Hi guys

probably a silly question for those of you in the know.

I was chatting to a mate today and we got to wondering whats the difference between an A series engine and an A+?

Cheers

Kevan

The A+ had some "webs" cast across the outside of the block for strengthening but I've heard that was because of the poorer quality cast iron they were using . The distributer is held in place by a fork shaped bracket held on by a single bolt rather than the conventional mini motors clamping bracket . I'm sure there are more , internal changes as well but that's all I can think of at the moment ....

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The block webs make up for the fact they took metal away to make block lighter.

Comparing just the 1275 hardware, differences on A+ vs an 1100S are-
A+ cranks are rolled fillet radius
conrods are lighter
timing chain is single not duplex, but it gets a tensioner
heads flow a bit better, as ports are bigger
oil pump is slot drive
manifolding is better
many blocks were sleeved at factory due to porosity in the casting.

The best NA A+ for power was the MG Metro, it had 72HP I think, with a single HIF44 carb.
Still 6HP short of a Cooper 1275S...

<edit> most bits out of an A+ can fit in an A series and vice versa.
Heads are interchangeable too.

If you are building a big motor, the 1100S block bores out better.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

On a matter of preference I got A-series. It's readily availiable in Aus due to being sold here locally. And of course the 'S' heritage. But both are 4 cylinder, OHV motors, with 5 port heads. So really it doesn't matter.

But on topic I have looked into this and what I figured out was that it's a lot of subtle things, or simple things.

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

A+... more modern, not as 'ravaged' out.

Usually have been more looked after also - less bastards have touched it so that must be a good thing!

My hot 1310 build has majority A+ parts.
Engine was a 1996 injected.

I won't bore you or other people with the specs.
(unless you want to know them)

The A+ Gearbox is less noiser

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Thanks guys, good to see others are hanging around the 'puter instead of working!

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'62 Morris 850 (Marion)
'65 Mini Delux - sleeper 1275/S discs (Ms Plum)
'69 Vanden Plas Princess 1300
'71 Wolseley 1300
'74 Austin 1300 Countryman
'94 XJ6 Sport 3.2
'04 Rover 75 CDTi

...and has crap ratios you can't do much about- no just tossing S gears in.
... and because the A+ helix angle is greater, gears are probably weaker than the pre-A+.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Oh no willy please tell.

Have you got A+ crank? I've heard the tuftrided A+ cranks are really good, but are they as good as my Nitrided EN40B?

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

I do have an A+ crank.
It is big journals, as are all 1275 A+ cranks.

It is wedged, cross drilled, and a couple of other tricks done to it (GR spec).

I believe that strengthening processes do not work on A+ cranks due to their metal composition.

Someone will be able to verify this, but I am unsure on which process does not have any effect on the crank.


Cranks are very strong... it is the driver that makes them weak

Tuftriding is better for A+ due to, as you say the 'metal compostion'. But Nitriding is better for A.

But the A+ would be fine for performance right?

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

Absolutely.

Being a big journal, it should have the big journal stuff done to it...

Wedging is the major thing... if you want it to last.
Or if you are going to give it the beans for most of its life

There are other tricks to big J cranks that can be done to prolong their life/make them stronger.


As a side note - most of the racers in the UK use big J cranks - so they mustn't be that bad

Your right about most racers using big journal cranks. When i was 1275 shopping I looke at what the UK people use and for racing they seem to go A+ all the way. Well most of the race cars are Rovers but that's beside the point. This would be beacuse of the lack of MK1 components and due to more modern technology.

Thinking about it, A+ must have a purpose. If the A-series was better then they wouldn't have changed. The saying "If it ain't broke don't fix it" comes to mind but in reverse. Although, I don't think there was anything wrong with the good ol' A motors. It's just that it's old technology and A+ is a modern twist on the same idea. Plus the MPi's have distributor-less igntion which is definitely a modern thing! Put it this way, would spend new car prices on a Rover mini with an engine designed in the 50s which hit it's prime in the mid-60s in rallying? I wouldn't.

Having said all that I'm happy with my MK1 'S' motor, and Mini K gearbox. When I bought it, to me, it felt more appropriate for my car than an A+ would have been.

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

Slinkey,
EN40B nitrided S cranks are and were fine for racing, when nearly new.
Many people won't use them for racing now as they are 40 years old and brittle and can go BANG if revved hard.
But for a roadburner, they are fine. They don't wear much at all, my current Mk1 S crank (-.010") is now in its 3rd motor build. I would have ground it, but it was still shmick.

Yes, the Poms use only big journal cranks to race a 1300 with. Not many do over here, from what I see. Maybe `coz we have more A series motors with Mk2 S or 1100S small journal cranks.

A+ cranks (EN16T) can be tufftrided or nitro-carburised, but nitriding them is a waste of time. Wrong metal spec.
see http://7faq.com/owbase/ow.asp?SurfaceHardeningOfSteel

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Agreed about the small J crank bit... it is becoming harder and harder to find a decent sized, uncracked small J these days.

A+ are the way of the future, and will see a longer survival of the beautiful A-series engine.