Engine Operating Temps

Steve Cassani · #1 (**permalink**) 10-20-2004, 09:06 AM

I have an SPF with a 351 Windsor stock block. The cooler temperatures in Montana have left me with a concern for the engines operating temperatures:

Ambient air Temp (F) Water Temp (C) Oil Temp (C)
85-90' 69-74' 66-68'
70-85' 64-68' 64-66'
50-70' 64-68' 55-62'

With ambient temps in the 70-85' range, a check of the hoses leading to and from the radiator indicates that the main hose leading to the top of the radiator is cool. The burden for circulating water through the cooling system is being carried by the half-inch bypass hose. At 85-90', the main hoses are warmer but still somewhat less than one would expect if the thermostat were fully open.

My diagnosis is that the radiator is cooling more efficiently than the engine is generating heat. This explains why the thermostat is not fully open even on the warmest days. In cooler weather, the thermostat is closed and the volume and rate of circulation provided by the by-pass hose is enough to maintain temperatures at the indicated levels. If I'm right, replacing the 160' (F) thermostat with a 180' (F) unit will not help to increase operating temperatures. The by-pass will continue to maintain flows at a minimal level and this rate cools the engine to the indicated temperatures.

Discussion with Dynamic rules out covering a portion of the radiator.

When caught in traffic, the water temps rise fairly quickly and the fans come on at an indicated 93' (C). The fans are adequate to maintain water temps at this level until I am traveling at a sustained 35-40mph. Then the water temps drop fairly quickly to the indicated range.

The oil cooler is not connected. As you see from the table, oil temps track with the indicated water temps. I'm using Mobil One 15-50.

I haven't experianced any problems with engine performance or drivability. I've been through three oil changes and the oil looks great. As you might expect, the car has to be on the road for 15-20 minutes, at 2,100 RPM, before the oil temp guage comes off the peg. Water temps are achieved in less than 3 minutes.