Cylinder block A or A+
Turbo Mini Forums

OK, I have decided to have a go at a Balls out 998 turbo for my hillclimb car.
Initially what I would like to know is, bearing in mind that newest is not always best, what advantage does the 998 A+ block have over the earlier A block. Assuming both are thick flange blocks?
Your help will be appreciated.
Regards
Dave

In practice, fuck all. Choose whatever you most easily can get a dizzy for. If using a std turbo dizzy, use an A+.

a friend of mine builds very good mini7 engines and as fas as i know he always uses A+

there may not be much if any real difference but if going balls out i'd go for an A+

I'd use the A+ purely because the drop gears bearings are better/stronger.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Thanks for the quick concise replies.
Vegard, Perfect use of Anglo Saxon by a Viking, love it. I will be using a mapped ignition so the distributor is not an issue.
Will, I hope this should help with the potential drop gear problems.
(see picture).
I have just spotted in the Haynes Metro manual that the differences were :- hardened crank and hardened valve seats but no mention of the block.
As you have probably figured, I already have an A block and being a tight yorkshireman I want to use it but I am prepared to be talked out of it if someone can give me a reason.
Regards
Dave

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On 5th of Jan, 2007 at 03:09pm Vegard said:

On 5th of Jan, 2007 at 02:08pm wil_h said:
I'd use the A+ purely because the drop gears bearings are better/stronger.

But, that has got fuck all to do with the choice of block

Edited by wil_h on 5th Jan, 2007.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

If you want a "Balls out" engine you want the stiffest block available.

The most significant difference between the A and A+ block is the stiffening ribs on the A+.

I'd suggest it would be best to use the A+ for that reason alone.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Axel, I am aware of the stiffening ribs on the A+, But, I have to say it Does not necessarily mean the A+ is stronger because the ribs are there. Did BL reduce the casting thickness to save a kilo or two of materiel by using thinner castings an add a few ribs on the outside to add a bit of strength back?
Anyway it does not seem to be a problem which ever block is used so I think I will go with what I have.
Thanks for all your replies
Regards
Dave

clever choice

It's said, however not confirmed as I know about that A+ block are made of an inferior material to the A. The ribs are there to counteract this.

If BL did something new in the 70ies, it was not to improve anything, bar save money. This is a fact. If this concerns blocks we do not know.

Do you guys think that BL had problems with block stiffnes on the standard 1275GT or in this cae the Metro?? Never!

How can we measure this once and for all?

Vegard, Totally agree with you regarding BL.
My opinion regarding blocks is that once the thick base flange was adopted to prevent oil leaks between block and gearbox the only improvements that could be made would involve a major redesign (expensive).
It is interesting to note that on the change from A to A+ Turbo no major improvements were made.
If BL engineers recognised that the A centre main bearing was a problem and fitted a non grooved lower shell, why did they not improve the centre cap and its locating (too expensive?).
AS far as I can see the only improvements made over a standard engine for turbo use was 1) a sodium filled exhaust valve. 2) a 3mm larger first motion shaft outer bearing. 3) a non grooved lower shell. Hardly cutting edge. Look at the Dihatsu 3 cyl 999cc Turbo.
Anyway Rant over and back on topic.
I suppose that the only way to check is to section an earyl and a late block but I think it all may be a pointless exercise as both blocks appear to be adequate for any use we may put them to.
While we are on the topic of blocks can anyone tell me why it is considered necessary to tap out the box to block fixing scew holes to a larger size?
Turbo Shed, Could you ask your engine building mate for the specs of his Mini 7 bottom end build, please.
Regards
Dave

WWW.FORCE-RACING.CO.UK PLEASE CLICK HERE

Spot on Carl, It's British Racing green So it should last even longer
Yes?
Dave