Why not just remove thermostat?

[Bob Eyres]

#9 is the most relevant here Paul.

I don't know for sure, but I think an LT5 without a thermostat would blow the plastic components of the stock radiator apart.

[Paul Workman]

Originally Posted by Bob Eyres

#9 is the most relevant here Paul.

I don't know for sure, but I think an LT5 without a thermostat would blow the plastic components of the stock radiator apart.

Ah, YES. I wrote about those plastic tanks, but musta inadvertently deleted that point when I edited. Good catch!

[Dynomite]

Originally Posted by Paul Workman

Well, for starters:

1. Engines are expected to become hot.
2. Parts are expected to expand.
3. Parts work together best within certain tolerances.
4. Heat is controlled to keep parts tolerances in the range to assure longevity.
5. Lubricants are designed to specification that they meet certain characteristics over a range of certain temperatures.
6. Fuel (gasoline) must be completely vaporized to mix with oxygen before it will burn. (liquid gasoline droplets will only burn at the surface where oxygen is present)
7. Operating the LT5 (or any) motor at WOT below a certain minimum temp can result in damage (refer to #s 2, 3 & 5)
8. Operating (any) motor where gasoline is not being vaporized completely results in carbon buildup in combustion chambers and on valves, washing the cylinder walls of needed oil, and reducing the viscosity of the oil resulting in accelerated wear of cylinder walls, bearings, and rings.
   
9. And, last, but every bit as important, in the case of the LT5, certain steps are taken in the thermostat housing (with the thermostat in place) to control coolant over-pressurization resulting from high rpm operation.

These LT5s are a magnificent engineering achievement. They are kinda rare, parts are expensive, and provide a rare experience not felt in any other Corvettes before or since. And, when operating within their "window" they are nearly "bullet proof". If you operate this or any motor outside the design window, as some always will, you're "off the chart", and serendipity becomes your tutor. (But, NOT on my dime!)

Why not just remove thermostat? NO...NO...NO!!!!

I run 180 deg thermostats in ALL ZR-1s.

1. At a coolant temperature of say 190 deg a 160 deg thermostat is open....so is my 180 deg thermostat. So from that point on our coolant system flow rates are identical at the same rpm. And so is the cooling.

2. Using a 160 deg thermostat in cooler weather drops the engine coolant temperature below the designed engine temperature with the 180 deg thermostat. The PVC (at the cooler engine temperatures) is working at less than optimum temperatures as well as your oil and fuel functioning at less than optimum temperatures.

Also see Defective Stant Thermostats

Oh....almost forgot.....my fans come on a bit sooner controlled by Marc Haibeck chip to help with engine temperatures when idling at a traffic light on a hot day (On at 205 deg F and Off at 200 deg F). But again....my 180 deg thermostat and the 160 deg thermostat are both open in that condition

But MUCH MORE as you can see as the LT5 thermostat has several functions LT5 Thermostats

2. Thermostat Multiple Functions.

The LT5 thermostat sits in two cavities and is located on the outlet side of the radiator. On one end of the thermostat is the first valve [pressure relief) that expands and opens to excessive radiator pressure (but only relative pressure over and above that normal thermal expansion radiator pressure). That valve is in the first cavity which is exposed to coolant outlet flow. In the second cavity is the second thermostat valve (temperature relief) which controls coolant inlet flow depending on engine temperature.

GM found at high rpm and high coolant flow, excessive pressure in the radiator, due to it's restriction, would blow the rubber seals between the side tanks and the core. GM did not want to design a specific LT5 radiator, so the solution was the radiator bypass which opens when the pressure differential across the radiator reaches a certain level. This bypass valve is part of the thermostat and, when open, allows coolant to recirculate within the engine.
LT5 Coolant System Discussion

ZR1 provided this photo in the LT5 Coolant System Discussion :thumbs:



3. Lets simplify......the discussion of the 160 deg thermostat cooling better than the 180 deg thermostat.

1. Let us say we have identical radiators, identical rpm, steady state coolant temperature, and both fans on and we are cruising at same speed.
2. Lets say coolant temperature is 190 deg in both your Z and my Z given everything identical in item #1.
3. Your 160 deg thermostat is full open with same flow rate as fully open 180 deg thermostat.
4. My 180 deg thermostat is full open with same flow rate as fully open 160 deg thermostat.
5. In other words...we both have been driving our Zs for say at least 30 minutes and have reached a steady coolant state.

Now......lets say the day gets hotter. The coolant temperatures should rise the same in both your Z and my Z given EVERYTHING else is the same :yesnod:

If it gets REAL HOT......both our Zs coolant will reach 230 deg at the same time.

The maximum temperature reached (given it is over 190 deg) will be no different for you than me even though you have a 160 deg thermostat and I have a 180 deg thermostat.

I am saying that my thermostat just maintains a minimum temperature higher than yours.
I am also saying your thermostat does not maintain a lower higher temperature than mine. Once both thermostats are fully open, the coolant temperatures are controlled by everything else mentioned in item #1 and not the thermostats (yours or mine).

4. Fans and Radiators.

Same goes for fans......once your fan is on and my fan which may be on at lower temperatures is on.......we have identical radiator cooling no matter how hot it gets outside.

Now if we change radiators.....you run stock radiator and I run Ron Davis....DIFFERENT STORY as I have greater dissipation of heat than you at all rpms (water pump speed dependent) and ZR-1 speeds (air flow dependent).

5. Engine RPM.

1. Fans turn on at 205 deg F and OFF at 200 deg F (Haibeck Chip)
2. I use 180 deg Thermostats.
3. Ron Davis, Dewitt, and Fluidyne multi core Aluminum Radiators.

My experience in all ambient temperatures.

A. In sixth gear running 65 mph (less than 2,000 rpm) the Coolant always gets a bit over 200 deg F. On Hot days the coolant will get a bit over 213 deg F.
The key is the Water Pump is not pushing enough flow through the fully open thermostat to cool the engine to a Temperature where the Thermostat takes over (180 deg F).

B. If I shift to 5th gear at 65 mph (more than 2,000 rpm) the coolant temperature drops to Thermostat control (180 deg F) on cool days and drops to near 200 deg F on Hot days.

6. The Summary is simple.....

The Thermostat is fully open at all coolant temperatures over 180 deg F (no need to use cooler thermostat unless you want to run at temperatures below 180 deg F).

The Water Pump does not provide enough flow to cool the engine at rpms less than 2,000 rpm. This is not an issue at ambient environmental temperatures on cool days. This is a problem on HOT days. The Aluminum Multi Core Radiators DO provide better Heat Dissipation and offer cooler Coolant at ALL Temperatures for which the 180 deg F Thermostat Controls the Flow (above 180 deg F Coolant temperatures the Thermostat is fully open). The Cooling effects then being dependent on Water Pump Flow Rate and Air Flow Rate through the Radiator.

Having the Fans come on at 205 deg F DOES provide for COOLER Coolant in the radiator once sufficient coolant flow rate is provided above 2,000 rpm. Using Aluminum Multi Core Radiators ALSO provides for COOLER Coolant Temperatures in conjunction with the Air Flow provided by Fans and Vehicle Speed. The Heat Removal Rate from the Radiator is greater as the Air Flow Increases and as the Aluminum exposed to that Air Movement increases.

It DOES make a difference if you are moving at speed in conjunction with Fans PULLING Air Flow as the additional Air Pressure Up Front does add to the TOTAL AIR FLOW through the Radiator at any ambient environmental temperatures.

Using 180 deg Thermostats insures that the engine will not run cooler than that temperature since the Thermostat is in control and controls the Coolant flow rate through the engine at all Coolant Temperatures less than 180 deg F.

There has been some suggestions to drill 1/8 inch holes in the thermostat flange to allow better cooling.
Just tested several 180 deg F Thermostats for opening temperatures and found the Stants 180 deg Thermostat will start opening at 175 deg F with complete opening at 185 deg F. Marc suggested at one time the older Stants will deteriorate (Decrease in FUll Open Area) by up to 15% as they age. The Stants tested would be fully open with a flow area of approximately .785 square inches at 185 deg F.

Thermostat opening at 175 deg F....................................Thermostat opening at 185 deg F (Full Open)


A 1/8 inch diameter hole in the flange will 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.

Now 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.

Given the LT5 runs Hotter idling at a stop sign than at 2,000 rpm as cited in Item #5 in the link above a much better focus regarding engine Heating would be engine RPM (which relates directly to pressure on the coolant flow through the Stant Thermostat) and not the Stant Thermostat (Old or New).

See item #7 The 180 deg versus the 160 deg thermostat or no thermostat

[KILLSHOTS]

This is some great input and I appreciate it, guys. Of everything that's been said, the thing that truly alarms me is the pressure issue. I guess I had never considered that. Even without an engineering background, I can see that such a high-compression engine running at high RPM could put serious stress on the non-metal parts of the cooling system without a stat. In this case, the stat makes a more compelling case as a water baffle than a temperature regulator.

Yep, not worth the risk. Thanks guys!

[GOLDCYLON]

Originally Posted by XfireZ51

GC,

What temp does your motor run at?

About 80% of top band is the highest Ive ever seen it go in winter it never goes above 50%

[Dynomite]

Originally Posted by GOLDCYLON

Chris I run a 160 Degree T-stat on my Daily runner. For Phoenix it works well as the days are now in the Century range. Even in the brutal winter season when it gets into the 30s I have zero issues with defrost and heat as well as we all know very well the car heats up rapidly. Keep in mind my car is highly modified engine wise and I run a larger Dewitts radiator and SPAL fans. So your mileage may vary. I do not recommed running without a T-stat GC

Now Daryll

Here is my theory......about thermostats in your ZR-1 with LT5 modified or not and with Ron Davis Radiator or not...I have experimented with it all in 4 ZR-1s

I run 180 deg thermostats in ALL ZR-1s

1. At a coolant temperature of say 190 deg your 160 deg thermostat is open....so is my 180 deg thermostat. So from that point on our coolant system flow rates are identical at the same rpm. And so is the cooling.

2. You in cooler weather are running around with an engine coolant temperature less than my designed engine temperature with the 180 deg thermostat. Your PVC is working at less than optimum temperatures as well as your oil and fuel as Paul explained correctly.

3. See item #1 and item #2 above

Also see Defective Stant Thermostats

Oh....almost forgot.....my fans come on a bit sooner controlled by Marc Haibeck chip to help with engine temperatures when idling at a traffic light on a hot day. But again....my 180 deg thermostat and your 160 deg thermostat are both open in that condition

Cliff

[Bob Eyres]

Originally Posted by Dynomite

1. At a coolant temperature of say 190 deg your 160 deg thermostat is open....so is my 180 deg thermostat. So from that point on our coolant system flow rates are identical at the same rpm. And so is the cooling.
Cliff

True enough. But as I mentioned before, though the 160deg. thermostat is designed to OPEN at that temp, that doesn't mean that it keeps the engine at that temp. Do we know if there is an average temp. differential between these thermostats? Not just during the warmup cycle.

Do we know what the average engine temp, (on a 70deg day), would be on two identical ZR-1's that had 160, and 180 deg. thermostats, after warm up?
And, what is the ideal engine temp, for performance, on the ZR-1.

This question does not apply to the intake plenum, where I think the ideal temp would be as cool as possible.

These questions are important on the LT5 because it seems to respond very noticeably to changes in temp. On a rare cool day here in Florida, after a short warm-up mine runs much stronger for a while until the plenum gets hot.

[Jim Nolan]

I have a 160 thermostat in mine and the fans programmed to come on at 185 and off at 180. In the summer months it normally runs 190, some times 200 in slow traffic. I never liked it stock running at 220-230 and on a really hot day in traffic 235.

[Dynomite]

Originally Posted by Bob Eyres

Do we know if there is an average temp. differential between these thermostats? Not just during the warmup cycle.

Do we know what the average engine temp, (on a 70deg day), would be on two identical ZR-1's that had 160, and 180 deg. thermostats, after warm up?
And, what is the ideal engine temp, for performance, on the ZR-1.

Lets simplify....... You ask a lot of questions but are they relevant?

1. Let us say we have identical radiators, identical rpm, steady state coolant temperature, and both fans on and we are cruising at same speed.
2. Lets say coolant temperature is 190 deg in both your Z and my Z given everything identical in item #1.
3. Your 160 deg thermostat is full open with same flow rate as fully open 180 deg thermostat.
4. My 180 deg thermostat is full open with same flow rate as fully open 160 deg thermostat.
5. In other words...we both have been driving our Zs for say at least 30 minutes and have reached a steady coolant state.

Now......lets say the day gets hotter. The coolant temperatures should rise the same in both your Z and my Z given EVERYTHING else is the same

If it gets REAL HOT......both our Zs coolant will reach 230 deg at the same time

The maximum temperature reached (given it is over 190 deg) will be no different for you than me even though you have a 160 deg thermostat and I have a 180 deg thermostat.

Or.....have I been on the tractor too long

I am saying that my thermostat just maintains a minimum temperature higher than yours.
I am also saying your thermostat does not maintain a lower higher temperature than mine. Once both thermostats are fully open, the coolant temperatures are controlled by everything else mentioned in item #1 and not the thermostats (yours or mine).

Same goes for fans......once your fan is on and my fan which may be on at lower temperatures is on.......we have identical radiator cooling no matter how hot it gets outside.

Now if we change radiators.....you run stock radiator and I run Ron Davis....DIFFERENT STORY as I have greater dissipation of heat than you at all rpms (water pump speed dependent) and ZR-1 speeds (air flow dependent).

[Hog]

I agree with everything Dyno, makes sense. Just a tidbit, lets say your max. temp is going to be 210º no matter the temp of therostat used. If you have a 180º stat, and I have a 160º stat, my car will take longer to reach that 210º max than your 180º stat. Why? Because my stat has started to open at 160º and has been removong heat from teh system, while your car has NOT been removing heat from the system. Assuming all else equal of course.

Your arguements come across as sound to me, but whenever I have swapped from a stock OEM stat to a 160º stat, the engine coolant gauge has always been lower. SO much so, that I swap between my 160º stat for warm weather and the OEM stat for Winter as the interior heat is lacking with the lower rated stat.

There has to be something else at play here. (my experience with stats is not LT5 related-if that matters?)