Keeping her cool

[fixed66]

Hey all,

I have Superformance cobra, bondurnant edition, 427FE.... just had engine completely rebuilt a few years ago by an FE builder. After getting it back engine was running hot, thought it might be break in period but finally found radiator had huge blockage. Installed new radiator. In the process of diagnosing the “hot” temps, I took out the thermostat. Wondering do I need to/ or should I put it back in? She still loves to run hot, especially anytime it’s over 85 degrees here (live on Florida). Wondering should I just leave thermostat out or put it back in to help regulated water temp?

[cycleguy55]

The thermostat sets the minimum operating temperature, while the cooling system capacity sets the maximum. Leaving the thermostat out means your engine could run too cool - contributing to increased engine wear (yes, there's research to support that) and, arguably, oil never getting hot enough to drive moisture out.

If you're at all concerned, get a high flow thermostat. That's what I have - 180°F.

[Michael C Henry]

The old original FE has a Large diameter thermostat but it has a small valve, I found a Chrysler product thermostat that had the large diameter thermostat with a large valve. They make all sorts of thermostats that will ,if when they go bad will, be open position and so on. How is the temps front to back? The head gaskets have a passage for coolant from head to block. The passage goes to the rear and the front is blocked The coolant goes in the front of the block where the coolant pump is mounted then flows to the rear around the cylinders . at the rear of the block it flows up through the heads then flowing through the heads forward. then the manifold cross over to the thermostat. If you get the head gaskets mounted wrong that doesn't work. Make sure the thermostat by pass hose between the top of the coolant pump and the manifold is open. I have seen that short hose being blocked by an internal blister.

[bobcowan]

You need either a thermostat, or a restriction plate. If you leave those out, the water moves too quickly through the system and doesn't transfer heat. The water temperature will look good, but the heads will overheat. And that's a bad thing.

If your fuel mixture is too lean, or the timing is incorrect, it will run hot.

[ERA 626]

what about drilling a small hole in the thermostat to act as a bypass?

[cycleguy55]

Originally Posted by ERA 626

what about drilling a small hole in the thermostat to act as a bypass?

My thermostat has a 'jiggle pin' that allows air to flow through, then closes once coolant starts to flow.

[fixed66]

Thanks everyone, looks like the consensus is to re install the thermostat. Really appreciate the insight and guidance. I like the idea of a larger valve to increase water flow to allow engine to cool, but I don’t want to worry about waiting for the engine to warm up correctly before driving it. Thanks again. Love this forum.

[fixed66]

Thanks everyone, looks like the consensus is to re install the thermostat. Really appreciate the insight and guidance. I like the idea of a larger valve to increase water flow to allow engine to cool, but I don’t want to worry about waiting for the engine to warm up correctly before driving it. Thanks again. Love this forum.

[t walgamuth]

The engine was designed to have a thermostat. It will work best with that installed.

[strictlypersonl]

If you don't have a heater or heater bypass...

Thermostat modifications

[Tommy]

Originally Posted by bobcowan

You need either a thermostat, or a restriction plate. If you leave those out, the water moves too quickly through the system and doesn't transfer heat. The water temperature will look good, but the heads will overheat. And that's a bad thing.

This is a very common opinion, but incorrect based on my understanding of fluid dynamics and thermodynamics. Here is a more authoritative source: Flow Kooler

[bobcowan]

Originally Posted by Tommy

This is a very common opinion, but incorrect based on my understanding of fluid dynamics and thermodynamics. Here is a more authoritative source: Flow Kooler

That's a pretty interesting article. I know it works, because I've tried it. Detonation without the restriction. Smoother running and no detonation with it. But It looks like I didn't really understand why it worked.

[scootter]

I have a 514 in my Superformance. Mine runs cool all the time no matter the outside temps. It use to get a bit hotter. I found out the factory fan sensor in the radiator is a 195. To high. I replaced the radiator fan sensor to a 165, a 165 high flow thermostat. I did recently replace the radiator since mine is an 2002 with 55k miles. I had 5 or 6 tubes leaking. The radiator shop would not repair the aluminum radiator, so I had to order another one from Superformance $$$$$. It looks like the new one has one or 2 more rows!!
Scott

[cycleguy55]

Originally Posted by scootter

I have a 514 in my Superformance. Mine runs cool all the time no matter the outside temps. It use to get a bit hotter. I found out the factory fan sensor in the radiator is a 195. To high. I replaced the radiator fan sensor to a 165, a 165 high flow thermostat. I did recently replace the radiator since mine is an 2002 with 55k miles. I had 5 or 6 tubes leaking. The radiator shop would not repair the aluminum radiator, so I had to order another one from Superformance $$$$$. It looks like the new one has one or 2 more rows!!
Scott

What are your oil temperatures with the 165°F thermostat?

[scootter]

Originally Posted by cycleguy55

What are your oil temperatures with the 165°F thermostat?

Honestly I don't pay much attention to that one... I mainly look at the oil pressure, water temp and fuel gauge.
I would say in the 90 to 100 range. My oil cooler is not hooked up.

[cycleguy55]

Originally Posted by scootter

Honestly I don't pay much attention to that one... I mainly look at the oil pressure, water temp and fuel gauge.
I would say in the 90 to 100 range. My oil cooler is not hooked up.

"90 to 100 range"? I trust that's °C, meaning 194-212°F. That's okay, though not great.

Regardless, I believe a 165°F thermostat means your engine runs too cool. While that may be better for power, it increases engine wear - though most of us will never drive our cars enough that such wear becomes a significant factor.

Operating temperature vs power and longevity: HOTRODSRJ’s COOLING TIPS Operating temperature vs power and longevity!

[Timinator]

Oil temperature should be up around 190 or so. It works best at that temperature. You should strive to dial in your system so it heats to that after driving for 15 minutes or so and can stay around that temp for the duration. This is usually accomplished by a thermostatic valve and oil coolers.