Breaking Con-rod Cap bolts.

[Coollhand]

My V6 235 is breaking bolts in the con-rods that hold the cap on the end and attach the con-rod to the crankshaft. The really strange thing is that the bolts appear to be breaking whilst the engine is being hand-turned and not whilst it is running. I am re-building the engine after it took a swim and have never previously had any problems with it. I am completely mystified as to why rotating the flywheel by hand appears to break the bolts. The bolts are all HT of course. The only possibility I can think of is that whilst re-***embling the engine I have rotated the flywheel in reverse and for some reason this has placed the bolts in great tension and they have snapped. Has anyone ever heard of this happening? I am of course concerned that their is something more fundamental wrong with the engine and that the bolts will snap whilt the engine is running and it will then be destroyed.

Lucas.

[boats.net]

This is an unusual issue. If the motor was previously rebuilt, the rod bolts are supposed to be replaced. If there was excessive tension you would notice when turning over by hand. Not sure what can be referred to.

[Coollhand]

Yeah - bit strange isn't it? I see just three possibilities here:
1) The bolts were orginally overtightened and broke because the engine sank and perhaps the jolt of it hitting the sea-bed was enough to snap them - pretty unlikely though,
2) The bolts snapped while engine was running and somehow the engine ran on five cylinders with four bits of bolts and a con-rop cap bouncing around inside it - almost unbelievable,
3) The bolts snapped for reasons I simply cannot explain after the engine was salvaged - possibly because it was rotated in reverse?

I cannot think of another possibility and the three above are quite hard to believe. At this stage I intend to simply replace the bolts and keep going.

[boats.net]

At this point I agree, replace and keep going, be sure to look for internal damage.