Replace just one ring
 

I'm part way through my replacement of broken studs on my 911sc 204bhp model, and have removed the cylinders with pistons still inside - wasn't sure if Nikasil or Alusil at the time so didn't want to disturb them too much. I have since found out they are Nikasil :)

One of the pistons came out of the cylinder, so while it was out, I checked the rings and they are within tollerance, so I was planing not to seperate the other five. All cylinders look good. Here is my first big mistake ! Using a cheap :mad: ring compressor i managed to break the lower ring. I have a new set on order, but will I be ok replacing just the rings on this piston an leaving the other five as they are ?

Would I be best replacing all the rings on this piston, or just the broken one ?

Thanks

The oil ring is the most fragile and even the most careful builder will break one if they lose focus for a moment.

How old are the rings? If they are already broken in, I would replace them all, plus you are this far into disassembly, why not replace them all?

They have done around 75,000 miles, original rings.

So replace them all on the one cylinder.

You have nikasil cylinders and have the engine apart. Why not replace all the rings?

To the extent that you have a better seal on one cylinder than the others, this will just be confusing

I'll give the contrary advice. I'd just replace the broken oil ring. 75000 miles is nothing for Nickasil pistons and cylinders and rings. The brand new rings that you can buy usually have bigger end gaps than your old rings (like being worn out already). The old rings are broken in. There is always a chance of problems with new rings.

-Andy

Westy, did you replace just the broken ring or all three rings? How did it work out?

Went for just the one ring, all back together, except for injection and clutch change. Fingers crossed it was the right decission.

Thanks, and good luck down the home stretch.