12st oversize pistons

[jimbob-mcgrew]

ive seen +0.5mm and +1.0mm around - (78.3mm and 78.8mm)

can you get any bigger. like 1.5 / 2.0 ?

[mowgli]

not unless you get custom ones made...

or maybe you can use 1600 or 1800 ones??

[jimbob-mcgrew]

i thought about the 1.6's (79.0mm+), but i think the gudgeon pins are a different size. 18mm vs 20 mm ?

is there anyway round that ? ... like using adapter pins, or different rods or so ?

smallblock 18.'s you mean i take it. they might be the same, larger size 20mm pins.

another thing im not familiar with ... whats the score with headgaskets when you get oversized bits ?

[mowgli]

Jimbob, follow the link on my sig & have a damn good read of the piston catalogue.. look at vw/audi & bmw for a start.

as for the gudgeon pin sizes, a decent machinist will be able to make the 18mm holes bigger, then re-use the old pins..

1800 small blocks use 18mm gudgeon pins

as for gaskets, use the e16se/z16se one.

[jimbob-mcgrew]

1.8 uses 18mm - oof !

cheers, will do :thumb:

[dgbnova#1]

Things like this make me smile lol been looking at civic forums for bits for my mates car what a load of tossers they are had no idea
on here fairly tech question answered job done

[mowgli]

the thing about a nova is that a tech question is most likely going to be covering old ground, and we aren't afraid to do some DIY on them. whereas the civic lot are worse scene whores than the veedubbers & don't actually dare to DIY their cars for fear of upsetting the other scene whores...

[dgbnova#1]

Your not kidding they are all my vtec not working ?????????
answer----------- let it warm up

post over !

its tragic

[Andy]

Vtec failed at the lights yesterday what shall i do?
Gas yourself

[jimbob-mcgrew]

have a damn good read of the piston catalogue

i had a good scan through.
i mis-read the haynes. i thought the 12st was 18mm, but its larger, and longer @ 20mm x 65mm, most of the compatible's are 18 x 55.
the later gen corsa 1.2's are the 18 x 55 type, and have a 10.5mm longer stroke.

i suppose tho, like you say, the pin hole in the piston can always be widened, and the pin cut down 10mm to fit.
i did some calculations and with z18xe pistons @ 80.5mm, the cc would be 1281, up fromm 1196.
the 1.8 flat top pistons are low profile, and alot shorter, so the block would need decking approx 5-6 mm, ontop of the 80.5 rebore
they look fairly skeletal by comparison too, so probably weigh a fair bit less. might help with revs.

will the 1.8 head gasket fit all the smallblocks ?

it seems more worth doing it to the later gen engine, as you gain 300cc instead of just 85. but that engine's probably longer, and weighs more.

just a random idea i had, as everyone seems to write off the humble 1 point poo.
i thought a factory looking 12st under the bonnet, with close to 100 donkies, would be something different. and being one of the lightest blocks, handle about as good as a nova can.

[jimbob-mcgrew]

are the X and Z generation bottom ends aluminium/lighter ?

[peester]

All small block X and Z generation blocks are Cast Iron. On the X/Z18XE/1 the engine/block itself shouldn't be any taller - it appears to sit and fit in a Nova engine bay as per usual. The crank does sit a tad lower out of the bottom of the engine though, so the sumps are a bit deeper. Bottom end wise I wouldn't think it is any heavier that the old 8 valve blocks though. More metal has been removed for bores! ha.

[mowgli]

1.8 gasket is a slightly different shape so is no good. The 1.6 one is quite big so should fit ok.

To get proper power, using a 1.6 bottom end as a start would be good.