30 replies to this topic

[Mite]

Historically it was a challenge for the company to productionise the 1275cc and remedy the initial issues for uses outside of the 1275 Mini Cooper S. While it is generally accepted the engine could not be enlarged any further, with Vizard's book as well as the fully rebuilt David Brown Mini Remastered engines up to 1330-1380cc (with new internals to a improved specification) in mind. What was the most plausible enlargement beyond 1275cc the production A-Series could have received during the course of the engine's long run between 1293cc to around 1380-1399cc+?

 

Was it a case of the limitations of the existing engine (and later A-Plus) itself as mentioned in previous threads and elsewhere preventing it full stop or something that could have been revolved with new production tooling and other changes, similar to how the South African version of the UK built Ford Essex V6 was able to use the new tooling to enlarge its locally built Essex V6 from 3-litres to 3.4-litres for road-going models?

 

If the latter then theoretically could such a solution have been possible on the South African built versions of the A-Series engine had BMC South Africa been more ambitious with the required financial backing behind it?

[Minigman]

I’m sure Vizard mentions 1600cc versions of the A Series in the yellow bible. Most stroked ones are 1430cc these days.

I guess cost and reliability were the main issues production never went beyond 1275cc. That said the 1275cc with a decent head wasn’t slow in its day compared with modern cars.

Edited by Minigman, 29 August 2020 - 04:19 PM.

[Mite]

It is not an increase in speed that interests me regarding modifying the A-Series engine's displacement above 1275cc due to its renowned reputation for producing great amounts of power, rather am contemplating whether the 1293-1399cc engines could have been productionised for road-going models as was originally the case with the standard 1275cc engine had enough money been available.

 

Production version of the 1425-1442cc to 1600cc engines would have been desirable had it been possible, yet would have overlapped with other engines the company had. On the other hand perhaps a distantly related linear successor to the A-Series could have eventually reached those displacement limits as has been practiced by other car manufacturers with much success.

 

Had the money been available to resolve the reliability issues and taking the existence of the larger engines the company had into account, would it have been more feasible for the production A-Series to be enlarged to around 1293-1330cc or up to around 1372-1399cc?

[Curley]

What are the rules? Are we limited to using the existing A+ block dimensions? Do you allow for new external dimensions? I'll assuming we're keeping the gearbox and transfer case layout?

[sonscar]

I suspect there was no money and little will.A crossflow head would have been a better investment.The gearbox was always going to be a weak point.The A series and the company were already dead but refused to die.Just my 2p.Steve..

[Spider]

With any production engine, especially of that era, there needed to be a fair degree of conservatism applied to any design.

 

This is to ensure a high degree of reliability, robustness, allow for production tolerances and the ability to recondition the engine (and in that era, it seems at least twice).

 

In regards to the 1275, originally, the factory only deemed them 'safe' to rebore to +0.020" (with a first at +0.010") and at a quick look through the parts books, this was the case to at least 1986 and likely beyond. I'd say this came down to possible concerns over bore porosity, and head gasket reliability. Keep in mind here too that we are talking about mass production units, not bespoke 1 offs, where much more time and attention usually is given and that couldn't be productionised. While the factory capped that at +0.020", personally and taking production methods in to account, I feel they could have sensibly gone to +0.060" over and that's about it.

 

Also, the Crankshafts were also only deemed to be grindable to -0.020" on the Mains and -0.040" on the Big Ends.

 

In production as well, some blocks didn't pass muster and were fitted with liners, so the ability to do that - in their conservative production environment - also needed to be taken in to account.

 

I know that some 1275's can be taken to just shy of 1600 cc, however, the Production Cylinder Heads just couldn't nearly feed enough Air in to them at that capacity and so at this size, they have next to no HP gains over those at 1500, though, they did have a little more low RPM power. With most 1275 Blocks, once you go above (if I recall) about an 86 mm stroke, you also need to start grinding the block & gearbox to get clearance for the Big Ends. Also, when working from Factory Production Cranks, stroking beyond 0.060" (1.5 mm) over standard, requires the use of different Con Rods (Cooper S & Sprite), however, this is going beyond their safe limit of -0.040.

 

Also, keep in mind, they wanted to churn out cars for the masses, including some sports models, with as few warranty issues as possible, as that not only cost them money to rectify, but also loss of reputation.

 

In later years, rather than looking to a bigger engine, they just fitted a blower, and again, in a very conservative way, rather than spend money on effective making a new engine.

 

All the A Series Engines were machined by Transfer Machines (pre-CNC) and many of the suggestions put forward by the Development Department, while sound in every respect, they often couldn't be machined in their Transfer Machines and so they never say the light of day outside of that department as management, to their peril, wouldn't spend the cash needed to up-date and modernise that production line. I think when the Metro was coming in to play and they looked at what to do with the engine, a golden opportunity was lost then to make this move.

[KTS]

Had to look up what Transfer Machines were and appropriately, found this

http://www.austinmem...-128/index.html

[Mite]

With any production engine, especially of that era, there needed to be a fair degree of conservatism applied to any design.

 

This is to ensure a high degree of reliability, robustness, allow for production tolerances and the ability to recondition the engine (and in that era, it seems at least twice).

 

In regards to the 1275, originally, the factory only deemed them 'safe' to rebore to +0.020" (with a first at +0.010") and at a quick look through the parts books, this was the case to at least 1986 and likely beyond. I'd say this came down to possible concerns over bore porosity, and head gasket reliability. Keep in mind here too that we are talking about mass production units, not bespoke 1 offs, where much more time and attention usually is given and that couldn't be productionised. While the factory capped that at +0.020", personally and taking production methods in to account, I feel they could have sensibly gone to +0.060" over and that's about it.

 

Also, the Crankshafts were also only deemed to be grindable to -0.020" on the Mains and -0.040" on the Big Ends.

 

In production as well, some blocks didn't pass muster and were fitted with liners, so the ability to do that - in their conservative production environment - also needed to be taken in to account.

 

I know that some 1275's can be taken to just shy of 1600 cc, however, the Production Cylinder Heads just couldn't nearly feed enough Air in to them at that capacity and so at this size, they have next to no HP gains over those at 1500, though, they did have a little more low RPM power. With most 1275 Blocks, once you go above (if I recall) about an 86 mm stroke, you also need to start grinding the block & gearbox to get clearance for the Big Ends. Also, when working from Factory Production Cranks, stroking beyond 0.060" (1.5 mm) over standard, requires the use of different Con Rods (Cooper S & Sprite), however, this is going beyond their safe limit of -0.040.

 

Also, keep in mind, they wanted to churn out cars for the masses, including some sports models, with as few warranty issues as possible, as that not only cost them money to rectify, but also loss of reputation.

 

In later years, rather than looking to a bigger engine, they just fitted a blower, and again, in a very conservative way, rather than spend money on effective making a new engine.

 

All the A Series Engines were machined by Transfer Machines (pre-CNC) and many of the suggestions put forward by the Development Department, while sound in every respect, they often couldn't be machined in their Transfer Machines and so they never say the light of day outside of that department as management, to their peril, wouldn't spend the cash needed to up-date and modernise that production line. I think when the Metro was coming in to play and they looked at what to do with the engine, a golden opportunity was lost then to make this move.

 

Thanks Moke Spider

 

So a 72.19mm bore would take the 1275cc to about 1326cc, would it be fair to say a further stroke increase to 82.29-83.8mm (the latter as on the 1098cc) be the absolute sensible limit for the production A-Series equating altogether to a total displacement limit of around 1345-1372cc (possibly to as much as 1398cc with stroke below 85.5mm v)? The 1326-1372cc displacements being roughly aligned with the similarly-sized fully rebuilt 1331-1372cc A-Series engines for the Mini Remastered.

 

Though intent this thread to focus on sensible displacement increases the production A-Series could have realistically achieved above 1275cc, how would a 5-bearing crankshaft as in the link below have impacted the potential displacement increases of the A-Series had it been approved for production earlier on or is it one of those unknown factors that nobody yet knows at this time?

 

https://www.facebook...1708914/?type=3

 

 

On the subject of updating and modernising the production line of the A-Series engine within the context of the Metro's development, was it that unwillingness to make the most of that golden opportunity one of a number of factors behind the cancelling of A-OHC?

 

And prior to the Metro approximately what was the earliest point the company could have realistically updated and modernized the production line for the A-Series engine (and others) to take advantage of what the development department was suggesting? Would it have opened up an opportunity for the company to adopt a more linear evolutionary way of replacing the A-Series?

Edited by Mite, 30 August 2020 - 12:08 AM.

[Curley]

The MPI block did have a certain amount of 'money no object' investment from BMW owned Rover. However I suspect this was limited to needing to be compatible with the pre-existing bolt on parts. I believe by this point Rover had long since committed to the K series engine to replace the A series. Rover did try the K series in the Mini so I guess the cost of developing the MPI was cheaper than making the K series fit - knowing Rover had plans for the then coded R50.

 

The internal combustion engine is essentially an air pumps so all things being equal 1.3L is 1.3L. This is why the K-series heads offer so much more power than a 5 port ever will; having benefited from a further 40-50 years of cylinder head design & manufacturing improvements.

 

One thing I would change would be to make a larger hole for the cam as the current bearing ID limits the size of the lobes.

[Ethel]

The cam lobes can be further magnified by the rocker ratio, but there are limitations in the valve train.

 

At 1275cc's the A is in the territory the B Series started in and BMC had the E Series too. I see an absence of motive rather than an absence of means.

 

They got to 1275 with a new block & crank. I dare say they could have gone further by the same route.

[Spider]

 

Thanks Moke Spider

 

So a 72.19mm bore would take the 1275cc to about 1326cc, would it be fair to say a further stroke increase to 82.29-83.8mm (the latter as on the 1098cc) be the absolute sensible limit for the production A-Series equating altogether to a total displacement limit of around 1345-1372cc (possibly to as much as 1398cc with stroke below 85.5mm v)? The 1326-1372cc displacements being roughly aligned with the similarly-sized fully rebuilt 1331-1372cc A-Series engines for the Mini Remastered.

 

Though intent this thread to focus on sensible displacement increases the production A-Series could have realistically achieved above 1275cc, how would a 5-bearing crankshaft as in the link below have impacted the potential displacement increases of the A-Series had it been approved for production earlier on or is it one of those unknown factors that nobody yet knows at this time?

 

https://www.facebook...1708914/?type=3

 

 

On the subject of updating and modernising the production line of the A-Series engine within the context of the Metro's development, was it that unwillingness to make the most of that golden opportunity one of a number of factors behind the cancelling of A-OHC?

 

And prior to the Metro approximately what was the earliest point the company could have realistically updated and modernized the production line for the A-Series engine (and others) to take advantage of what the development department was suggesting? Would it have opened up an opportunity for the company to adopt a more linear evolutionary way of replacing the A-Series?

 

 

 

Keeping mass production limitations in mind, I would say a 72 mm bore x 86 mm stroke would be the limit, but, at that bore size, and taking in to account a conservative production approach, it wouldn't be re-boreable, so, that probably brings us back to 71.5 mm bore. This gives us 1380 cc.

 

I really don't see the 3 main bearing crank the engine has as any kind of limitation and adding 2 more bearings only increases drag. I have seen that 3D drawing elsewhere and it's certainly a novelty. If you look at the Ford Flat Head V8 engines, they were also a 3 Main Bearing Crank   for the most part, quite similar in sizing to the 1275 Crank, only, a little longer on the Big Ends, they also run a Cast Iron Crank. The Hot Rodders are getting up to 650 HP on these parts and more when they go to billet cranks.

 

I don't know why they never went ahead with the OHC Heads, I can only guess it would have been a cost issue. mab01uk I think could shed some light here.

 

I'm not sure if you've read any books on the early history of the Mini, but, right from the start, Issigonis detested the A Series Engine for the Mini, he did tinker with alternative experimental engines, even before the car was in Production, however, he was forced to use 'something that was already in production', again, to save on costs.

 

At the end of the day, keep in mind, the car makers are not driven by fast and exciting cars, or powerful engines, they are driven by profits and costs of production are directly linked to that. Anything they can (usually) do to save even as much as 0.001 pence per item, they'll fight for - it all adds up. In particular, when bringing out new models, it's the styling and features, colours and the doof doof that sell them, not new (and expensive) engines, though, they will 'tinker' with what they already have in production, these days, often keeping the same basic unit in production for 10 to 15 years before doing a major update, all due to the very high costs of changing them when it won't equate to any further meaningful sales.

 

 

 

One thing I would change would be to make a larger hole for the cam as the current bearing ID limits the size of the lobes.

 

Bore them out - easy enough   been done before however, the Cylinder Head is the limitation really.
 

[Mite]

The MPI block did have a certain amount of 'money no object' investment from BMW owned Rover. However I suspect this was limited to needing to be compatible with the pre-existing bolt on parts. I believe by this point Rover had long since committed to the K series engine to replace the A series. Rover did try the K series in the Mini so I guess the cost of developing the MPI was cheaper than making the K series fit - knowing Rover had plans for the then coded R50.

 

The internal combustion engine is essentially an air pumps so all things being equal 1.3L is 1.3L. This is why the K-series heads offer so much more power than a 5 port ever will; having benefited from a further 40-50 years of cylinder head design & manufacturing improvements.

 

One thing I would change would be to make a larger hole for the cam as the current bearing ID limits the size of the lobes.

 

In the case of the K series engine, find it strange that while it was lighter than the A-Series / MPI in 4-cylinder form it also managed to be a bit too inconveniently long to feasibly fit into the engine bay of the Mini despite originally being conceived as a 1-1.4-litre 3/4-cylinder engine. Not to mention its height later on which was brought up during the R50 project. 

 

Notwithstanding how the K series engines was further developed and enlarged to gain its infamous reputation, surely it was within the company's ability to make the K series engine into a more space efficient package as was achieved by other car manufacturers whose similar capacity engines would unintentionally end up being popular and arguably even better fitting engine conversions for classic Minis.

 

 

The cam lobes can be further magnified by the rocker ratio, but there are limitations in the valve train.

 

At 1275cc's the A is in the territory the B Series started in and BMC had the E Series too. I see an absence of motive rather than an absence of means.

 

They got to 1275 with a new block & crank. I dare say they could have gone further by the same route.

 

With the benefit of hindsight there was some value in at least growing the A-Series to 1293cc if not to 1380cc, the latter had it appeared earlier would have given the company a bit more presence in the 1400-1500cc sector when the hefty B series had grown to 1622cc until the arrival of the 1485cc E series though the company did not view it as a pressing need until things were too late to be turned around.

 

 

 

 

Thanks Moke Spider

 

So a 72.19mm bore would take the 1275cc to about 1326cc, would it be fair to say a further stroke increase to 82.29-83.8mm (the latter as on the 1098cc) be the absolute sensible limit for the production A-Series equating altogether to a total displacement limit of around 1345-1372cc (possibly to as much as 1398cc with stroke below 85.5mm v)? The 1326-1372cc displacements being roughly aligned with the similarly-sized fully rebuilt 1331-1372cc A-Series engines for the Mini Remastered.

 

Though intent this thread to focus on sensible displacement increases the production A-Series could have realistically achieved above 1275cc, how would a 5-bearing crankshaft as in the link below have impacted the potential displacement increases of the A-Series had it been approved for production earlier on or is it one of those unknown factors that nobody yet knows at this time?

 

https://www.facebook...1708914/?type=3

 

 

On the subject of updating and modernising the production line of the A-Series engine within the context of the Metro's development, was it that unwillingness to make the most of that golden opportunity one of a number of factors behind the cancelling of A-OHC?

 

And prior to the Metro approximately what was the earliest point the company could have realistically updated and modernized the production line for the A-Series engine (and others) to take advantage of what the development department was suggesting? Would it have opened up an opportunity for the company to adopt a more linear evolutionary way of replacing the A-Series?

 

 

 

Keeping mass production limitations in mind, I would say a 72 mm bore x 86 mm stroke would be the limit, but, at that bore size, and taking in to account a conservative production approach, it wouldn't be re-boreable, so, that probably brings us back to 71.5 mm bore. This gives us 1380 cc.

 

I really don't see the 3 main bearing crank the engine has as any kind of limitation and adding 2 more bearings only increases drag. I have seen that 3D drawing elsewhere and it's certainly a novelty. If you look at the Ford Flat Head V8 engines, they were also a 3 Main Bearing Crank   for the most part, quite similar in sizing to the 1275 Crank, only, a little longer on the Big Ends, they also run a Cast Iron Crank. The Hot Rodders are getting up to 650 HP on these parts and more when they go to billet cranks.

 

I don't know why they never went ahead with the OHC Heads, I can only guess it would have been a cost issue. mab01uk I think could shed some light here.

 

I'm not sure if you've read any books on the early history of the Mini, but, right from the start, Issigonis detested the A Series Engine for the Mini, he did tinker with alternative experimental engines, even before the car was in Production, however, he was forced to use 'something that was already in production', again, to save on costs.

 

At the end of the day, keep in mind, the car makers are not driven by fast and exciting cars, or powerful engines, they are driven by profits and costs of production are directly linked to that. Anything they can (usually) do to save even as much as 0.001 pence per item, they'll fight for - it all adds up. In particular, when bringing out new models, it's the styling and features, colours and the doof doof that sell them, not new (and expensive) engines, though, they will 'tinker' with what they already have in production, these days, often keeping the same basic unit in production for 10 to 15 years before doing a major update, all due to the very high costs of changing them when it won't equate to any further meaningful sales.

 

 

Good to know in better circumstances a mass production A-Series could have plausibly grown to about 1372-1380cc, even in non-performance spec those displacements would have still been pretty useful on a wide range of cars that already used the A-Series engine without encroaching on the E Series or B / O Series.

 

Much has been mentioned about how the A-Series could have plausibly been improved in other areas with OHC or Crossflow heads and more, especially if the production line had been up-dated and modernized earlier on (would a period approximately between the 1950s-1970s have been the most opportune time for it to have been implemented had it been possible?).  

 

Much has also been said on a full replacement of the A-Series being the best way to go based on how history has progressed, which do not disagree though believe it was potentially plausible (in hypothetical better circumstances) for the engine to have been succeeded in a similar linear evolutionary way as with its comparably sized 1.4-litre French counterpart at Renault up to today (with suitable growth above 1.4-litres) or its larger petrol and diesel cousins from its B-Series brother.

 

Am very much aware Issigonis loathed the A-Series let alone the idea of having carry over engines already in production in general over the course of his career, not sure if it was something against the A-Series per se that could have been remedied or because the engine was a constraint as well as an element he had no hand in developing thus making the Mini less of a total work of art in his eyes (and a bit longer than he originally wanted) compared to other designers within the industry who were given more freedom to create their total work of art to cement their place in history.

 

However his experimental engines efforts left a lot to be desired, even if something like the 475cc 2-cylinder A-Series prototype considered earlier on in the development of the Mini might have been better suited in say a much earlier version of the later Mini-Mini project that Innocenti wanted as a Fiat 500 rival had the roughness and other flaws of the 2-cylinder unit been remedied instead of what became the 9X motor. However IIRC (likely wrong here) the experimental A-Series twin itself preceded Issigonis's return to the company and was said to originate first as an in-house alternative to the Joe Ehrlich designed 2-cylinder 2-stroke engined 1954 Austin A20 Lightweight Seven prototype, than later in the "Griffin Goggomobil" proposal before being considered than soon discarded in the Mini project.

[mab01uk]

The A-Series did well to eventually achieve 1275cc displacement in production bearing in mind it originally started life in 1952 as 803cc......but the high cost of the development of the A+ for the Metro (Total cost of A+ development and retooling programme: £30 million) has made little sense to me over the years for what was achieved, when the money spent could easily have produced a 5-speed gearbox upgrade for the Mini and Metro which were to be in production for many more years and with motorway driving by then an essential part of most drivers motoring needs.

Engines : A-Series:-

https://www.aronline...gines-a-series/

 

Interesting extract below from an AROnline 'Mini Development in the 1970's' article about BL's research into the OHC A-Series engine:-

"In April 1982 the Mini was given higher gearing to make it more economical, but this did nothing for acceleration, and the car lost a little of its buzzbox characteristics. The fact that the ancient A-Series engine could cope with up-gearing was a tribute to its remarkable torque characteristics, even in its tamest form.
And that brings us to the subject of why the A-Series engine was never radically re-engineered to modern standards. Was it a matter of cost or were there other reasons?
Back in the 1970s BL had embarked on projects to develop overhead camshaft versions of both the A- and B-Series engines. The reason for this was that MG used both engines and as they exported to the USA where stringent anti-emissions legislation was in force, it was paramount that BL’s existing engines were made more efficient to enable them to remain both legal and competitive by using the more efficient emissions friendly overhead cam layout.

In the end the OHC B-Series evolved into the O-Series engine first seen in 1978, while converting the A-Series to the overhead cam layout proved to be a technical cul-de-sac. The immediate problem of continuing to sell the MG Midget in the USA was solved by replacing the 1275cc A-Series engine with the 1493cc Triumph engine also used in the rival Spitfire. But an OHC A-Series could be used in the ADO88 and other BL cars. In the event eleven prototype overhead cam A-Series engines were built in 1975 using Cooper S blocks in capacities of 970cc, 1097cc and 1275cc. The engines used aluminium cylinder heads.

The engineers obtained the following performance figures for OHC Minis:

970cc: OHC 59bhp @ 6750rpm, 51lb ft @ 5250rpm
1097cc: OHC 72bhp @ 6500rpm, 64lb ft @ 5000rpm
1275cc: OHC 84bhp @ 6750rpm, 80lb ft @ 4500rpm

The above figures look very impressive, and a bluff-fronted Mini Clubman fitted with the OHC 1275cc engine and twin HS6 SU carburettors could reach 100mph. It would be easy to accuse BL of another missed opportunity. But a look at the comparative figures for the existing overhead valve engines reveal another story. For a direct comparison first we will use the three Cooper S engines and then the standard tune single carburettor engines seen in the mainstream production Minis.

Standard OHV Mini engines:

970cc: OHV 65bhp @ 6500rpm, 55lb ft @ 3500rpm
1071cc: OHV 70bhp @ 6000rpm, 62lb ft @ 4500rpm
1275cc: OHV 76bhp @ 5800rpm, 80lb ft @ 3000rpm
998cc: OHV 38bhp @ 5250rpm, 52lb ft @ 2700rpm
1098cc: OHV 45bhp @ 5250rpm, 56lb ft @ 2700rpm
1275cc: OHV 54bhp @ 5250rpm, 67lb ft @ 2500rpm

Converting the A-Series engine to overhead camshaft simply pushed the peak torque further up the rev range and actually caused more problems than it solved. One of the great virtues of driving a Mini is its remarkable ability to pull top gear at low revs, something that was exploited by Austin Rover and later Rover when the car was up geared.
An overhead cam A-Series engine would have been torque shy where it mattered in everyday driving and that was indeed the case with the 100mph OHC Mini Clubman. The modern solution for the lack of torque where it matters would be to add more gear ratios, but BL’s engineers decided that a reliable revised transmission in sump gearbox was not feasible. Therefore the decision was taken to opt for the A+ programme. BL had already burnt its fingers with the OHC E-Series engine. The E-Series had been intended to supplant the B-Series, but its lack of torque resulted in the old B-Series going into the Marina and Princess, and even the O-Series was a disappointment. BL would not make the same mistake again."
http://www.aronline....history-part-2/

Edited by mab01uk, 30 August 2020 - 02:19 PM.

[mab01uk]

Alec Issigonis wrote to BL boss Donald Stokes 18th April 1968:
"The greatest need in combating increased production costs over the year is the development of a new engine for a small car of the Mini type. The present A-Series engine offered a quick way of getting the car into production in 1959, but has now outlived its purpose both for weight and cost compared with European competition."

However these proposals were kicked into the long grass by British Leyland who were not interested in technical excellence or innovation at a time when they wanted Austin-Morris to return to financial stability and profit.......

The Alec Issigonis 9X engine from 1968

 

[Curley]

Which book is that photo taken from?