If I go from a 4" stroke to a 4.125" storke do I have to change rod length or do I still use the stock length rod?

Thanks

Chad

 

Unless you want to throw your pistons through the heads, you would need a shorter rod length or smaller pistons.

Most builds I've seen still go with the 6.125 rod but get the appropriate piston size for thar rod and stroke combo.

 

If you swap to a 4.125" crank and you already have 6.125" rods, you can reuse them. You just have to swap your pistons. This is one reason why most 4.125" builds are strictly NA. Your piston is getting pretty thin at that level.