Whatfailed? the actual metal or the joints where it was fabricated, you don't say what the fabrication method was? Pinned, soldered, loctite, etc.

J

If an EN1a crank shaft failed in just a few minutes running then an EN8 one running under the same conditions won't last much longer . Find out why existing crankshaft failed – failure could be due to a multitude of causes .

Couldn't say without seeing bits but some common causes of early failures are :

Unsatisfactory design or manufacture .

Running engine without any load .

Lubrication failure .

Transitional or full seizure .

Ovrspeeding .

Swarf and debris .

Examine the failed crankshaft very carefully under a magnifying glass yourself or put some good pictures on here – there are likely to be many visible clues as to what actually happened .

Michael Williams .

Can you give us an idea of the stroke and bore of the engine as it may be your pins are just too small for the power going through the engine.

Also how many bearings are there on the crank shaft, if its an inline 4 and you only have support at the ends then its likely to be too whippy.

Are you certain that one of the solder joints has not failed and the pin rotated slightly in the web, I always like to pin my cranks after soldering.

J

sounds like you need to change the big end journals and use needle roller bearings of the right diameter, silver solder them to the webs and problem solved.

dean