Looking at getting a C20XE rebored to 2.1 during a full rebuild, just wondering what the costs involved for a rebore are, and also what pistons I'd need afterwards?
Some people have been saying about using 88mm pistons from an Omega, but what about valve clearence, as have seen a few pictures & noticed they poke slightly out the top of the block, unless its just the pictures I've seen!
Also what else would beed changing/altering to accomidate for the rebore (cams, ecu, etc)
To get it to 2.1 (2092 cc) you will need a rebore to 88mm. I don't know if you can get standard pistons that size (I doubt it)?
The pistons are not from an Omega, they are made by Omega and places like SBD, QED can get them in 88mm for you although they are quite expensive. If your looking to running standard cams just get the 'basic' pistons. If your going lairy with the cams get the 'High Intruder' pistons. They have huuuuuugee valve cutouts and well basically take any cam you throw at them.
88mm pistons will give you just under 2.1 - that's the max you can go.
omegas that size are not easy to source though - try SBD for starters (www.sbdev.co.uk) - they will also advise on CR.
cams - although the omegas will likely have cutouts to accomodate wilder cams - your ECU will not, due to the airflow meter not liking longer duration - unless you use a new ECU to get rid of the AFM, you will be limited to cams which increase lift but not duration - which although will give a little more power are not a good solution due to the extra stress on the valve train they introduce - but as long as you ensure it's in good condition (especially the lifters) they should be ok.
best thing you can do during a rebuild is get some head work done though - extra power with no tradeoff.
rebores are usually between £50-£100 - make sure if you're dropping omegas in you advise the shop you will need a hone to suit moly (harder) rings.
not sure of the exact difference in the hone - but because they're harder it needs to be a decent one, to make sure they bed before it's gone.
just as important is the running in as well.
don't get me wrong - it's not like you need to go dance naked under a full moon with cow dung on your head and a daisy up your butt (like at the weekend) - it's just that harder rings have a smaller 'envelope' to bed properely in.
I wasn't aware Omega pistons were actaully a manufacturer! My bad!
Just looking on the SBD site, there seems to be 2 different sets of the 88mm, XS and SLS
But it doesn't say what the main differences are between them, if any, so does anyone know of this?
Also how much do these normally go for, where you said 'expensive' I assume probably in the region of £800???
no, avoid slipper pistons unless you are really concerned about squeezing hp out of it - i.e 270+bhp
you need to think carefully about what final spec you want - what sort of power, where you want it, and what you're going to use it for.
for a road car that would double up as an excellent track weapon or weekend sprinter, tb's + a mild cam upgrade would be perfect - the minute you start upping the compression or going beyond 285 degrees or so duration, the power curve starts to extend at the top at the expense of low down torque - and to get the best out of that sort of engine you need to go beyond 7750rpm - then the costs really shoots up, and engine longevity goes down.