Marks on cylinder walls

[abit]

Hi there, started to build m2b28 stroker and disassembled my current engine, maybe someone can tell what caused and is it bad, that my block cylinder walls has those strange bronze coloured marks from top compression rings I suppose? Honing marks are still pretty good though.

[mpowerful]

Is there a lip at the top?

[abit]

Is there a lip at the top?

No, all cylinders look pretty good. Actually can't even feel the lip with finger.

[jlevie]

I suspect those are discoloration from hot combustion gases.

[abit]

I suspect those are discoloration from hot combustion gases.

How bad it is? :-D or it will be OK?

[Cabriolet]

Get the block honed. If they are still there then I would worry.

[spdracrm3]

all normal marks notice the relation to the headbolt holes (this is a great example of how blocks distort due to the tension of the headbolts, not a perfectly round hole anymore) these are wears marks from the piston rings on the high spots caused by the distortion, which is why on racing engines they are bored/honed with a torque plate to eliminate distortion in the bores.

[jlevie]

How bad it is? :-D or it will be OK?

That is normal and to be expected.

[abit]

ok, thanks :)

[TobyB]

Having said that, this is why you measure. The shiny spots where the rings stop can
wear pretty significantly after several hundred thousand miles- the bores can be
really good, but there can be a 3-4 thou pocket right at the top. And that can disrupt
ring seal no end.

A machine shop hone will make it obvious if it's bad or go away if it's cosmetic.

You can also measure it with an inside mic. Or even those cheap inside snap gauges.

t

[jlevie]

Having said that, this is why you measure. The shiny spots where the rings stop can
wear pretty significantly after several hundred thousand miles- the bores can be
really good, but there can be a 3-4 thou pocket right at the top. And that can disrupt
ring seal no end.

A machine shop hone will make it obvious if it's bad or go away if it's cosmetic.

You can also measure it with an inside mic. Or even those cheap inside snap gauges.

t

This is true, but in my experience the wear will show up first at the lower end of the bores. The preferred measuring instrument is a dial or digital bore gauge that will read to a tenth. But of course you can only measure all the way down the bores if rebuilding the block.

[TobyB]

wear will show up first at the lower end of the bores.

Agreed, often. Where the skirts rock at BDC.
But on several high- mileage engines, I've found that there really is a
pocket that totals 3-4 thou right where the rings stop. It makes sense, I guess-
at dwell, the combustion pressures are building, the rings are being pressed harder and
harder against the bore, and there's relatively little movement.

Some are fine, some show it significantly. Easy to measure, expensive to fix.

t