…Here’s one for you:

Does anyone know ‘THE OPTIMUM TEMPERATURE’ that a C4 should run at?

I’ve heard and read many times that "C4 engines were designed to run hot"; but WHAT temperature IS that precisely? I know the cooling fans are designed to switch on at 220’F or something like that, but that cant be THE optimum temp surely…Anyone?

 

Optimum may not be conducive to longevity. What is your optimum result, performance or longevity?

 

i'm not even touching it

 

Chickensht.

 

optimum?

optimum for the end user, or,
optimum for GM?

 

I will. The optimum temperature for a daily, street driven 93 LT1 is between 205 and 225 degrees. How do i know this? Well, that's what my vette (all stock) usually ranges... but how hot it's running entirely depends on how i'm driving it.

There is no precise number that is "the" optimum temp, but I figure if anyone knows anything about optimum temps it would've be the guys at GM who were building the ultimate American sports car.

I'm pretty sure operating temperature was a factor in developing maximum performance from the engine.

 

Good points...I guess I lined myself up for that, didn't I?
I suppose without getting into a 'Metaphysics of Quality' 'argument'; I meant a little of both as well as economy - or more precisely - optimum longevity/performance equilibrium.

 

Thanks mate; that was more the kind of answer I was seeking.

 

@ 240 your car is getting too hot! Mine will go to 223 when sitting in traffic.

 

...I don't believe anyone has mentioned 240', but thanks for your input.
As a rule (and this is rather dependent on ambient temperatures) my 'Vette can go anywhere from about 174'F (79'C) or slightly less, on a mild day or cool night, to around 212'F (100'C) on a HOT day...Maybe a smidge higher at a slow set of traffic lights on a hot day.

 

Here goes lol-do some research on thermostats on the web-test after test shows the optimum to be guess what??? 180 for all out performance and engine longevity on SBC, Guys wanting to go for all out power should look more at cooling the induction system than going
with the -I'm gonna say it-160 thermo. All the info is free-just go read it.

 

Yep; good old 160' thermo; I have one in mine, but isn't it amazing; the temps I stated above are STILL higher!

Good for faster or slower warmup's, after that the thermo is just another useless item

I cooled my intake down a little by insulating UNDER the air filter housing, which seems to help due to rising radiator heat...As 'Rippley' used to say; "Believe it............Or not"

 

So what makes wear greater at lower temps?

The piston to bore clearance is greater, the metals are harder...

Its a powerplants problem.. nothing more.. nothing less.... GM can get better emmissions and fuel economy by running the engine as hot as possible.

For the racer keeping the heads and intake as cool as possible is going to yeild the most power.. If you don't believe me put a car on the dyno.. the first 4 runs will back each other up +-3/4hp or so (as long as it doens't get into knock on one run) put another 4 runs on it and you'll be down at least 10hp


I talked with the guy who runs the Dynojet for Hendrick motorsports here in concord and he said the same thing.. A street car can't move its heat where it needs to be and keep it from where it doesn't need to be. He said, they run the racecars on the dyno for about 30 minutes then make a certain number of throw away passes.. then 7 test passes.

The nascar guys don't take a pass or two down the drag strip.. they run the cars for hours at a time.. so the learn to use the heat to thier advantage rather than us trying to fight heat out.


BTW.. they told me they shoot for water temps around 230 degrees and the oil temps closer to 300.

You'll start to see heat to hurt a L98 around 195 on the dyno, a LT1 around 185, and a LS1 around 200.

 

You just made the point is was going to Alvin.What temps are people talking about water or oil?There is a big difference and I watch the oil temp I could care less what the coolant is as long as the oil temp looks right and I don't see steam coming out.To me that is what the engine is running at.

 

That is the MINIMUM temperature. The thermostat does not control the max temp. (see the tread I want to rename te thermostat, very good explained) and the actual temp is somewhere inbetween this temperature and the temperature the fan kicks in. If you want to control your temperature more closely, you should mount a fan controller that switches in slightly above your minimum temperature where the thermostat opens. Keep at least 10 degrees C. between those two in order to avoid temperature hunting between thermostat and fan. If you want, you can control the fan electronically really quite easy without interfering with the excisting system.

 

When I got my 85, it ran at 220 running down the road, 235 at lights....

I pulled the radiator, cleaned it out, and cleaned behind it. Got the temps down to around 212-225.

I then changed out the t-stat to a 185 degree one. And it then ran around 200-210.

Recently my fans stopped working...replaced motor.

Then I installed a kit from ecklers that makes BOTH fans come on at 195, and off at 185...+/- 5 degrees.

The car can sit in traffic, and never ever get above 196. I can lay on the car, 0-75 runs, really beating on it HARD and never get over 201.

 

If you ran cooler with your new hermostat, the old one did not open up as it should be. The thermostat can not control the temperature well above its opening value. It is a good point though, it happens quite often. People should renew their thermostat once in a while.

 

croosfires should run at lower temps than LT type engines, I have had crossfires in a Z28 and a TA and both normally ran in the 190-200 range. My LT1 runs in the low 200's normally and when I have the AC on it runs a little rough and when the temp gets down around 180-185.
I would try to keep yours under 200, but over 185-205 for optimum fuel economy and around 165-175 for performance.

 

Hey thanks for that info Randy, did not know that. Now I can set it where ever I want it with my variable temp. fan switch.

 

I believe the crossfire is setup to run in the range I discribed, if it doesn't, clean your radiator out, drain and refill coolant.
If that doesn't do it, I believe your crossfire still had the fans turned on by the coolant sensor, if so get a sensor that kicks the fan on sooner.
If it is turned on by the ECM, you will need to get a chip burned to get the fans on earlier.