As you suggest, I too considered the possible change in fan/shroud geometry so prior to installing the replacement fan clutch, I measured both of them in height, width, diameter etc etc and they were equal. The only difference I noticed was in the length of the pulley mounting stud. The reproduction fan clutch stud wasn't as long as the original. Not by much but noticeable. Since it (the stud) goes past the face of the pulley and into the water pump pulley mount, its length, for this discussion, seems irrelevant. I'm curious to know if anyone can assess the measurements I posted regarding the fan as it sits in the shroud. I think the shroud is the original, Certainly on my 34 year watch it wasn't changed. Thanks toddalin.

 

Interesting you mention Haydens. Originally I did buy a Hayden 2711 from Rock Auto. One because it was less expensive than the reproduction and two, it claimed more efficient cooling. When it arrived, it just looked so different; larger diameter, center coil spring, and larger fins. I sent it back and ordered the repop from Paragon. This Hayden has the coil thermocouple on the face of the unit. The original was the Schwitzer style as is the Paragon. Far more expensive than the Hayden but it mattered enough to me. It's possible it isn't working as you suggest. I didn't pay attention to it when I shut the engine down. I was busy looking for coolant leaks. I'll run it again and see.

 

Call me crazy, but I'm going to guess it will.

 

I would measure mine, but the shroud is not an oem piece and I use a 7-blade Hayden flex fan on a solid spacer. I can tell you that it is so close as to rub on shroud (been relieved a hair) the driver's side with little room on the passenger's side.

BTW, one more thing. I assume that you replace the thermostat. Did you first drill a small hole in it?

 

"BTW, one more thing. I assume that you replace the thermostat. Did you first drill a small hole in it?"

I did not.

 

If that did anything for you, the thermostat would have come that way.

 

Drilling the thermostat helps burp air out of the system when you fill it with coolant. Not sure it helps in any other way.

 

I would like a thermostat that is fully open at 180 degrees. Running an old Rochester unit I would like all the help I can get. Any idea on a thermoset that is full open at 180 degrees?

 

The rated temperature of thermostats is the temperature at which they begin to open and full open is usually another 20-30 deg. F, so you might want to run a 160 if you're having severe percolation or vapor lock issues, but keep in mind that lower operating temperatures will not boil out crankcase blowby contaminants as well, and it's worse if there is just a road draft tube and not an effective PCV system.

Duke

 

I run a 160 degree thermostat and the car usually runs about 165 on the gauge. I like the lower temp because when you get stuck in traffic, if gives you more leeway before you start to worry about overheating.

 

Get rid of that B1 VAC can and use the 2 inch rule based on your vacuum at idle. Switch to direct vacuum, not ported.

 

It looks like I'm headed that way...replacing the B1. I believe I'm already at direct vac with the stock carb fitting below the plates.

 

Is your coolant at the proper level? Maybe try put in a bit more and retest, and if it starts to puke it's guts on hot soak, you've gone a bit too far.

 

Coolant level is correct. Over the weekend I'm going to start it and take temp measurements with an IR gun, do manifold vacuum at idle check and checking initial timing. I'll post that data here. If I can get a vac advance curve before it overheats, I'll have that too. It's supposed to be smoking hot here this weekend so if it behaves badly, I may run out of idle time.

 

I am going to move another direction here. There are many old Chevrolets that do not even offer vacuum advance and they do not overheat. They are not as efficient, that is fact but they can be daily driven and do not overheat. I say this because I would tune the engine to good known specs. Timing must be correct and your distributor advance must be correct. Basic timing should be close to 10* at idle and advance smoothly to 34*-38*, it should max advance no sooner than 2,800 or so and be fully advanced by 3,500, some Corvettes keep advancing till 4,000 and that is fine but we know now that all advace in my 3,000 to 4,000 works fine. You can't have any vacuum leaks that cause a lean condition. If the basic tune is correct you can drive it with no overheat. At this point you can add vacuum advance to enhance your engine. Yep the vacuum advance can help it run cooler but the way you are describing your overheat it sure sounds like you have a problem causing too much heat and I don't think it is your vacuum advance.
For you to worry you won't be able to set your vac advance curve before it overheats tells me you have a larger issue to fix before getting to the Vac advance. Trust me, I know the Vac advance helps an engine perform more efficiently but you have other issues if you can't idle for long without overheating right away.

I would be checking circulation, check temps as your coolant enters the radiator at the Top and check temps as it takes coolant back to the engine at the Bottom where coolant is pulled back into the engine from the radiator. You should see significant temp drop. If the temps are cool headed back to the engine from the the radiator that teaches you something. If the Radiator is not pulling the heat out the lower and upper temps will be nearly the same. I think more information needs to be learned on this engine. The information found from investigation should point to the actual problem.

You can check the coolant for hydrocarbons, there are simple inexpensive test kits sold at most auto parts stores. If you have hydrocarbons you have a leak, either head gasket, head or block allowing combustion into the coolant. You should be able to start your cold engine and idle for at least 30 minutes without ever overheating, you do not create much heat at idle. In reality it should be able to idle and stay cool a long time when you start with a cool radiator.
You can mist cold water from a hose onto the hot radiator, that alone should pull 20* out of the radiator very quickly, maybe 2 minutes, it is more effective than a fan. If that does not cool your engine quickly you learn more.

 

Early last night I ran the engine to get some data. Starting with an ambient temperature of 92*, I ran the car for 25 minutes and shot temps along the coolant path with an IR gun. Upper and lower radiator hoses varied between 6*-8* (198* & 192* after approx 23 min) once the 180* stat opened up. Water pump, outlet, sender and block temps were always hotter than the hoses by at least 10*. Dash gauge read 210* after 19 mins and when I shut it down the upper hose read 204, lower hose read 196 and the gauge was 210+ so it appears it's reading hotter than actual. I shut it down after 25 minutes as the temp gauge began to creep towards the yellow area. I ran out of time to do anything further but today I hope to check the timing. I'm actually relieved that it can idle for nearly a 1/2 hour without getting too hot; but then again it was from a "cold" start without any driving. I still don't know how this will perform in the real world. I'll find out this weekend.
My real interest is the manifold reading. After the engine reached temp, I adjusted the idle to 600-650 rpms at the dash tach. Anything lower and it's lopey; the tach bounces between 500-600 rpms. At 650 it evens out. When I disconnected the vac can from the manifold, rpms went up to 900. I wasn't expecting that. I readjusted the idle back to 650, connected the vac gauge. 14"-15" bouncing between. Still processing this but any input would be helpful.

 

Looks as if you have really attempted to address all the typical causes and still have the issue. Where was your car sold new? In a more moderate climate by chance? It could be a casting flaw with the block that has been there since the beginning of time. As you indicated in your initial post, you did not have the problem before you moved.

Did you think about just adding an electric fan unit in front of the radiator??? You cannot see it when you open the hood so the car still looks stock. Easy to install, dosen't damage any original components and can be easily removed. Mount the toggle switch under the dash and flip it on when in heavy hot traffic....

Many guys in my area who run their cars in heavy traffic have them and like them. Just a thought...

 

I have an AC car that can also run hot in slow traffic. Installed a dual electric fan and that did the trick for me! Took an hour to install...very easy. Good luck!!

 

L76- I'm from Upstate NY where the car was sold; literally a polar opposite from SW FL. As I said above, I think I've improved the temp issue somewhat but have yet to do timing analysis in an effort to eliminate that variable from the calculus. I tend to doubt there's a casting flaw as it would have been picked up when the engine was rebuilt. There were obvious faults in the system when I began this resolution. The fan clutch was toast, the water pump was leaking and the expansion tank cap wasn't holding 15 lbs. The coolant had low miles but it was 5 years old as was the stat. I addressed those and believe it's better but without tuning, I feel I'm not there yet. There's a lot of technical info on this forum by knowledgeable guys dedicated to peak performance. I'm working through these papers in an effort to learn what to do next. It takes time given everything else going on. Any additional input is appreciated.

 

64 air- Whose fan kit did you use?