12 replies to this topic

[seb79]

hello

i try to rebore engine in order to build a 1380 cc !

But i have got a big problem. Impossible to find a block able to be rebore
I used two engines 12he25 : but the result is porous cast iron !

On monday, i will try a 12a2a engine in order to succed to rebore this one.

My question is : why the shops never explain this problem when you buy pistons. It's very disapointed to use a lot of engines in order to succed to build a good engine.

Have you got informations about this problem ?

thanks for your fast help !

[Jammy]

Are you doing the rebore yourself? I believe you have to offset the bores when going out that large.

If you can try and find a 1300GT block/engine.

[ginigwunkle]

yeh was goin to say, you have to offset the bores,

also helps with cooling, although i believe offsetting is for clyinders 2 and 3 as the gap is nearly nothing!

esp with 74mm pistons on the 1430!

[Retro_10s]

Porous blocks eh,.. Hmmm I don't think there's much you can do about it mate other than get the bores linered,.. but you wouldn't be able to take it to 1380 at all. Porous blocks (correct me if i'm wrong) are just one of those things,... it's always a risk when using an Old cast iron block.

Just keep hunting. Oh and a 1300GT block would be an Aseries I believe. I thought It was best to Keep things as large as 1380's to A+ but again,... this could just be another one of those " if you do the job properly it's no problem" things.

[ginigwunkle]

why wouldnt you be able to get to 1380?

my bores are lines and ther 74mm....

[Sprocket]

I doubt you will have a problem with the 12A block, these are 1992 onwards and were cast with more modern processes. The Cast cores are the same, but the way things are made isnt.

Just out of curiosity, did these porous blocks have WFM 1024 cast in big characters on the front of the block just below the head??

There is another thread not long back discussing this very issue, mainly starting with a linered block, were these blocks linered??

The topic also discussed the offset boring process. Have a search and Ye shall find

[Sprocket]

why wouldnt you be able to get to 1380?

my bores are lines and ther 74mm....

You have a linered 74mm block??!!!

Cant be much metal between cylinders 2 and 3, well not enough to tie in the sides of the block!!

Say the liners are 0.5mm (20though) thick, this would leave 1.5mm of original block between cylinders 2 and 3, not much atall.

Personaly i wouldnt trust it for high output.

[ginigwunkle]

yeah theres hardly anythin left,

but im pushin 120hp and 11(ish):1 compression

no problems at all after 10k!

[seb79]

wfm1024 are written on all the blocks

I will try my last engine : 12a2a who must be a cooper carbi.

After, i dunno what to do... at this moment, i think to sell the car if this engine can't be rebored.........

Edited by seb79, 16 September 2007 - 09:51 AM.

[pogie]

As others have said you need to offset the centre of the bores when doing a re-bore for 1380.

Here is a diagram showing what you need to do to get big bore A-Series engines without braking into the oilways. The diagram is scanned from the David Vizard book, Tuning BLs A-Series Engine. The book is essential reading if you are planning to modify a Mini engine.

HTH

Attached Files

•  Offsetbores.jpg   169.89K   47 downloads

[The Matt]

yeh was goin to say, you have to offset the bores,

also helps with cooling, although i believe offsetting is for clyinders 2 and 3 as the gap is nearly nothing!

esp with 74mm pistons on the 1430!

I always thought that 1430s were a 73.5mm bore (same as 1380) but with a stroked crank?

[ginigwunkle]

well i got 74mm pistons and 84mm stroke crank(std 81mm) and 18cc dish = 1432cc

[Sprocket]

well i got 74mm pistons and 84mm stroke crank(std 81mm) and 18cc dish = 1432cc

Your maths dont add up buddy