postby philthehill » Sat Nov 09, 2019 12:40 pm

The piston top height above the gudgen pin is the same for all 1275cc engines/pistons.

The gudgen pins are the same outside diameter (0.8123" - 0.8125") for all 1275cc engine. They are selectively fitted to the piston and should not be swapped around between pistons.

The gudgen pins fitted to the 1275cc engines are a very tight press fit through the con rod small end which requires special tools, 18G537, 18G1150 & 18G1150A for fitting (and removing) the piston/gudgen pin to and from the con rod.
Some heat up the small end to expand the small end hole to allow the rod to be slid through. The problem is that the rod soon cools and the gudgen pin can be trapped off centre and then it is difficult to rectify. Better to get the machine shop to fit the pistons to the rods.
Heating the small end to the required temperature can effect the molecular structure of the rod and should be avoided at all costs.


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Re: 1275 Engine comparisons

Postby midget » Sat Nov 09, 2019 3:03 pm

Thanks for clarification Phil. I will of course leave the fitting of the pistons to rods to the machine shop.
John


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