I have a 1968 RS Camaro with a stock 327/275, 4 speed. I have a strange problem. I can drive the car all day in stop and go traffic in 90 degrees + temperture and it will stay around 180 to 190 degress. but if I get on the interstate and run it at 60 + mph steady, it will climb up to 200. It never boils over , but just enough to worry me. It has a 3 core radiator that I took to the radiator shop and had it boiled out and checked,the cap is a new GM 15 lbs, the Thermostat is a new High flow Robertshaw 180. I had an 18" flex fan on it and several people told me to install a clutch fan , so I went to GM and purchased a new clutch and fan. I also replaced the water temp gauge. The fan sticks in about half way into the fan shourd. It is a stock 327 with a Holley 750 Carb and intake. The best example I can give you was about a month ago, my wife and I went to a car show in Charlotte , NC. Driving back that afternoon it was about 95 degrees. Coming up I-85 we were driving about 65 mph and the tack was setting on 2600 rpms. The water temp was 200, the traffic came to a almost stop because of an accident. We were stop and go for about 30 minutes, the water temp dropped to 180. As soon as we got past the accident and got back to 65 mph the temp went back to 200. Got any suggestions ???

Welcome! Try also posting this in the tech boards those guys are a HUGE help!!

Please only post a question in ONE section. Those are the site rules. This is the right section for your question, it will get replies soon. :)
welcome to Team Camaro too

Do you have a rigid lower hose? Do you have stock pulleys? Any impediment to the air flow through your radiator?

Thanks

Sounds to me like your cooling system, fan, w-pump, rad core and stat are all working as they are susposed to, maybe the w-pump cavitating at rpm... If there was a problem with them they would act up at lower rpm and in traffic. Since the problem seems to be RPM related (check it by using 2nd or 3rd gear and driving around at 2600 rpm).

If it is an rpm issue maybe you are running too lean by the time you get to 2600 or your dist advance isn't working right and it's running retarded at 2600. Maybe even your trans is heating up at rpm and transfering the extra heat...

Both the upper and lower hoses are the preformed, the lower hose has the wire in it .
Ralph

I will try running it at higher rpm and see if it is rpm related or speed related.

I have a 1968 RS Camaro with a stock 327/275, 4 speed. I have a strange problem. I can drive the car all day in stop and go traffic in 90 degrees + temperture and it will stay around 180 to 190 degress. but if I get on the interstate and run it at 60 + mph steady, it will climb up to 200. It never boils over , but just enough to worry me. It has a 3 core radiator that I took to the radiator shop and had it boiled out and checked,the cap is a new GM 15 lbs, the Thermostat is a new High flow Robertshaw 180. I had an 18" flex fan on it and several people told me to install a clutch fan , so I went to GM and purchased a new clutch and fan. I also replaced the water temp gauge. The fan sticks in about half way into the fan shourd. It is a stock 327 with a Holley 750 Carb and intake. The best example I can give you was about a month ago, my wife and I went to a car show in Charlotte , NC. Driving back that afternoon it was about 95 degrees. Coming up I-85 we were driving about 65 mph and the tack was setting on 2600 rpms. The water temp was 200, the traffic came to a almost stop because of an accident. We were stop and go for about 30 minutes, the water temp dropped to 180. As soon as we got past the accident and got back to 65 mph the temp went back to 200. Got any suggestions ???

Ralph..i would not change a thing inho.200*f at 65 mph in 95* ambient is ideal.The engine will be more thermally efficient and boil off moisture accumulated in the crankcase.

at what temp should I get concerned,

at what temp should I get concerned,

Concerned about 215 /220
Shut down 235 thats the stock gm idiot light temp

If you drive at 75 for a period of time, does it get even hotter or stay in the 200 range? If it does get hotter, then maybe take a trip to a dyno and run it there. They can check your A/F ratios at different cruising speeds and see if it's a lean condition.

Temps shouldn't be an issue at 200, but if you're running lean at those rpms, then you should get that fixed.

Concerned about 215 /220
Shut down 235 thats the stock gm idiot light temp

I agree with Steptoe^.Lt1s, with tin heads atop an iron block only ramp up fan speed when coolant reaches 228* f.You are good to go with idle temps at 185 and cruising at 200*f.Your engine will thank you for operating in these ranges.Reduced wear and more thermal effiency.IMHO,in a perfect world..our dated engines would have hot blocks and cool cyl heads.Anyhoo..enjoy your ride..you have no cooling issues at legal e-way speeds.

I would agree with Steps and George if his temps didn't drop back down when in traffic and at slower speed/rpm...

Thanks for everyones comments, I drive this Camaro every Saturday to a Cruise in and I love driving it.
Ralph

Even so it should not behave this way
Normal behavour is runs 185 to 195 on highway and around town
After a long highway run, come off , stop and idle at interesction, the temp should go up to 200/210, then settle back.

It has a 3 core radiator that I took to the radiator shop and had it boiled out and checked
The CORRECT method is not boil out, this will not remove bits of rubber, sealant, old broken hose spring that has compressed into the lower cores.
The headers are removed and the cores are manually ceaned with steam, and a auto dip stick.
With the engine cold, fire up, increase rpms a little on the carb idle screw, and run your hand over the radiator, as the engine warms up it should heat up evenly...or in other words u will not feel cold cores.

The oly other issue is maybe the impeller in the water pump spins on the spines at higher rpms...when moving more water
This has the potentual to suddenly stop pumping water, murppy steps in and u will be in the middle of know where

I would lay odds on a few more than a couple blocked cores,,, the stock radsitor is way over built, a couple blocked and restricted core doesnt make any diff.

Re check the bottom raditor hose, squeeze it...should no be able to squeeze it.

I agree with you , I have never seen a car do like this, I will check the bottom hose again. I will add one more thing to this, in the morning when it is cooler I can run it at 65 mph without it heating up, but in the afternoon when the humitity goes up is when it starts to act up ????

68 RS Camaro , matching # car, 4 speed, 327 / 275, Lamans Blue, white interior.If I knew how to insert a picture I would send you a picutre of my pride and joy. I spent the last 3 years restoring this car.
Ralph

I just went out in the garage and started the Camaro, the radiator stayed cool all over until the stat opened at 180* then the tanks heated up evenly .Even before I started the engine, the bottom hose was stiff, but after it heated up and the stat open it got very stiff. I increased the rpms up to around 3000 and held it for a while and watch both hose, neither nose clasped. I am starting to question the water pump? Another question, at what speed or rpm does the clutch fan stop turning or does it stop.
Ralph

I agree with you , I have never seen a car do like this, I will check the bottom hose again. I will add one more thing to this, in the morning when it is cooler I can run it at 65 mph without it heating up, but in the afternoon when the humitity goes up is when it starts to act up ????

68 RS Camaro , matching # car, 4 speed, 327 / 275, Lamans Blue, white interior.If I knew how to insert a picture I would send you a picutre of my pride and joy. I spent the last 3 years restoring this car.
Ralph

The ability of your radiator to dissipate heat is directly affected by the difference in temperature between the radiator and the ambient air. When the ambient temperature rises, the efficiency of the radiator goes down. In order to dissipate the same amount of heat, you must raise the average temperature of the radiator. If your thermostat is within its control range, it will open farther and raise the rate of coolant flow, raising the average temperature of the radiator. If the thermostat has reached the limit of control, the inlet temperature of the radiator will increase until equilibrium is achieved.

I agree with you , I have never seen a car do like this,
I have, many times over the last 30 odd yrs..including mine
at what speed or rpm does the clutch fan stop turning or does it stop.
Forget the clutch fan...at highway speed, even with no fan, there is still more than enough air to keep cool
ambient temperature rises, the efficiency of the radiator goes down
In practical terms, ambeant temps at most will have very little (0 to 5 degs) on the water temp...these radiators are so over built.

Thermostat...these are not made equal, so expecting to just buy a 180 off the shelf doesnt apply
The rate and tamp range thay open at varies to application, as does the totla area of the opening
SB chevys are sensitive to how far they open, even smoket back in his days covered the subject in detail....drill a 1/8 or 3/16 hole in the top of the thermostat housing.

In practical terms, ambeant temps at most will have very little (0 to 5 degs) on the water temp...these radiators are so over built.

As I stated earlier, this would mean that the thermostat is in it's range of control. If it does not respond to the increased temperature by allowing more flow, the inlet temperature of the radiator must rise and raise the average temperature to dissipate the added heat.

How do the plugs look is she running a little lean??

I pulled the plug out about a week ago, they all looked good, they were not white looking but they were clean and free of oil.I have them gapped at .035.