ZR-1 Net Registry Forums - View Single Post - Cooler Thermostats, Thermostat Modifications and Engine RPM

Dynomite · 11-29-2018

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Cooler Thermostats, Thermostat Modifications, Engine RPM, and Fans

Here is what I have found regarding LT5 Stant Thermostats.

1. You want to run the engine at coolant Temperatures of 180 deg as the design requirement...……...Running cooler Thermostats only lowers coolant temperatures when running coolant below 180 deg F (which is too cold for the LT5 engine). Once the 180 deg Thermostat and 160 deg Thermostat are fully open at 180 deg, Coolant flow is the same through each Thermostat with equal cooling as directly dependent on coolant flow.
2. Drilling Holes in Thermostats offers minimal (non effective) additional Coolant Flow...….A 1/8 inch diameter hole in the flange will only offer additional flow area of .0123 square inches. Which one such hole will increase the total flow area by .016 or 1.6% (three 1/8 inch diameter holes would increase the flow area by 4.7%). This thinking does not address the change in coefficient of Discharge of such small holes. The Stants tested would be fully open with a flow area of approximately .785 square inches at 185 deg F.
3. The Stant Thermostat Opens a bit less with age......…...Marc suggests a 15% deterioration in Full opening area of the Thermostat over time as the Thermostat ages.
4. The LT5 Water Pump Flow is proportional to Engine RPM. ......The LT5 Water Pump Flow rate is insufficient at RPMs less than 2,000 RPM for adequate Coolant flow at the higher Ambient Temperatures. Larger Aluminum Radiators DO compensate for inadequate Coolant Flow at low RPMs. Fans Turning on at 205 deg F do help considerably. And KEEP The Radiator, Oil Cooler, AC Condenser CLEAN.
5. Fan Air Flow is inadequate when the ZR-1 is not moving...…..This was noticed when the ZR-1 coolant decreased in Temperature when shifting from 6th to 5th at 65 mph (going from 1,500 to 2,200 rpm) but while not moving increasing the rpm from 750 to 2,000 had the opposite effect actually increasing coolant temperature.

And I was thinking the issue was solved wherein it is TWO issues (Fan air flow at low speeds and water pump coolant flow at low rpms).

In regard to Item #2 and #3 above...…..Compared to the normal aging of the thermostat of 15% over several years of use one would be much better off installing a NEW Stant Thermostat gaining 15% flow area as compared to drilling three 1/8 inch holes in an older Stant Thermostat only gaining 4.7% flow area.

See Post 120 - Thermostats, Fans, Radiators and Coolant Filling

Post 286 - Cooler Thermostats, Thermostat Modifications, Engine RPM, and Fans

11-29-2018	#1
Dynomite Join Date: Aug 2009 Location: South Dakota/California Posts: 3,788	Cooler Thermostats, Thermostat Modifications, Engine RPM, and Fans Debate This Cooler Thermostats, Thermostat Modifications, Engine RPM, and Fans Here is what I have found regarding LT5 Stant Thermostats. 1. You want to run the engine at coolant Temperatures of 180 deg as the design requirement...……...Running cooler Thermostats only lowers coolant temperatures when running coolant below 180 deg F (which is too cold for the LT5 engine). Once the 180 deg Thermostat and 160 deg Thermostat are fully open at 180 deg, Coolant flow is the same through each Thermostat with equal cooling as directly dependent on coolant flow. 2. Drilling Holes in Thermostats offers minimal (non effective) additional Coolant Flow...….A 1/8 inch diameter hole in the flange will only offer additional flow area of .0123 square inches. Which one such hole will increase the total flow area by .016 or 1.6% (three 1/8 inch diameter holes would increase the flow area by 4.7%). This thinking does not address the change in coefficient of Discharge of such small holes. The Stants tested would be fully open with a flow area of approximately .785 square inches at 185 deg F. 3. The Stant Thermostat Opens a bit less with age......…...Marc suggests a 15% deterioration in Full opening area of the Thermostat over time as the Thermostat ages. 4. The LT5 Water Pump Flow is proportional to Engine RPM. ......The LT5 Water Pump Flow rate is insufficient at RPMs less than 2,000 RPM for adequate Coolant flow at the higher Ambient Temperatures. Larger Aluminum Radiators DO compensate for inadequate Coolant Flow at low RPMs. Fans Turning on at 205 deg F do help considerably. And KEEP The Radiator, Oil Cooler, AC Condenser CLEAN. 5. Fan Air Flow is inadequate when the ZR-1 is not moving...…..This was noticed when the ZR-1 coolant decreased in Temperature when shifting from 6th to 5th at 65 mph (going from 1,500 to 2,200 rpm) but while not moving increasing the rpm from 750 to 2,000 had the opposite effect actually increasing coolant temperature. And I was thinking the issue was solved wherein it is TWO issues (Fan air flow at low speeds and water pump coolant flow at low rpms). In regard to Item #2 and #3 above...…..Compared to the normal aging of the thermostat of 15% over several years of use one would be much better off installing a NEW Stant Thermostat gaining 15% flow area as compared to drilling three 1/8 inch holes in an older Stant Thermostat only gaining 4.7% flow area. See Post 120 - Thermostats, Fans, Radiators and Coolant Filling Post 286 - Cooler Thermostats, Thermostat Modifications, Engine RPM, and Fans __________________ Left Clickable links -Solutions- LT5 Modifications/Rebuild Tricks Low Mileage ZR-1 Restoration 1990 Corvette (L98) Modifications LT5 Eliminated Systems LT5 Added Systems LT5/ZR-1 Fluids 1995 LT5 SPECIFIC TOP END REBUILD TRICKS Last edited by Dynomite; 12-11-2018 at 10:57 AM.