25 replies to this topic

[Guess-Works.com]

makes no difference to cc the deck height, only to the compression ratio, which would depend upon the stroke of crank, length of rod and also pin to crown height of the piston.

[mk3 Cooper S]

More confussed now.
If you have the same bore and a shorter stroke your would have a really poor CR if you did not deck the block? A I missing something?

[Guess-Works.com]

Yes, you use longer rods.... hence why the 970s engine had different rods to the 1275s engine..

with relation to the offset crank grind, the most it can be offset is about 1.5mm which can be taken up by decking the block or using a piston which has a taller pin to crown height.

[mk3 Cooper S]

A bit of progress.
I have wraped the crank journals with tape to protect them and done a loose assembly using a standard 1275 crank.

I have pictured the position of the pistons at the top of the stroke.

Looks good to me so I am pretty sure I have a 1380.

What do you reckon?

 IMG_0888b.JPG   62.54K   14 downloads

Also J & J Mini's, anyone know anything about them ?

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Edited by mk3 Cooper S, 18 December 2012 - 10:54 PM.

[holmesy]

I like how the pistons have standard on them

[Guess-Works.com]

The 73.5mm pistons are a std size, just not for the A series engine...

[holmesy]

what where they standard for

[Guess-Works.com]

Can't remember, but 74mm pistons were actually from the Ford 1.1 CVH engine.. 74.5mm the Triumph 2500and not forgetting the small bores use Imp pistons as an oversize option.

[mk3 Cooper S]

I thought from memory that they were Triumph std size

[holmesy]

ive got 5 forged cp pistons laying around but think they are too big for a mini plus you would need longer pistons as they are short skirt customs, will find out what size they are, might be of used to someone as i fried one piston and would of cost 600 for another to be made so got another set the size up for 1200

[holmesy]

believe there 83mm no good for a mini lol