What company out there makes a Lightweight crank and rods for a LTx motor, is the LT4 crank and rods lighter then the the LT1?

 

The LT4 rods are the same as the LT1. The crank is the same material but has larger, undercut fillet radii. This makes it stronger, not lighter. Cranks and rods designated as "lightweight" are usually very high end racing pieces. They are not as strong as equal quality "standard weight" pieces, though they may be much stronger than low quality, heavy pieces. In general, stay away from parts designated as "lightweight" unless you are building a max effort motor that will have a rigorous maintainence/teardown regime. In all cases, boosted and nitrous motors should not use them.

Rich