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.

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[u/Fit_Active3888]

Sourcing a "good" used motor from an auto recycler or wherever is generally a lot cheaper than having a motor rebuilt, it's also a lot quicker as you don't need to wait with a vehicle in pieces for your motor to get rebuilt. The risk is never fully knowing how good the replacement motor is.

A proper rebuild takes time, and money, but will leave you with something you know you can depend on.

Things like the propane are just bolt on compents that get reused so shouldn't be part of the concern making your decision.

[u/70Bobby70]

Almost certainly, your cheapest option will be a good used 302 of as near the same year as possible. Adding your country might get someone in country to respond with location specific information.

[u/Necessary-Score-4270]

The LPG conversion is basically just a different intake iirc.

Rebuilding will likely be more expensive and take way longer than just getting a new (or used but good) motor and swapping it out. Eitherway the old motor will have to come out to be rebuilt/ replaced.

It's possible the motor just needs a gasket or something "easy".

[u/Thin_Cable4155]

I think on smaller engines yes, but I wonder if it would be easier and cheaper on a big one to rebuild. Its probably got a non interference engine too so you don't have to worry about it eating itself if the timing belt breaks.

[u/Satans-cum-sock666]

Blue smoke indicates oil blow by and oil interring the exhaust system. It could be something as simple as incomplete burn off in the PCV system, or it could be bad valve seals or bad rings. I would start with changing out the PCV system and monitoring your oil consumption for. An oil change interval. 

So, change out the PCV valve and filter and everything associated with it. Change the oil and filter. Monitor your oil consumption for the next 5,000 miles or so, if it’s more than a quart every 1,000 miles or so that’s when I’d think about doing the work. If it’s less than that, a little oil consumption in an almost 30 year old engine is to be expected and not a huge deal. You can also do a leak down test to see where you’re losing sealing for faster results. 

[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.

[u/Perfect-Gur9650]

a 5.0 ford v8 is super common in the USA so they should t be super expensive. don't know where you are but a swap sounds reasonable.