28 replies to this topic

[ministox man]

sorry mate i meant mini sprocket bit of trouble reading stuff

[DANTOO]

SO guys.... im confused lol

I just saw on ebay someone put....

"THESE ARE A SET OF FOUR PISTONS COMPLETE WITH RODS OFF A 1275 ENGINE

THE PISTONS ARE MADE BY AE AND THE NUMBER STAMPED ON THE PISTONS IS 21251+060.

PISTONS ARE FITTED TO RODS.

THIS GIVES YOU A 1340CC ENGINE"

Do you not have to get the engine bore out to get a 1293, or 1340? but if you do.. do you have to change the crank?

[DANTOO]

oh i see! I think ive just clicked lol


so when you want pistons for a 1293... you want say "1275 high compression +00.20"

and that will fit the 1293? ... im getting there i think

[Pavel]

Yes. your standard engine is 1275 cc and 70.6mm bore. To go to 1293, you bore out the block to extra 20 thousandths of an inch, and need the matching pistons (+20 pistons).
If you want to go to 1310, you do the same but +40 thousandths, if 1340 then +60 thou.
1380 is got by using 73.5mm pistons, and boring the cylinders out to this size as well.
Crank doesn't need to be changed for any of these

[pikey7]

 Mini_engine_sizes.txt   31.5K   26 downloads

Save the attachment, rename it as .xls, and open in excel. It shows most combinations of piston and crank sizes, plus on the other "tab" is a compression ratio calculator.

'tis just a guide though, so if anythings wrong, dont whip me too much!

[DANTOO]

Cheers guys!

I was reading that huge yellow "How to tune an A series engine" last night.

I never knew you could get the engine to nearly a 1600cc! lol

but its not very wise... ..... booom!

[Leonard]

pikey7, 1275 crank stroke is wrong on that sheet, but i wont whip you too mcuh!

[pikey7]

good! I hate pain!

What's it supposed to be then?

[Leonard]

sorry my mistake i was looking at 1257!!!

[Clubby1275GT]

sounds to me like the chap in question does autograss, my mate was big into it at one stage, used to do class 1, and tried to squirm every bit of power out of it as possible as u cant really change anything apart from needle and slight head skim. something was once mentioned about ford fiesta pistons (slightly domed maybe?? didnt really listen to all of it, anyone ever herd of anything like that??

[ministox man]

never heard of the fiesta piston thing

i do O.R.C ministox you can do a bit more like cams and valve seat angles and some other stuff

[Stiggytoo]

Sorry to open up this thread again, but I have a similar dilemma. I have some flat tops and hepolite 20773 +60 dished pistons. I also have a pocketed block and a 12g940 head to go on it.

I have read that the dished pistons are rated for about 6000rpm. Do you think I would benefit from revving higher and would flat tops allow me to do this? What would you recommend? 

Thanks   

Edited by Stiggytoo, 24 July 2013 - 09:35 AM.

[Ethel]

The dish isn't as important as the quality of the piston. You'll certainly want to rev beyond 6k if you want any sort of power out of a small bore. A standard 12g940 has a few cc's less chamber volume than the normal 998 head. You'll need to sit down and do some sums to work out the best compression ratio, but it should be achievable with either flat or dished. I'd expect flat to be easier, particularly if you use a wilder cam & want to work the head a bit.

[Stiggytoo]

One final question. I've also got some pistons from an old A series engine, with markings 'M2039 U53.' Any chance they would be more suitable in terms of peak revs etc?