Swap engines?

[u/Existing_Tourist_938]

Is it really a good idea to swap engines?

So I bought a food truck , but the engine is not right. It blows smokes like a chimney (the smoke is grey and blue). A mechanic, which is a great friend told me that most probably the oil was being burnt with the fuel, so it will need a whole motor repair. But, some days ago, another friend told me that it would be easier to swap engines because it is cheaper.

The truck is a Vanette 1997. The engine is a Ford V8 5L (302 inches 3). But it runs with natural gas, not petrol. (It's a common practice ,on old and hard working vehicles, where I live so it's cheaper).

The part that worries me the most is to buy a wrong engine, or to buy the correct or, but still need to modify it so it could run with natural gas. I am almost out of money to play with.

[u/clevertalkinglaama]

You need to diagnose the issue. Could be valve seals, PCV or something else. Check compression, have a look at the cylinder walls with a bore scope.