Mercedes Benz repair: performance, design alterations, propane injection

Question
I have a 83 240d 67hp what is its top speed,without throwing a rod i rencently drove to panama city fl. but kept it around 65 or 70   and also what if anything can i do to increse performance besides keeping good maintainance. thank you. this model did not have a turbo.

Answer
Answer:
65-70 MPH.
There are three real  performance improvements (power boost) possible, without major engine engineering/design alterations:

#1.Remove the automatic transmission and replace it with a five speed manual (if you can find one).

#2. In theory you can add a turbo, but it will reduce engine life.

#3. Propane injection may add a slight boost, however you loose space and you must refill the tanks constantly.

Best advice:
Buy a different vehicle.

A 300SD can hold 100 MPH all day long and it has modern acceleration speed.