If you're searching for information about the Cummins 4BT diesel engine and how it differs from the 6BT, you likely fall into one of three camps. Camp one enjoys reading about obscure diesel engines.
The Cummins 4BT might be a powerhouse ... but you'll run the risk of wearing out the stock parts quickly if you go much higher. No matter the case, the 6BT has a lot more power than the 4BT.