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MG Midget and Sprite Technical - 1275 into 1500 midget

Hi all does the 1275 engine retro fit, with gearbox straight back into a rubber bumper 1500?
J E Fisk

I think you will need to change the prop shaft, gearbox support bracket & mounts and engine support bracket & mount [and possibly more].
Doug Plumb

Ok thanks
J E Fisk

AFAIK it is a lot easier than fitting a 1500 into a 1275 shell.

Apart from what Doug has mentioned, I think you'll find there are no access holes for gearbox oil level/filler plug and for bleeding the clutch.
Dave O'Neill 2

Exhaust will at the least need modifying and carb control cables and some rad plumbing will need changing
Guy W


Got to ask, why would you want to anyway?

The 1500 is more powerful and far torquier in standard tune and hasa far nice all synchro gearbox than the 1275.
SR Smith 1

" -- The 1500 is more powerful and far torquier in standard tune -- "

How true is that?

Why haven't we all been rushing to put 1500s into 1275 shells, esp' given the better Triumph g/box?
Lawrence Slater

Its true, more power, more torque. Just not quite as free revving unless you start with modifications. But I am less inclined to agree with the comment on the gearbox. Yes it has a synchro first but so what! The change is nothing like as nice as a good condition ribcase.
Guy W

Plus the advantages and options of a 1275 mounting up to a 5 speed
Prop and the Blackhole Midget

I think that it would be more complicated than it looks. Engine and transmission mounts are different as is the final drive ratio. The 1275 is a more rugged and tuneable unit but the short clutch life and weak ribcase transmission probably don't justify the modification.

I have a 1275 but restored a 1500 that belongs to my neighbor. Her 1500 is a strong running car (albeit with low oil pressure...)
Glenn Mallory

The final drive ratio *may* be different.

1275s had a 4.2 diff up to '68, then it changed to 3.9

1500s started off with 3.9 and changed to 3.7 in '77.

Having said that, I've just removed a 4.2 diff from a late 1500 axle - bummer!

Short clutch life? Why?

The ribcase gearbox isn't particularly weak, as long as the oil is changed occasionally and you don't keep trying to put it into first when it's moving.
Dave O'Neill 2

I drove the 1275 for 200,000 miles with the ribcase and finally changed it for a Datsun 5 Speed. I found the carbon release bearing short lived and even if the bearing didn't go first, by 25,000 miles, the pedal was all the way to the floor.

I actually got fairly good life out of the ribcases. The first one lasted 95,000 miles. I was able to pick up a new one in the UK in 1977 (there were two left in the BL system and I should have nabbed them both) and drove it for another 95,000 or so before rebuild.
Glenn Mallory


Why does everyone slate the 1500 power train? The oil pressure thing is a myth. Tho it's not quite as free revving as the 1275 due to it's longish stroke, But the torque is far superior. The 1500 has a heavier curb weight than the A series cars, but the performance figures are better however you measure it, explain that?

Mine goes up to 100psi from cold and runs at 75psi, 23psi at tickover.A decent thermostatically controlled oil cooler is a good idea though.

The osly weakness in the crank thrust washers, you ride the clutch at your peril!

Having driven and owned both, I'd says the 1500 box is a nice to use as the A-series, plus it's an easy task to fit overdrive, and seems less aggro than a sieera 5 speed conversion.
SR Smith 1

So I'll ask again.

If the 1500 is so superior, why haven't we all rushed to convert to it from a 1275, and why do so many people convert FROM a 1500, TO a 1275?
Lawrence Slater

For the same reason everyone hasn't ditched their 1275 and bought a modern car as a replacement. Its not all about power, comfort and performance is it?
Guy W

I agree Guy. But we have made mod's where there is a distinct improvement, when they become available. Perhaps a little subjective, but, single hiff, 5 speed, frontline tele dampers, KN air filters, 3 branch, mgf seats, bla bla.

If BMC had altered the front suspension on the midget to the same as the spit, I reckon a lot of people would have converted from the screwed fulcrum, to the spit version.

But very few people rave about the 1500 engine. It may be better than the 1275, but it can't be by much. I don't recall anyone praising it to the extent that the A-series had drawn praise over the years, or been written about as much (vizard as one example).

The title is "1275 into 1500 midget"

Why do it? Because the 1275 has better longevity, it's tougher, and maybe it's just 'purer' to have a Austin derived power unit in a Spridget, than a Triumph. lol.

Who cares though. It's your car, put anything you like in it. I've got a Ford gearbox in mine, and I'm not alone in sleeping with the enemy, in that respect ;).
Lawrence Slater

I have owned both, and could well have written pretty well exactly what SRS said about the 1500. It is more powerful and more torquey, but not to such a great extent that it would warrant swapping a 1500 into a 1275. One can probably more easily get the extra power from an existing 1275 by some fairly simple upgrades as you and I have done. Alternatively, if aiming for an engine swap, then you are straying so far from originality that you may as well go for a K.
Guy W

I thought the Triumph unit is taller and to get it under the bonnet you have to mount it lower in the car.

Therefore to get the same ground clearance with the car if you live in rural areas or built up areas with sleeping policemen you would have to increase the ride height of the care compared to keeping it waith an "A" series!
Eddie Cairns

Ah, is that why the ride height was incresed? I thought it was just US regulations.
Lawrence Slater

Having driven both 1500 and 1275, I would say that the 1500 goes MUCH better.

But a Triumph engine in an MG still grates..........
dominic clancy

It fits ok - and if that's what you want to do - then go for it :)

However, equally, the comments which have been made above are that the 1500 is a good wee engine - much maligned, if only coz it's a triumph ;)

It all depends on what you want really - if you want a high revving engine, then yes, it costs a bit more money to get that out of a 1500 and, even then, you won't get the same result as a 1275, however, high revs aren't the only way to make power.

I don't know the reason for your question (it may just be that your engine is broken and you've got a 1275 lying around :) ) If, however, it's because you want more power, then look towards the triumph guys who have pushed it further than is appreciated elsewhere - even to high revs (there's a guy who autotests a 1500 spitfire that redlines somewhere about 7500 for example!)

Hi Rach, long time no see in these parts!

I like my 1500, but I am biased and never driven a 1275! :-)

I think the ride height/engine height thing is nonsense, the sump doesn't protrude more than half an inch below the chassis rails. The exhaust is the lowest part of the car, and that is mounted the same as the 1275.


Malcolm Le Chevalier

:) you too - and you've moved I see!

I've driven both - autotested both as well - and have enjoyed both in all sorts of situations, so I can be totally unbiased :)

It is - you can drop the 1500 right down to the same as the 1275 - if you do it right - and both of them will scrap their ar*es on the sleeping policemen ;)

A-series guys, what do you rev your engines to whilst driving about anyway? :-)

Malcolm Le Chevalier

Standard - or competition ...?????

You're right though - on general driving, that is a question that would have to be asked. For which, you then lose the fact that you can corner in 2nd in a 1500 which you'd likely have to drop down to 1st in an A-series - and, again, at that point, you are dealing with the non-synchro first gear .... which, ok, that's not the end of the world by a longshot - but heck - it's nice to be lazy sometimes :)

I love both of them - for different reasons - and the likes of Will Corry and the Walbran's k-series cars are pretty awesome too - just kinda glad you can do so much really with a wee car that has lasted well beyond it's sell-by-date and allows you to make so many friends and have such good fun ;)

I was talking general road going engine.

my 1500 revs up to about 5500 but then runs out of puff. that is with standard exhaust manifold tho. upgrades going on at the moment for more horses :-) it has balanced bottom end and hot cam. that is about all you need on the 1500.

but think we have drifted off topic... :-)

Malcolm Le Chevalier

Nice to see the BBS hasn't changed that much ;)

I agree though - I don't normally put the A-series above 5500 for general driving - but can't speak for anyone else.

Look forward to seeing what you do with your engine :)

The relatively low down torque of the 1500s is what makes them so suited to the overdrive conversion.
Guy W

I kind of cheated with my car too, as it has no bumpers or extra supporting steel work it is a 1500 superlight! ;-)

currently working towards putting on a Spitfire manifold etc. the reasons for which are rather long and complicated!
Malcolm Le Chevalier

IIRC I used to rev the various A series I had to about 6500RPM but in the heat of an autotest or hill climb that could hit 7000RPM as the limit was mainly the audible noise and wearing a helmet for the events limited that input. The smoothest revving engine I built was a 1215cc Imp pistoned 1098 as the pistons were quite light compared to the standard A series and a joy to drive, the most powerful was the 1420cc which is a big mains 1098 cranked 1380cc and probably not far off the 1500 for torque.
David Billington

I edited my last post but too late, I added
Regarding the A series gearbox I ditched that in favour of a 4 speed Ford box with synchro on first, I found a lot of problems getting a good A series box in the mid to late 1980s so the work to fit the Ford was a blessing and Ford boxes were cheap as chips at the time, IIRC I ended up with a Escort Mexico box that had much better ratios that suited a light car like the sprite.

In the odd hill climb the 1st synchro was an advantage with hairpin turns, a mate with an A series box had to be trailered home after his laygear tried to make a dash for freedom out the side of the gearbox when thrown into 1st. IIRC at the same hillclimb, Cricket St Thomas near Chard, I saw a Sumbeam Talbot blow up at the hairpin and one of the marshalls walked back towards me with a piston in his hand which had been thrown out of the bottom of the engine.
David Billington

I think I was doing about 7500 in top when the crank broke.

Dave O'Neill 2

Blooming heck Dave - that was quite a break :(

I, Malcolm, am having to face the reality of having to add weight to downgrade Flake :( Still, never mind, it's adding to a whole new area of knowledge, for me, adding weight means chucking some lead weights into a saddle bag .....! :)

Hope that Mr Fisk got his answer - and it's nice to see the thread-drift is still alive and well :) I fear s/he may be totally confused now though as to what to do :) If s/he is in Suffolk though, there's some excellent car clubs who do autosolos, so hopefully, when it's completed, we may see the car out there and boosting up the numbers :) Good luck

Yes, I still haven't found the piston.
Dave O'Neill 2

Now that this thread is basically dead I'll add my 2 cents.

Yes 1275 swaps into 1500 shell fairly easily. I did it because a 1275 is what I had.

Here in the states when I encounter a high mileage and unrestored midgets (over 80,000 miles) I find the 1275's still have good life in them and the 1500's are almost always toast.

...and there are plenty of torque filled V8 classic cars here, but I enjoy the high reving 4 cylinder classics.
Trevor Jessie

This thread was discussed between 19/02/2016 and 22/02/2016

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