Liner top oscillations

[wayneschofield]

Has anyone noticed these marks on the head before? .... Of course you have but has anyone thought to look what causes them?

When I first saw them I just figured they were a result of some uneven cooling, since the marks are around the area of the waterways so I didn't pay them much attention but, looking at it under the microscope, you can clearly see that the marks are caused by the liners 'swelling' under pressure, with the areas near to the head bolts staying put and the rest of the liner is moving in and out.

I know the liners sometimes split but I just figured that it was down to the drilling being too deep but, thinking about it some more, it's likely that fatigue is causing it and the drilling just accelerates the failure.

The fact is, if the bores are swelling, they aren't round when the cylinder pressure is most needing to be kept in the cylinder. The rings won't assume a semi-square shape very readily and they certainly won't 'follow' a moving bore.

Anyways, I reckon we need liners with a much larger flange at the top, preferably right out to the outer case diameter, then the case can help support the liner. Of course we will need four slots machined in them for the coolant to pass but that's all.

With that much more support, and perhaps the bottom of the case counterbore opened up some too, we could perhaps go to 100mm bore which, with 63.4mm stroke, would give 498cc - ideal for a 500 class motor.

[cannondale27]

Everything is moving around in our motors.Same type thing goes on between crankplate and case even with tight bolts.Alot of it could be from thermal movement.