I am seeing a lot of posts on here about "temperature issues".
Thought I'd put the question up for discussion. Personally, I think many folks are worried about nothing. If the temp goes above 220 WHILE DRIVING, then I'd start to worry. My 2004 Chevy truck runs at 210 all day long with no problems. That's in hot humid 95 degree days and sub-zero days.

My opinion, anywhere between 170-220 is a safe zone. Note that it's also not good to run too cold. The engine has a certain "efficient range" that it should run in. Note also that engines with pollution crap on them are made to run hotter to help control the pollution.

Dep

 

Dep,
Of course I am old school, but I agree anywhere from 170 up to 220 is common for older Corvettes to run. The newer vehicles are made to run at higher temps and are more efficient at those temps. I think the primary reason everyone wants to get get the C3's running cooler is that the cockpit is cooler. I can run my '79 at 70 MPH turning 3200 RPM and it is very warm inside the car while the engine is running at 180 degrees. I can slow down to 2300 RPM, the engine is still at 180 but the inside of the car is much more comfortable. I don't believe it hurts the C3's to run at 200 degrees, just the people driving them. Now, I have done a lot to cool the inside of mine and don't mind driving around town or for several hours on the interstate, but plan on putting in either a 5 speed or overdrive tranny to get the RPM's down for the longer trips. I think that is where most people are coming from when they are concerned about their cars running hotter. Now I know that the C3's will tend to get pretty hot in stop and go traffic and people tend to get scared when they see the temp guage begin creeping up past the 220 mark sitting at a red light. I suppose that is why there are so many aluminum radiators and electric fans being sold; so that, no matter what the condition of traffic, stopped or moving, they never see the temp go up. That is my feeling on the whole temperature thing.
Bernie

 

Dep -
Here's a perspective: The early C4 Vettes use a plain ol' cast iron 350 identical to the C3 engines (except with FI). The cooling fans on a C4 are ECM-controlled to not kick on until 230.... My '85 runs 217 to 230 in the summer with the AC on in traffic. It will occasionally hit 240. No problem until it hits 260.

 

I'm switching to an alum rad because the original is leaking. It's been leaking for the past 5 or 6 years so its about time for a new one. My temperature would normally alway stay below 210 even on hot days. I believe that if starts getting up to 220 and higher, there may be a problem somewhere.

 

Dep,
My 1967 runs 180-190 consistently (180 t-stat with Al rad and separate auto transmission cooler). My 1979 ran 200 or so in the city and on very hot days at speed on the highway it would touch 220. That never worried me. I got best start-up performance with the 195 t-stat. In fact if you go to a GM dealer, that is the only t-stat listed in the parts book.

Two observations on the 1979. The red zone on the temp gauge was 250-260. The optional auxiliary electric fan sensor was designed to kick in at 238. While I would be worried if the temp went over 230, it would seem that GM built in a capability to operate safely at that temp. I suspect that one would see that condition (238) at highway speeds with the A/C on and towing a trailer. Also keep in mind that C3s (with TH400 or TH350) do not use a separate automatic transmission cooler so in a sense the rad is doing double duty.

 

I'll operate the engine at whatever temp is best for POWER, not comfort, not efficiency. Anybody know what temp that is? Facts please, not anecdotes.

I've got mine set at 180, but will be happy to move it to 325.7 if that's what the dyno says provides the most power.

 

I wouldn't want an engine to run lower than 175-185...180 is ideal. Gas and oil need the heat to perform more efficiently and at its best performance.

 

I've got a buddy who runs a Reher-Morrison 572 in a strip-only Camaro. R-M recommend making runs with the engine DEAD COLD...

 

I like 185. That is where the gas atomizes the best, I don't feel I am going to melt the engine down, it is hot enough to vaporize the water in the oil , cut down wear on the engine and my engine seems to stablize there without a thermostat.
I have seen wear charts and at 160 wear in the engine is alot more then at 185.

 

I have a complete stock setup:Clutch fan,195 degree themostat,and The Harrison Rad W/15 PSI Cap.
Worse case for me is in the desert pulling a hill at 70 MPH and temp goes to 210 with A/C on.On the west coast at 70 MPH I'm getting 200 degrees no A/C on.Around town,traffic,etc below 55 MPH,gauge reads 190 or so no A/C on.
I'm getting a Raytek Minitemp MT-4 infared temp gun to find out what I'm really getting.

 

Cool input!!! (pardon the pun...I rarely pun, so I take every opportunity

Bernie: I didn't take into account the human comfort factor in my question. It certainly makes sense the way you decribe things.

Lars: Good to hear from you!!!
I'm lost with the newer electric fan setups. I had one on my '98 Vette and it seemed to work fine. Also had one on my 2002 Monte SS with the sideways mounted engine. I could actually sit at idle and see the thermostat go up to a certain temp and then the fan would kick on and the temp would drop back down. Pretty neat. I'm a big fan of the fan clutch (oh geez...just reached my pun limit). I've had cars that came with just a 4-blade fan and when I switched to a clutch setup with 6 blade fan the temps took a noticeable drop.

I'm not sure about aluminum radiators and if the extra expense is worth it. I'm sure they cool better. Just not sure that extra cooling is really necessary.

Paul's 185-190 is probably what I would shoot for as an "optimum" temp for my use. Don't think I would blast off down the strip with a cold engine. Maybe using 5W30 oil it would be okay. Just seems risky to me.

Dep

 

"I'm not sure about aluminum radiators and if the extra expense is worth it. I'm sure they cool better. Just not sure that extra cooling is really necessary."

DEP.The aluminum rad is more efficient than the copper/brass.But my view is you must consider the whole system,not just one component.Fan clutch is my choice as well.

 

Rich: I don't question that the aluminum rad is more efficient. I just wonder if it's worth that extra hit of $$$ to get that extra cooling.

Dep

 

Depends on the deal. I got an aluminum from a well known forum vendor for only 76 dollars more than the stock replacement would have cost me. In a situation like that its a no brainer. However without that deal I would have got the stock replacement and been just fine with it. I am not running a powerful motor (yet) but when I do, I will have the radiator to cool anything.

I also agree that the temps of the engine don't bother me as much as the temps inside the car. Heater core shut off is a must for nice weather driving.

 

Guys,
I'm running twin 12 inch electric fans with the engine clutch fan too! Have the shroud in place and the original style radiator. I did put an external transmission cooler in front of the radiator. This system works well for me. It looks original and it cools adequately. If I ever had to replace the radiator, I think I would go aluminum if I could afford it at the time. I think the most important things are to make sure you are forcing every ounce of air you can thru the radiator, not around it and having a system that flows the coolant thru the system and holding it long enough to cool it to the proper temp. Things like aluminum water pumps, aluminum heads and intake, aluminum radiator, sealed shroud and rad. support all go toward making a more efficient system. The question is, how much are you willing to pay for these high priced components? I try to upgrade as I need to replace them if there is sufficient benefit.
Good thread. Bernie

 

Hey I got a question,

I was running between 200-220, but since I rebuilt my carb and tuned it up I am now running at 175 all the time. Does this make sence or is the sensor/gage bad?

1969,350 300

 

I caught that.But if I were drag racing,I would go with aluminum for efficiency/weight and would understand there will be expenses beyond doing just cruising,like I'm doing now.In my case, I'll stick to the stock rad,which is not cheap,btw,for the correct one...

 

I think our 1968 454 BB never goes below a constant 220 when it's warmed up.. is this a bad thing, or do BB generally run hotter? We havn't driven it for a while because of engine rebuild and misc, but will be getting it on the road within a few days, and would like to know if we should be looking at the temp in more detail now ..

Thanks,

Kosta

 

My 98 trans am never goes over 190. I like it that way.

I am going to work to keep my C3 in that range when I get some cash

 

Here's an intertesting quote from the Jeg's Engine Masters article in Popular Hot Rodding:

"The MPG boys made it to the finals and say their dyno has proven that every degree above 160 degrees coolant temperature drops horsepower output by one point."

I would think that engine temp would affect power as a secondary heat gain to intake air as it passes through the (hot) intake runners and head ports.