I have an engine and it has a code just above the water pump that reads 3161 GM5.0L and I'm trying to find out what size the motor is.thanks preston

Probably a 307. A 5.7L is a 350.

A 5.0L is a late model (80's up) 305 V8. The 307 did not have any displacement stamped on it.

Thanks El. Ya learn something new everyday here!