changing piston rings

[bcjammerx]

Cool. Which is of course why you still need to pull the pistons out to measure the cylinders roundness to verify.

[johnl]

Cool. Which is of course why you still need to pull the pistons out to measure the cylinders roundness to verify.

At which point most people (including me) will opt to fit new rings and hone 'just in case'...

When I was racing karts (the good old days...), I'd fit a new piston and ring to a honed cylinder, then after a few race meetings I'd fit a new ring to the old piston without honing the cylinder. The engine always felt just a tad stronger on this second ring than it felt on the original ring...

[rexload]

Forged pistons are only useful if you actually need forged pistons. If you don't (and in most cases they are most likely not really needed, even with a significant increase in engine output), then they may actually be problematic.

Forged pistons are usually intended for racing applications and likely to be made from an alloy that has very different properties to the alloy in the OE pistons. They may require larger clearances that might cause noisy operation (piston 'slap') and possibly faster wear etc...

The OE pistons are very good, and unless you are very substantially increasing output and / or rpm then are probably the best bet for a road car. If you're trying to raise the CR significantly you may or may not be able to find factory pistons to do this, but if not then this doesn't necessarily mean that you need forged items if good aftermarket cast pistons are available....

Thank you for the detailed explanation. That is exactly the reason why forged pistons were mentioned - it would allow to increase the engine output to 400+hp.