Dodge Durango Forum II

Everything you never wanted to know about crank shafts

You would be much better off spending your money on machine work. Stock cast cranks can be used in very high horsepower applications if some effort is put into magnafluxing, shot peening, straightening, indexing, and balancing them. Balancing is critically important. A one ounce imbalance, at the center of the rod journal can add 15 pounds of unwanted force to the crank at 6000 RPM. Some stock cranks have been found out of balance by 25 ounces. Tha's a whole lot of extra stress that's easy to eliminate. Stock crank journals are usually not as parallel as they should be so straightening is also important to relieve stress. You can also make sure the journals are perfectly round and the stroke is as advertised. Stock cranks rarely have full stroke and can be off by up to.050".

There's a bunch of things you can do to the rest of the bottom end to make it stronger too. It's easy to think that buying the best bolt on parts will build a great engine. Truth is, a competent machinist is worth far more than the finest forgings around. If you do decide to buy a forged crank, you should have the same machine work done to it to ensure that it's perfect. Granted, it'll probably be much better than stock out of the box but it should still be checked out.

Good luck,

Dave Roman

Sat Dec 2