1979 280zx piston in 1978 L20b

[maredlin1@hotmail.com]

I have looked for what the ring gap for the top ring, second ring and oil rings (which seem to be a secret) are in real feeler gauge terms. I get replays like .0098-.0157. Ether I need a better set of gauges or I no comprehendo. I have a nice ring filler, but would like to know what would be perfect set them at. Like top ring .010 second ring .020 and oil rings at ?

Thanks for any information

[datzenmike]

For a stock use hyper-eutectic piston about 0.004" per inch of bore. On an 86mm bore that's 3.388" X 0.004" = 0.0135 gap for the top ring.

 

Second ring is about 0.005" per inch.

 

This is not exact but a general rule.

[maredlin1@hotmail.com]

Plus the tolerance cannot be the same as a stock 280zx, because I have cut about half of the cylinder wall off.

[maredlin1@hotmail.com]

Do the oil rings get gaped?

[Laecaon]

OIl rings dont get gapped.

[MicroMachinery]

OIl rings get staggered.

[scooter]

Cut half the cylinder wall off? Cylinder wall thickness has not alot to do with end gap. For stockish applications (stock280zx pistons) you can use the book tolerances. If your gonna hammer the shit out if it, you can increase the gap a little, but dont go over the service limit, just to the higher end of the spec. Too much gap doesnt do anything but lose horsepower and cause blowby.

[datzenmike]

Plus the tolerance cannot be the same as a stock 280zx, because I have cut about half of the cylinder wall off.

 

Sure it can. If you had an 85mm bore L20B and you over size it to 86mm to fit other pistons you would gap according to the new diameter. It won't be much of a change though, in fact not even worth worrying about. You could still use the ring gap for the L20B it's that close.