I have a 67 conv. with 427/400, A/C, PS, PB etc. I have had nothing but problems trying to fix the overheating problems. THe radiator was replaced, a 160 thermostat installed, fan clutch replaced.... The car operates fine at about 210 but after a few more miles of driving it begins to kreep up to about 240 - without the A/C. It pukes its guts when I get home. I have tried an additive to try and cool the antifreeze down but it still doesn't work. Could the fan clutch be bad? I know the thermostat opens and the system has been pressure checked. I don't think there was a coolant recovery system for this car in this configuration? It is mainly a show car but it would be nice to get the heat down - especially when you love in Austin TX!! Any help out there? Any thing I can add without major modification?

 

Thermostat has nothing to do with operating temperature - only sets the minumum temperature if your cooling system has the capacity to cool the engine below the thermostat rating (which most don't). Fan clutch also doesn't affect highway cooling - only at idle and in slow traffic, and the bottled additives are pretty much "smoke and mirrors".

What kind of radiator did you use? Highway-speed heating is almost ALWAYS a result of a radiator with inadequate heat rejection capability (barring things like a blown head gasket or airflow blockage in front of the radiator or a lower radiator hose that's collapsing at cruise rpm due to the internal spring corroding away). Your combination in particular (BB w/AC) had very little cooling "margin" originally, and if the new radiator isn't at least the same capacity (in terms of actual heat rejection capability, not just "size"), it'll never cool on the highway. I'd bet your radiator "fits", but doesn't have the cooling capacity to handle the load it's seeing. :thumbs:

 

well, whatever you do, don't add electric fans and BS like that..... or "water wetter" lol.

air cars had extra seals to maximize the systems performance...... do you still have them in place? (seals around raidator/shroud, and on top of the rad support....... to direct as much air as possible thru the radiator, instead of around it.) if you really want to do it right, get a Griffin HP radiator (sell the one you have), put a 180 thermo in it, make sure the pump is ok, and freshen up the air seals refered to above. ....... you should be all set

do some archive searchers...... a lot of good cooling system info there

good luck :seeya

 

Had the same problem. Check the archive forum threads for an almost infinite set of info on this problem.

My problem was fixed when I finally changed the vacuum advance to provide more advance at idle. You apparently need to have high advance at idle to keep the exhaust gas temp low. Otherwise it heats up and pukes even with new radiator and water pump.

Good luck,
Mark

 

HOw "much" advance are you referring to? Setting the timing where from factory settings? I have installed electronic (hidden) ignition. I am a novice at this (as you can tell). Thanks for your help!! :party:

 

I'll check the seals around the radiator. THe car had a frame off about 3 years ago. I know the upper rubber strips are there but have not checked for the lower.

Also.... isn't the license plate supposed to mount on the drivers side instead of the middle. Mine is currently in the middle and might be interfering with air flow? :steering:

 

With AC and auto your car should have a mild enough cam to pull good vacuum at idle and use the stock vacuum canister. Check to make sure it's in good operating shape and hooked up to a full time vacuum nipple (not the ported vacuum nipple). You want the one that has full vacuum at idle. This forum made a believer out of me after doing this on my 66 big block. It runs much cooler in traffic now. I passed the tip on running vacuum advance to the Moparts forum and one guy reported it dropped his running temperature by 30 deg. :steering:

 

I installed a BeCool radiator and switched to an Edelbrock water pump. These changes have helped lower my L72's engine temp by at least 30-40 degrees. Just my 2 centavos....

 

JohnZ is right about the radiator, however, you did not really say what type of driving you were doing when it reaches 240 (and pukes). If you are at low speeds (traffic conditions) then your fan clutch ~could~ be contributing to the problem. If it is highway driving, then I would definitely look to the radiator as the most likely culprit. Proper tuning is also a must (vacuum advance, timing, etc.) Vacuum leaks, in general, can also contribute to a warm running engine and worth investigating as well. :cheers:

 

...i also have a bb/AC and solved my problems by going through the basics - i tend to agree with JohnZ, from the sounds of it, it's not your timing and you need to check to ensure you have the correct application radiator ( i run a recored harrison)...

in your part of the country, you can run water - no antifreeze - and add pump additive (a must) and water wetter (which has noticably and consistently lowered my water temp a few * from maximum - sorry guys, this one works for me)...ethylene glycol is a relatively poor conductor of heat, when compared to pure water....when you flush your system, also pull the block drain plugs...you do NOT need a fancy water pump, a decent after-market aluminum standard flow pump works just fine...even if your cooling system is marginal, switching over to the water/mix will cause a noticeable improvement in lowering the high-end and ensuring more rapid recovery...

..one thing missed here is to ensure you have plugged up all the holes in the fan shroud - not just adding the AC top flap and foam insulation (note that the factory AC cars also had a lower fan shroud extention to increase fan efficiency (i've only added one ever and i had the shroud out)...i use HVAC cork tape to seal the shroud with great success.......

...i also use a direct drive original big block fan (deeper pitch than a small block fan - but you'll be fine if your fan clutch is working OK) - if you are using a flex fan - it is junk, throw it away...

...before my engine rebuild, i added TEL to the gas during the hottest times of the year and that also dropped the temperature noticably and completely eliminated detonation that would occur when stopped at along light)...

...the front license plate holder moved to the driver's side on a bb with PG - i've moved mine BELOW the center of the front license plate bar by attaching the plate from underneath with a piece of aluminum 90* stock...lots of ground clearance...

...resist the temptation to not run a tsat at all - i don't care what anyone says, you need to get the engine up to 180* as fast as possible to ensure all the gasoline stays vaporized

good luck

 

All GOOD suggestions. I'll add one more, the radiator itself. It might not leak, but also it might not "flow". Is it correct for your car? How sure are you about it.

BUT, here's another point, that I've seen with show cars. They paint the radiator "to the max" to make it look pretty. Some have so much paint in, on and around the fins that it interferes with heat transfer. Just a thought. Chuck

 

hmm...THAT is a good point about the paint...also, what about the REAL entry-level stuff like looking for ANY obstructions in the fins, are they aligned, etc, etc..


...those aluminum radiator fanatics ought to lie down 'till it passes - having paid attention to such basics may have saved a few of them 700 bucks or so..... :rolleyes:

 

I have a big block but no air. I also have a 8-71 blower on the motor so keeping it cool can be a problem.
The subject of running without a thermostat and with has been beaten to death on the C3 forum. I do my own testing.
I have 2 temperature gages, one in each head. My thermostat also uses an O ring gasket so it is easy to replace the thermostats.
I have it down to a few minutes to change in or out and I have run extensive testing. Today it is in, tomorrow it is out, the next back in and so on for a couple of weeks.
I found the engine run alot cooler without the thermostat, but I only drive in nice weather, never cold and certainly never in the winter. Only the hot summer months.
I also found the heads ran more even temperature without the thermostat. When the engine was hot and I made a pit stop of say 5 minutes and restarted the engine and drove away the right head would stay hotter for longer then the left head. Without a thermostat the temperature equalized alot quicker.
I now run without a thermostat, I run the high volume TRW aluminum water pump 30% faster then the motor and I have twin electric fans switch controlled that are only used in town.
On the open road I run no fans and the motor stays below 190.
So for me I do not recommend a thermostat for warm weather driving and for me it has proven to run cooler.

 

The license plate was repositioned at the factory only if the car has A-C and Powerglide - both of which put radiator preheaters (exchangers) in front of the radiator. I lowered mine to hang under the cross bar - but that only helps high speed overheating. :lurk: