O/S Pistons

[**Ghost**]

For the techheads, wots the difference between an oversized piston and a standard bore one? and yes i realise it is probably bigger since its oversized, what i'm trying to ask is

1. does the installation procedure become different? as in do i need to bore out my chambers to fit it in etc?

2. what are teh advantages/disadvantages of each?

[Weq]

yes u need to overbore the cylinders to match. u get weaker sleeves as a resault.

[hondar]

yes u need to overbore the cylinders to match. u get weaker sleeves as a resault.

if you bore 0.25mm only it is still okay. otherwise honda wont come out with 81.25mm pistons. just my 2 cents

[spoondc2]

Since 81.25 is the limit of the stock block, so just make sure you check the wear if you really need to bore it, cos you won't be able to go back after you bore it 0.25mm more

Anyway, the good thing is, after you bore it and fit 81.25mm piston, it basiclly become a new condition block, since there are no wear between the ring and the wall so you won't burn oil like those high mileage vtec car do, and you will be able to gain some more compression ratio which gives you more torque

[TODA AU]

81.00 - stock bore
81.25 - 1st over size
81.50 - 2nd over size - works fine too
82.00 - recommend re-sleave but not 100% nessesary

Only bore & hone with dummy head in place...

[spoondc2]

But 81.50 seems too dangerous for stock block?

[TODA AU]

But 81.50 seems too dangerous for stock block?

For normally aspirated applications, there is no problem using 81.50mm pistons...
Correct & acurate machining is everything, if it's done correctly you'll have no problem.
FWIW, our B18 power'd civic runs 81.50mm pistons for now & we've had no problems at all with sleaves cracking etc...
Have it machined properly & steer clear of houso add-ons like posting & block guards & you'll have no problems...
In a turbocharged application I prefer to stick with 81.25mm as a limit, though I've had no problem with 81.50mm...
Hope that helps...
Cheers

Adrian

[**Ghost**]

how big a job is it to "bore' the cylinders? : ) thanks for teh rplies guys...

[blackdc2]

you have to remove the engine from the car... i guess it all depends on how much practice you have had at it

then you have to pull the whole engine down

then you have to send the block to a shop to machine it, then you have to re assemble the whole engine and put it back in your car.