County Pistons and Rings

[Norman D]

Have reached engine rebuilding stage and have bought pistons and liners from Moss, County is the manufacturer, the liners have been fitted and deck height is 4thou for each liner, well done whoever machined these! My query is about the piston rings which were packed seperately, the middle rings no 2 if you prefer, have a step in them, have they been wrongly labelled as I have only seen a step in the top rings previously and then only when fitting new rings to old bores? If they are to go in the middle why do they need a step and which way up do they go? Thanks in advance for any help offered. Norman.

[Rhodri]

Instructions that came with my County pistons, seperate rings, from Moss - 87mm

 

Rod

[marko]

The stepped Top Ring would be fitted with the step upwards, it's known as a ridge dodger. This is to avoid contact with the lip at the top of the bore caused by wear & tear of the piston rings running in the bore. If there is no step on the piston ring it can be fitted either way up.

 

A stepped middle ring should be fitted with the step facing downwards this is to aid the oil scraper ring (3rd ring) stopping excess oil reaching the top of the piston.

 

Don't forget County Piston Rings must be gapped with a 2-3 thou gap per inch of bore.

 

Here endeth the lesson for today...........

[Norman D]

Thanks for fast response Marko and Rhodri, using a watchmakers lupe(magnifying eyepiece) I can now see the word TOP ont the middle ring and the cutaway does indeed face downwards. The ring gaps are spot on too.Hurray