Join Date: Jul 2006
Location: Northfield, Illinois
As I explained to you in an e-mail, this CAN happen. Often there is no "fault" to be found. I'm writing this for others, Wes, that might not understand. The most common cause is always detonation. This can be from any number of other causes, but often comes from failure to re-calculate CC volume AFTER a bore increase. Compression WILL increase.
Assuming calculations are correct, and piston crowns have been cut enough to get compression back where it should be, and assembly is correct, we are down to simply "liner-failure".
Many quality new liners are "spun-cast" in an attempt to minimize stresses in the actual casting.
These new liners are often honed to final dimension and finish rather than bored with a boring bar.
Used liners, made up for oversize bores, should also be honed to size with a Sunnin honing machine or the like. This machine is commonly used for aircraft liners and cylinders, as well as cylinders in motorcycles, and other "dry" liners. The purpose is to minimize any stresses built up in the casting. If a boring bar is used, even with a sharp cutter, some slight metal is displaced rather than cut, due to the nature of most castings. This creates stresses in the liner, and with heat / cool cycles, the stresses will be relieved to some extent, BUT one relief is a stress crack, and that's never good.
Honed liners may also have stresses, but not caused by the honing, though they may be brought to the surface by honing.
I prefer USED liners for all overbore applications as the hot/cold cycles hopefully have negated some stresses from manufacture. These are used in my own 1600's with a 79 mm bore. Liner skirts get pretty thin at 80mm, and boring the block for cut down 1750 liners may weaken the block itself. With the 1600 block, you can go big, but form building "BIG" small bore motorcycle engines, blocks may get pretty jello-like. You can discuss this with Jim Steck, who has built some pretty powerful Alfa engines for Bonneville. These blocks are seriously reinforced both top with mono-liner, and bottom with steel cradle, to avoid the jello issues.
Cracked liners are annoying, and can and do happen. Compression, machining, assembly, and unknown existing liner stresses all can contribute.
The above is from my own experiences, as well as of others I know well. I hope it is useful information.
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