Simple Pig Latin Translator
This looks pretty decent for a beginner. Some suggestions:


Making a variable space instead of using the literal directly is actually a kind of nice idea. You can improve the code by marking the local const.
Why is pos an integer? it only has two values, and you are using it to test a condition. Use a bool instead.
For that matter, why have pos in the first place? Pos tells you the same thing as pig1.Length == 0.
Any time you write a comment, ask yourself did I add this comment because the code was unclear? and then can I write the code so clearly that I don't need the comment?  You say 

string pig2 = ""; // First letter


Dude. If the name of the variable is firstLetter then you don't need the comment.
pig2 is just one letter, so it can be a char instead of a string. You can say:

char firstLetter;
...
firstLetter = word[0];

You're using pig1 as an accumulator; you're accumulating the final result piece by piece. This is totally fine for small strings. If that string was really big then this is not an efficient technique; you should use StringBuilder instead if you want to make an accumulator for a large string.
Finally, like I said, this is fine for a beginner, walk before you run, and so on. To give you a sense of how an expert would write this code, I'd write it like this:

string pigLatin = string.Join(" ", 
  engword.Split()
         .Select(word =&gt; word.Substring(1, word.Length - 1) + word[0] + "ay"));


Which is nicely compact.