Author Topic: A+ engine  (Read 1563 times)

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A+ engine
« on: September 21, 2010, 08:38:26 AM »
I keep reading about A series engine's & A+serie's
The A serie's I can understand, it's just the type name of the engine, BUT what does the A+ serie's meen ?
I'v had a search on the site, but cant find anything.
Can anyone Please Xplain.....



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Re: A+ engine
« Reply #1 on: September 21, 2010, 09:35:44 AM »

A+ engines were a bit of an upgrade on the old A series.  They look much the same, but there were subtle changes to improve.  They started about 1981, so were never officially fitted to Aussie built cars. 

- Block was modified slightly to improve oil flow and add strengthening ribs.
- Gearbox casing had extra strength added too.
- The primary gear, drop gear and input gear between teh crank and gearbox have a differnt tooth profile. 
- Various bearings in the gearbox were changed.
- Clutch and flywheel changed design to reduce pedal effort. 
- Distributor mounting was changed from two bolts and a clamp ring to a fork and bolt arrangement.
- Alternator mounting was moved closer to the radiator, as tehre was no need to allow for a longer generator anymore.
- A double-row timing chain was used on all engines(?).
- The breathers were modified. 
- The bypass hose on the water pump was deleted. 

Probably other things I've forgotten!!

Essentially a complete A+ engine and box will bolt in where an A series was.  Mounts etc are the same.

An A series engine will fit an A box and vise versa, but the primary drop and input gears will need to all be either A or A+.

An A distributor will not fit an A+ block witout mods and vise versa. 

Cranks, cams, pistons, bearings, heads and most internal bits interchange between the two. 

The A series Dyanamo bracket (from pre-Alternator cars) is used on the A+ blockd for the alternator.  So you can use an A series alternator on an A+, but not a Dynamo/Generator. 

The extra breather on an A+ timing cover can cause fan clearance problems on an Aussie Mini/Moke as the later pommy cars placed the radiator and fan further from the block.  A bit of GBH with a hammer on the breather helps.  :)

Brett Nicholson (bnicho)
1971 Morris Moke - Mopoke
1965 BMC Mini Diesel Tractor
1965 Morris Mini Traveller - Trixie
1966 Austin Mini Super Deluxe - Audrey
1973 Land Rover S3 88 inch - Gilbert
2007 Land Rover Freelander 2
2013 Toyota Prado


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Re: A+ engine
« Reply #2 on: September 21, 2010, 11:06:11 AM »
bnicho's list is very good however I would like to add some corrections.

The A+ was introduced in 1978 / 1979 as part of the development for the Austin Metro. They didn't want to spend the money and didn't have the time to develop a new engine for this (so called) world car (which we never got out here!), but they did spend GBP30 millions on redeveloping the A series in to the A+ (the total Metro development cost was GBP 650 millions).

The A+ Gearbox was actually fitted to Australian Mokes from late 1979 (these were available and fitted in the UK cars from 1978). It has an up-rated Layshaft (the small end is bigger) and an up rated Mainshaft (the spigot bearing is bigger), the drop gears had finer teeth with a higher helix angle to quieten them down and the bearings for the idler gear increased. There were on going further developments with these gearboxes for several years which also resulted in the gearcases being modified, the outrigger bearing increased (for the Metro Turbo) and eventually the gears themselves were changed to provide not only different ratios but a higher helix angle to make them quieter. The diffs at an early stage also had a different tooth patern.

The A+ Engine was introduced late 1979 and fitted to Australian Mokes from around that time, both in 998 and 1275 versions (they did make a 850 version in the UK for fitment to the Metro Van). bnicho has covered most of the changes however only a single row timing chain was used, but it now included a decent tensioner. The water pump / cylinder head by-pass was deleted, however this happened at a much later time. The Cranks, con rods, pistons, camshafts oil pumps and cylinder heads while completely interchangable with early engines were different too.

They did change the clutch design, again at a much later time in the A+ history to what is commonly known as the verto clutch. I have not had a lot of experience with these, however many who have had them say the earlier clutch while heavier on the foot is better.

Which is better?

Well, for most normal use, the engine you already have. For all out performance the earlier blocks but with the A+ internals.
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Re: A+ engine
« Reply #3 on: September 21, 2010, 04:42:03 PM »
Thanks gents. Great answers



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Re: A+ engine
« Reply #4 on: September 21, 2010, 10:47:46 PM »
Smoken put up a really good post here on how to physically identify the differences between the two (without pulling them down)

« Last Edit: May 13, 2011, 08:42:49 PM by Newie »


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Re: A+ engine
« Reply #5 on: September 22, 2010, 09:07:44 PM »
On my engine block it is written A +, i was wondering if it was a 1275 engine lol
so i have an A+ engine on y AEM Scout, :)


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