Well 396 Rat the slow flow concept is not dead yet but it weakens everyday. My thinking is the longer it stays in the radiator the more it cools and the longer it stays in the engine the more it heats. Now since a radiator only drops the water 6-10 º on a pass through it you want the water going in to be only to be only slightly hotter than what comes out. And the way to keep the differencial small is to have fast flow. The faster flow also creates turbulance in the water to remove the boundry layer of cooler water on the inside surface of the tubes.
I first read about the small drop in top to bottom about 45 years ago when design technology was giving only a 4-6º drop. It seemed to fit with such a small drop each pass you wanted a lot of passes through rather than a few.
I have found the sites of EMP Stewart, Fluidyne and crracing to be great places of cooling system insight.
Based on what these cooling system companies think we have a C&R radiator in a 406 inch road course car that on a 105º day runs under 160 w/o a thermostat. We run a 195º as that gets the water and oil temps where we want. Oil cooler is intergal to radiator. Mel


[Modified by Mel Foye, 8:39 AM 7/1/2003]

 

"406 inch road course car that on a 105º day runs under 160 w/o a thermostat. We run a 195º as that gets the water and oil temps where we want."

No Mel! For Gods sake! put it back in! It cant run cooler without one installed!! Dont you know anything! Your going to gernade your engine!
It must have been 260! Not 160, as the water would not have time to cool!
Its better keeping more hot water in the block, and let the water in the rad have time to cool! Whats wrong with you! you are not walking in the right direction in the circle! Save your self! Go the other way! :lol:

 

Whoa... Easy guys.... Again thanks for the inputs so far. I didn't have time to try anything yesterday, but should be able to do some experimentation this afternoon. I'll keep everyone posted.

 

i have a pressure gauge hooked to the intake water jacket.
even before it is warmed up, it gets 7-14 psi in the engine. i haven't removed the 'stat, but i expect it would not pressurize so fast without one. A pressurized block will have less steam pockets around the exhaust valves.
Just some chat unrelated to subfixers problem. :lurk:

 

Highway speed heating is a different animal than heating in slow traffic; assuming the obvious parts of the cooling system are functioning (thermostat, lower hose not collapsing, fan belt not slipping, etc.), highway speed heating is usually a symptom of a radiator that won't cut it any more (even though it "looks good" or "flow-tests OK" - neither of those says anything about its heat transfer capability, which is all that counts); another less likely cause is a blown head gasket. The thermostat is also a designed calibrated restriction which works with the water pump to establish the proper coolant flow rate through the system (this stuff didn't happen by accident - engineers spent a LOT of test time developing the cooling system). I think one of Tom's radiators and a 180* Robertshaw balanced-flow #330-180 thermostat (also sold under the Mr. Gasket name, made by Robertshaw) will solve your problem. The coolant carries heat to the radiator, which transfers it to the air (and airflow isn't an issue at highway speed, as it can be in slow traffic); if the coolant carries heat to the radiator faster than the radiator can transfer it to the air, you've got a highway heating problem. Been through this umpteen times over the last 40 years, and it's almost ALWAYS the radiator that's at fault, especially if it's "original" or has been replaced with a different radiator with less heat transfer capability; radiators are the wrong place to save money - the original radiator had 4600 BTU/min heat rejection capability for a reason. Replace it with a lesser radiator, and you can expect problems. :thumbs:

 

:iagree: John. Nothing fancy and should fix most problems. :D

 

lots of good points John.
One weak one is suggesting that an old rad can't cool cruising at 70mph. i seem to remember reading that 70mph requires less than 55 HP.i forget the details, but it is certainly NOT anywhere near max capacity.
if somebody was climbing a steep hill WOT @70 and it overheated i would look very carefully at the rad. But level cruising? NO WAY
subfixer is most likely being faked out by a sly clutch that is out to get him. :D

 

Hey Subfixer,
Just a few thoughts here. Did you check the gap on your plugs?
Also check the operating temperature with an infrared thermometer to
verify that the actual operating temperature is the same as what your
temp gauge is reading. This could be a calibration issue. I put a new sensor
on my '62 and kept getting high readings, BUT the car never did boil over.
when I checked it with the infrared thermometer, the gauge was wrong.
I corrected the gauge by adding a resistor in series with the sensor to
render the correct operating temperature on the gauge. And YES it will
still indicate if the car overheats. this just centers the operating temperature
for a correct reading.
Good Luck!
Take Care,
Shawn :chevy

 

The fan clutch has absolutely nothing to do with highway-speed cooling; at 70mph, the ambient ram-air flow through the radiator (cubic feet per minute) is FAR more than any fan could ever generate. The fan clutch is frequently the culprit in slow traffic, but not at highway speed; thermo-modulated fan clutches are designed to disengage over 3000 rpm anyway. Assuming coolant is flowing, only two things matter for cooling - heat transfer capability and airflow; at highway speed, airflow (CFM) isn't an issue unless there's crud in front of the radiator - all that matters at that point is heat rejection capability (BTU/min) of the radiator. Heat goes into the radiator, and if it doesn't get transferred from the tubes/plates and fins to the air, the temp gauge goes up until the heat input goes down. :thumbs:

 

John
do you know what cavitation is?
i guess not.
if subfixers fan is blocking the flow, it will run cooler without it. i'm not sure if it is the fan or the clutch; most likely a failing clutch.
and of course i could be wrong, as could anyone else here. But the topic is entertaining, it is a slow week for me! maybe he has a dead rat in there. LOL

 

OK, I quit, I know what works for me and my customers and thats what matters. :D :party:

 

"I know what works for me and my customers "

Oh, Whats that? I must have missed it in your posts?

 

would you like to become a customer? :)

 

:lol: :blueangel: :lol: :lolg:

 

Update..... Yesterday I got around to checking some more stuff. I topped off the coolant above 1/2 full in the tank. Just about filled to the top. Then I went for a ride. Now it get's weird. I could watch the temp gauge go up to about 175-180*, then it was obvious that the thermostat opened because it dropped back down to about 160*. And it stayed there for the first 15 miles or so while driving on rural roads. I got on the highway and did another 12 miles at 70 mph and the temp never got above 180*. I stopped at a store and when I came out, the temp was about 210* due to heat soak, but went right back down to 170*.
The only difference between yesterday and last Friday when it was running around 210-220* was the outside air temp. Last Friday was in the upper 80's and yesterday was in the lower 80's.
Another question I have is how much clearance should there be between the fan blades and the shroud? Mine seems to have more than it should and I'm wondering if the wrong fan (diameter) is installed. I have about 2" clearance all the way around. I seem to remember that for the most efficient operation of the fan, there should have as little clearance as possible between the blades and the shroud.
Any thoughts? Thanks.

[Modified by Subfixer, 8:35 AM 7/2/2003]


[Modified by Subfixer, 8:37 AM 7/2/2003]

 

i don't see anything strange. i've owned 50+ old cars and the only time they run hot is if they are low on water. Now check the tank cold and it should be 1/2 to 2/3 full(i assume it is mounted higher than the engine). i love low cost cures; doesn't get any cheaper than some water! :cheers:
PS you might want to install a coolant recovery tank; all the new cars have them, i have added them to mine, that way if they puke some water on a hot soak, thy can suck it back in so they won't run low as quick :yesnod:

 

Your fan should be 17 1/8" diameter. Clearance,blade-to-shroud about 1". In profile view, fan should be abouy 1/2 in and 1/2 out of shroud. If you have large gaps between the rad and the shroud because or the replacement rad, you're gonna lose a lot of airflow thru those gaps. Be sure to close them if they exist.

Joe :thumbs:

 

Been there and done that.

I have tried all of the above, and it still ran hot with the a/c on in town.

I know that it is not proper or NCRS approved, and will deduct points if you are into that, but I got a SPAL push fan from Dewitt. Problem solved. The car will idle below 210 all day long. Just took it round trip to Bowling Green, Nashville and back. Worst it ever did was just a smig over 210 while cruising at 75 on the hottest day of the trip.

If you are in to correctness, you could always take the fan off when doing shows.

I've have been fighting this for over a year, and am delighted with the results.

Oh, while I was in Nashville, my wife bought the midyear buyers guide. After thumbing through it, she pointed out where it said that 65-67's were notorious for running hot.

Again, it may not be correct, but for my semi correct driver, the problem is solved.

 

The current coolant level in the tank is almost to the top cold. Hasn't puked yet.
Thanks for the fan measurement. In profile it's in the correct place, just wasn't sure about the diameter. I'll check mine this afternoon. Rad/shroud are all sealed up with the C/B radiator (that was the first thing I did when I installed it; certainly doesn't fit like the correct one).
Looked at the pusher fan, but I really don't want to go that route yet. Don't have A/C either so at least I don't have to worry about that.

 

i want to thank you for your reports. :cheers:
I've added the recovery tank to my web site and made it #2. While i've run them for years, i forgot it on my site.
I'm surprised the expansion tank is full cold, where could it expand to when hot?
Will you put a recovery tank on? :cheers:
(a proper fan is a good idea too)