Good evening friend, greetings from Zulia State; well, first of all, it is always advisable and advisable to adhere and respect the design of the equipment, in your case, you have a small refrigerator that uses 1/6 engine and another with 1/3 engine, the difference between the grills is that, the 1/3 engine cooling system is much larger than the 1/6 system, therefore, both evaporators and condensers will be larger in the case of 1/3 engines, and as these engines have a capacity refrigerator of around 1000 btu / h, compared to 1/6 engines whose capacity is around 580 btu / h, we are talking about that 1/3 engines extract almost twice the heat of what 1 / 6, therefore, it will require that the condensing grill, in charge of subcooling the refrigerant gas that leaves the compressor, be wider, if you put a 1/6 grill to a 1/3 engine, it will end up burning the compressor by overheating ; On the other hand, I think that those engines that are worth 100 dollars are new, here in Venezuela, there are imported compressors of very high quality and very well preserved, of different brands (Embraco, LG, Matsushita, Tecumseh, etc.), and they are working very well I don't know where you are from, but here in Zulia State there are importers where they sell them used for around $ 30, in my case, I always recommend the customer to buy imported, for 2 factors, the first the price, and the second is that I consider that the imported units are much better than the new ones they are selling, with rare brands and many of them do not reach 2 years of use, but of course, it would be your decision; in relation to changing everything (evaporator and condenser) for the small refrigerator, you will have the inconvenience, first of all that it fits you and looks good, and secondly that the interior space of the small refrigerator may not have enough load thermal as to evaporate all the liquid refrigerant from the evaporator, therefore, you could have problems returning liquid refrigerant to the compressor and it would end up being damaged, of course, at first it will give the impression that it cools a barbarity, but you will have to properly calibrate the amount of refrigerant so that you do not return liquid, for these things, I think it is best that you invest in a unit of 1/6 for your small refrigerator, refrigeration inventions usually give many headaches for both the technician and the customer, and in the end, the cost will be much higher.