1972 350 / Automatic - stock- - new hoses, Radiator flushed, just had Q jet rebuilt, new intake manifold gasket. If the car idles the temperature stays at 190. On the highway so long as I'm on the flat it stays around 195 however once I start up a hill and put a load on the engine the temperature rises up to 200 - 205"?... Ideas?

Thanks in advance!

 

The easy ones are:
Timing.
Radiator seals, the sides and top, if you have an ac condenser.
Lower air dam, I put an extention on mine to stop rising temperature at 70 MPH plus.
Thermostat.

 

Of course its going to get hotter pulling a hill. Do you think its supposed to get cooler under a heavy load? What you're seeing is perfectly normal for any engine.

 

Never did it last year. The load is one thing but the 70 MPH breeze should counteract it. If I were pulling a trailer maybe.

 

Considering what you changed since last year it could be the Q-jet is running a bit lean? Flushing radiator, new hoses and intake manifold gasket should have no effect on the running temp.
Distant second possibly intake manifold gasket did not seal and you got a vacuum leak making some or all cylinders run leaner.
Check you plugs for clues to running too lean.
Change anything else? Like timing when you put manifold back on?

 

i would check the timing first, when i got my 74 it would overheat whenever i would drive it hard or in traffic. i checked the timing, set it to 36* total timing, and threw in a 180* thermostat and has not seen temps above 200 ever since. also helped solve a little backfire it had as well

 

Check to see if you got a bunch of junk in front or between your ac/radiator. Also like said timing since you had the intake off.

 

I suspected the Q-Jet running lean at first. I will check it and the timing. The static vac advance timing is good but I did not check to see what it is doing at higher RPM. Nothing in front of the radiator or A/C. Thanks for all your help! I will update when I solve the problem!

 

My 66 ran cool then it was over time getting a little hotter a little hotter, I didn't know the condition of the radiator and did the flush thing, ( you said you flushed yours, why? )
I was heading on a 150 mile trip and on the highway when I would start pushing it the temp would creep up, by the time I got where I was going I could not drive over 35-40 MPH without it creeping up, the radiator was shot, it looked okay but it was spent, a new one fixed the issues ran cooler than ever.
Not saying that this is your problem, and all the things other people listed can and do cause overheating problems but many time if nothing else is changed and an over heating issue just creeps up might be the radiator itself which seems to be ignored many times.
Even years ago with my 66 I didn't think it was the radiator.

 

200-205 isn't that hot... But you might try a cooler thermostat. Make sure the thermostat has no restrictions... make sure your fan clutch is working good and not slipping... And I'm assuming you are running a stock fan?

Things you could do if you really want it to be cooler...

Add an auxilliary electric fan.
Add a transmission cooler.
Switch to an aluminum radiator if you have a brass one.
If available switch to a larger radiator.

On the transmission cooler you'd be amazed at how much heat an automatic transmission puts out. Stock it dumps that to your main radiator. An add-on cooler will help take some of that load off the main radiator.

 

you never said what thermostat you have 160 ? .... 190 ?
if everything is working correctly you should be able to maintain very close to your T-stat temp.

 

I have a 190 degree t-stat, original radiator. I am goi g to try a new t-stat even though the one in it is less than 1 year old and make sure all the air is out of the system. Adjust the Q-jet and re check the timing. If none of that works I will look into a new radiator. The trans was gone through last July when I purchased the car. Thanks again for all the ideas. I will update when I figure it out...

 

I purchased the car last July and changed all the fluids ( except brakes and rear end) - this winter!

 

I have 180 high flow thermostats in all my vettes. the 1972 runs 175 all day, even with the a/c on. The 71 runs 170 all day - 5 speed car. the 85 runs 180 a/c off, 195 a/c on in traffic, 180 highway - 383/6 spd.

I agree the rad and hood seals are key, as is the air dam.

 

Putting in a different t-stat will change NOTHING. The t-stat only sets the LOWEST temperature that the engine will run...not the highest. Once your engine reaches thermal equilibruim, it will be what it will be.

Timing too retarded, lean carb and/or leaky intake gaskets (sucking air) would be the most likely candidates.

 

I had a low cost stat in my 72 which ran hot. The HIGH FLOW stat allowed an increase in the flow and lowered the temp.

Same for all 4 cars.

If he is running a thermostatic fan, the fan could be worn out, as you said timing issues and a lean mixture can cause issues.

Cracked head, spun bearing etc.... unless he uses a thermo gauge to check his dash temp gauge, he is assuming a more severe problem.

Hopefully he started with the basic - see if the belt is slipping and there is good flow when looking in the radiator cap.

 

I do not have enough info to say 100% it's a bad radiator but the simply fact is engine tuning, seals, gaskets etc can only do their job if the radiator is up to par.

 

200 -205 isnt going to hurt your engine. I don't personally like it that hot but it will be fine.

If your tstat is a 190 then you should expect that engine to run at least 190 given that is the point where the stat will open up. 190 doesnt give you any reserve for loading or exits off the highway on hot days where the temp can jump ... thats why I like to run my engine cooler.

I have a 160 stat in my car with electic thermostatically controlled fans that go on a 195 and off at 175. Idling my fans will cycle on and off at those temperatures. On hot days it cycles more on cool days it cycles less. Driving at speed my fans do not come on unless in stop and go traffic. If i force the fans on the lowest the temp will go is about 160 due to the 160 stat.

Given that you state the car did not do this last year then look at what you last changed. Your carb could certainly cause you to run hotter if its lean (but did the performance change?). At speed the air rushing the radiator should do more than any fan will provided you have the seals around the radiator.

Check that your lower radiator hose has the spring in it (most new hoses dont come with them and some folks leave them out) ... if not it could collapse under higher rpm.

The next cheap thing to do is remove the tstat all together and see how it works temporarily (if you like touching your coolant twice) or just change it with a good quality high flow 160 as they are inexpensive and I hate messing with draining coolant. (I like to drill 3 small holes in mine for easier bleeding of air when refilling but its main purpose is that my intake doesnt have the bypass hose to the pump).

 

I am with Bats on this one, saying the rad is prime suspect. For temps creeping up. Also do the 180 therm with small holes drilled.

You said the rad seals (esp the rad support to hood!!) were OK?? And lower air dam?

 

It does not sound like anything is bad or broken because 190-205 is a good temp. Since you were running cooler last year prior to a carb re-build and intake gasket replacement, I would make sure your not running lean, that will effect your cylinder temp when under load and so will the timing being off.
Also things do break or go bad, so how something is last year does not mean it will be the same the following year.