Personal experience with the engines i work on- 160 for boosted, 170 N/A. Now those are engines that see almost exclusively track time (road course), for a street engine I would bump it up 5 to 10 degrees from there, depending on use/driving style/planned track days, etc. Better question, what are your engine specs/what has been done to your engine (how much heat are you creating)? Stock/mild cam- go 180 and call it a day. Big bore/big cam/high compression/destroked 8000 RPM screamer- go 170-175. Running 15 psi through a top mount supercharger on pump gas- ~165ish.