Q

I restored/rebuilt my 1934 Dodge pickup for the last time last year. The engine is a 327 SBC with flat-top pistons, a 350hp/350ci cam, 2.02/1.60 heads, an Edelbrock EPS Performer manifold with a 570-cfm Holley, Sanderson QP-1000 ceramic-coated headers, 2-1/2 inch exhaust pipes, and ACCEL HEI. I have a Walker radiator.

The cooling system worked very well. Rarely did the temp rise above 160 degrees unless I was in stop-and-go traffic, then it might rise to about 180 degrees but then I had a cooling problem at Hot August Nights last year. With the constant sitting in traffic during the parades and very little movement, the temperature gauge rose to 240 degrees and above. I was constantly putting the AT in neutral and raising the rpm in an attempt to get the temp down.

I decided to change the system and go to an electric fan. I’ve been told to install a 180-degree high-flow thermostat with a 205-on/195-off temperature sensor; other sources say a carbureted engine should use a 160-degree thermostat with a 176-on/161-off sensor and a fuel-injected engine should use a 180 thermostat with a 200-on/185-off sensor. I can find sensors that are 185 degrees–on/165-off and 195-on/175-off, but it doesn’t say which thermostat to use. Another catalog lists sensors that are 185 degrees–on/170-off for a 180-degree thermostat and 200 degrees–on/185-off for a 195-degree thermostat.

Can you shed any light on my problem? Thanks.

If a street rod is equipped with a late-model, computer-controlled, fuel-injected engine, trying to run it too cold creates more ...

Charlie Beck
Fairfield, CA

A

Let’s start with engine-operating temperature first. Most engines today are designed to operate within a “normal” temperature range of 195 to 220 degrees. Of course one of the reasons for that can be traced to emission control regulations and equipment. But thanks to vastly improved lubricants and engine components these increased operating temperatures aren’t an issue.

If a street rod is equipped with a late-model, computer-controlled, fuel-injected engine, trying to run it too cold creates more problems than it cures—keep the engine in the 195-degree and slightly above range. On the other hand, older, carbureted engines can run a little cooler, with 180 degrees the goal.

As for thermostats, using one that opens at 160 degrees is thought by some to prevent overheating because it provides a temperature “buffer” of sorts—but it doesn’t, it just provides a lower starting point. If an engine is going to go to 240 degrees for whatever reason, it’s going to get that hot regardless of the thermostat. Thermostats establish minimum operating temperature, and unless one sticks closed or is for some reason more restrictive than normal, maximum water temperature is dependent on the remainder of the cooling system. When compared to a 160-degree thermostat, a 180 will provide cleaner combustion, warm the oil to the point that contaminates will “boil off” and in general performance will be improved. We always recommend the use of a high-flow thermostat that can be ordered from a number of our advertisers.

Another factor to consider is coolant. A 50/50 mixture of water and ethylene glycol antifreeze in the cooling system will boil at 225 degrees if the cap is open. But as long as the system is sealed and holds pressure, a radiator cap rated at 15 psi will increase the boiling temperature of a 50/50 coolant blend up to 265 degrees F. That’s not to say you want an engine to run that hot, but preventing the cooling system from losing fluid is essential to maintain the proper level.

As for electric fan controls the hot ticket (no pun intended) is for the “off” temperature to be slightly higher than the thermostat. Any lower than that and the thermostat may cycle open and closed and engine temperature will not stabilize, which presents its own set of problems. The “on” temperature of the switch is usually around 12 to 15 degrees above the “off” temperature.

Of course another option is one of the adjustable fan switches on the market; they allow you to tailor the set points for your particular application and maybe even more importantly, allow changes to be made easily whenever necessary.

Ron Ceridono