CB360 Piston Rings - What to do

[3DogNate]

Ok, so I'm about to tear down my 360 engine. I'm at least gonna replace the piston rings with standard rings. The motor ran when I got it, no smoke from the exhaust, so I assume that the cylinder walls are probably OK. Won't know for sure until I get it broken down. But assuming that the walls are okay and I'm going to replace the rings. Do I go ahead and have the cylinders bored over and step up the ring size, as a precautionary step to have a successful rebuild? Or just stick to standard sized rings?

I don't think that want to get into new pistons though. Unless going 376 really adds that much more oomph... (I'm not planning on racing BTW)

 

[Sonreir]

Going 378 does add oomph. A lot, actually. The intake port size on the 360 is generally considered to be too large and when you up the bore on the cylinders you get a bit of a double-whammy; increase displacement and increased intake velocity. I think one pf pj's motors pushing close to 40hp (17% increase in power) from just boring and higher compression.

If you decide against going that route, I would still advice taking the cylinders to a machinist. A new hone will really help new rings seat better (don't reuse old rings, if you can help it) but as the honing process does remove a bit of metal, it's possible that you can go out of spec from the hone.

 

[3DogNate]

Are a pair of GS850 pistons my only option for going 378? (aside from custom pistons, which I'm not willing to pay for if I'm not heading to the track.)

I'll need to decide in the next two weeks... what to do.... I'll plan for a standard ring set unless a pair of pistons fall in my lap.

Going 378 does add oomph. A lot, actually. The intake port size on the 360 is generally considered to be too large and when you up the bore on the cylinders you get a bit of a double-whammy; increase displacement and increased intake velocity. I think one pf pj's motors pushing close to 40hp (17% increase in power) from just boring and higher compression.

If you decide against going that route, I would still advice taking the cylinders to a machinist. A new hone will really help new rings seat better (don't reuse old rings, if you can help it) but as the honing process does remove a bit of metal, it's possible that you can go out of spec from the hone.

 

[duggyb]

i am also interested in wat stock pistons i can get that work as an overbore for 360s

 

[OJ]

GS850 pistons are the best way to go, if you can find some, as far as I know. XS400 pistons would fit as well, but compression won't be that high as the piston tops are pretty much flat. I have no idea if using just gasket maker as base gasket would help compression.