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</o:shapelayout></xml><![endif]--></head><body lang=EN-GB link="#0563C1" vlink="#954F72" style='word-wrap:break-word'><div class=WordSection1><p class=MsoNormal>In a recent engine rebuild of a standard BJ7 engine which was fitted with four ring pistons, when I looked at replacement pistons they were pictured with five rings, which did not seem good to me.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I fitted Omega pistons from Denis Welch. These have three rings with a total width of 3.2mm compared with 9.8mm for the four rings. (For the oil rings only the width contacting the cylinder bore is measured)<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Since friction is in proportion to ring width (possibly due to the lower pressure required to make thinner rings seat against the cylinder wall) this represents a reduction in losses to heat and a power increase (small).<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Another, much more expensive, option for consideration. I also have no doubts about the quality of the pistons, whereas I am not sure about the four or five ringed replacements. They seem very cheap to me.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Ian<o:p></o:p></p></div></body></html>