19 replies to this topic

[PIIIOWW]

This question may have been answered before, apologies if the answer is already available in the threads.

How many types of A-series block are there? I specifically mean block types rather than how many variants of engine capacity are there i.e. removing the crank from the equation.

For instance, are 850s, 997s and 998s bored from a small size block and 1098s and 1275s bored from a larger block? Or did each of these engine sizes have a specific block cast? I’m guessing there are only a few types and they are bored differently...?

[nicklouse]

simplistic terms there are two. small bore 850-998-1098 and large bore.1275 (970-1071-1275)

 

thene there are a few different versions if you look at NONE UK made blocks. EG the SA 1100 which is more like the 1071 but uses a block more like the MPi.

 

 

But it really depends on the reason for your question.

 

IE. S blocks have different main bearing sizes.

 

Autos need extra work to make them usable on a Manual set up.

 

etc

[PIIIOWW]

Excellent. Thanks

[GraemeC]

Do you mean A-series and specifically not A+?

 

There's big bore with and without tappet chests.  Also the Allegro type which is a different casting  

[nicklouse]

  Also the Allegro type which is a different casting  

 well hardly.

[GraemeC]

Is the Allegro not the one with the horizontal oil filter screwed directly to the block?

[Tones61]

Mpi block,no dizzy hole,etc

[PIIIOWW]

Do you mean A-series and specifically not A+?

There's big bore with and without tappet chests. Also the Allegro type which is a different casting

I did actually mean to include A+ in the question but was mainly wondering if all bore sizes were produced from a number of castings. Nicklouse answered the question but I was still left wondering why a 1098 would be prepared from a small block and a 970 and 1071 would be manufactured from a large block. Is there any reason for this?

Edited by PIIIOWW, 09 January 2020 - 08:32 PM.

[nicklouse]

 

Do you mean A-series and specifically not A+?
 
There's big bore with and without tappet chests.  Also the Allegro type which is a different casting

I did actually mean to include A+ I'm the question but was mainly wondering if all bore sizes were produced from a number of castings. Nicklouse answered the question but I was still left wondering why a 1098 would be prepared from a small block and a 970 and 1071 would be manufactured from a large block. Is there any reason for this?

 

every reason. the 1098n is a long stroke version of the 998 while the 970 and 1071 are short stroke versions of the 1275 with all the inherent pros and cons of each.

 

note in the S engines the 970 was first. and was made to suit circuit racing and the rules and regs then present. as was the 1071 they then found themselves in Minis.

[timmy850]

Big bore means room for bigger valves, which is good for racing

 

I also remember reading that your road tax classes were based on the bore of the engine, which skewed passenger engines towards small bore and long stroke

[Ethel]

There's a half decent Wikipedia entry for the A.

[DeadSquare]

There was water all the way round all the cylinders of the 803 block.

[Ethel]

Interesting,

 

I wonder how many different castings/moulds were actually produced?

 

Do they all fall in the 2 basic flavours of ones that'll fit all 1.75" mains bearing cranks & those for 2" mains?

[timmy850]

There would be countless variations. FWD, RWD, thick flange, thin flange, big bore, small bore, tappet covers, no tappet covers. Then there is the A+, MPI, etc

 

More reading here

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

[DeadSquare]

And don't forget the Nuffield 947cc diesel engine.