They can last awhile if not beat on, but they are neither powerhouses nor fuel sippers, just cheap to make. If the OP wants to make his car faster, a powertrain swap is the only worthwhile option. Trying to do anything other than upkeep to a 231 is a waste of money. The issues with making power with a 231 are low compression ratio, restrictive heads, lack of performance parts for the N/A versions, highly restrictive exhaust manifolds, and being a 90 degree V6. After those, you have the weak TH200 with no OD, restrictive single exhaust, lame 2.41 rear gear ratio, and weak V6 suspension springs.
It is wishful thinking of the OP to think emission or computer deletes will improve his car's performance at all as they won't. Such deletes will only worsen his MPGs and waste money and time. The true problems preventing performance improvrment are all major ones that are easist to fix by a powertrain swap. The OP should keep his car stock and if he wants to go faster then he will need to start saving up for a powertrain swap. However, the OP can work on improving his suspension, brakes, and body repair and reinforcement now to get the car ready for a swap later on. To go faster with a V6 car, you will need to add either a turbo, two extra cylinders, or even both.
he's satisfied with the engine and that is nice to hear that someone is happy with what he has.... 🙂
Cool any suggestions on a non ccc carb that would be good for 231? I'm not looking for power just want a reliable everyday cruiser