The thermostat that came in my Riviera was a 195 and kept the stock car running fine. I added a cam, shorty headers, full exhaust, and converter, hopping up the performance and installing a 180 degree thermostat. I will soon be installing ported heads on the same shortblock with a B4B intake. I intend to use a 160 degree thermostat, as my dynamic compression is approaching 8:1. I will be running pump gas 93, and I am wondering if this is too cold for the engine.