What year car?
630xxxx decodes two ways, either a 1970 S engine, or a 1980 SC ROW. The engine type number will tell which is which. The 1970 S will have a type number of 911/02, the 1980 engine will have a type number of 930/09.
Here's a link to a good source, but it's in German. Easily understood, however.
Porsche 911 SC - Modell 1978-1983
The S engine is 180hp at 6800rpm. The SC ROW engine is 188hp at 5500rpm.