Unless your buying this to look at, I wouldn't worry about the non-original engine at all. This car only came with 190hp if I remember right. Yugos can damn near beat this car. I find this totally unacceptable, thus the ZZ4 in my car. Given the shape (my visual only) of this car, I'd guess it is worth at most $11.5 or so. Depending on what has been done to the suspension and other components, it might be worth a tad more.

 

The thing is that while each individual buyer and seller can determine for themselves what adds or subtracts value, the market is a composite of ALL of those buyers and sellers, and the market says that originality (particularly of the engine) adds value. Some people pull the original and then keep it - that's fine too.

What many people forget - and what I think might be your point - is that the aftermarket parts have some level of value too. For some things that value might be much lower than the original parts, but if a 1975 Vette has a $20,000 engine in it, the resale value of that engine might exceed the resale value of the entire car with the original engine. So yes - having a non-original engine DOES reduce a car's value on the open market, but the NEW engine might well add more value than not having the original will take away.

You have to look at the whole thing.

But the best bet is to have the original engine stored safely away somewhere so you can have both the value of a numbers-matching car as well as the fun (and value) of a more powerful engine.

Someone is going to say that if numbers-matching doesn't matter to you then don't worry about it. I agree, except that I would add that if you don't want a numbers-matching car then you should take advantage of that and save a little money by paying less...