now that my car will handle well at 75-80mph I tend to do that. and I'm sure the motor is buzzing at 3k + to do so. the temp which around town is 180 flat. is climbing towards 200. Stock 4 speed drive train. any suggestions to cool her down at speed. water pump is new so is 180 thermo. fan shroud? elec fan? taller tires? what do you guys think.
thanks

_________________
64' Valiant Signet 5.9, 64' Dart 170 moredoor 3.7, 67' A100 3.7, 00' Dakota SLT 4.7

Shouldn't exceed 195, have you flushed the radiator and cooling system? Is the heater core plugged?

If all that is good, next up might be a better fan for HD cooling or better radiator.

-D.Idiot

200° is fine as long as it doesn't keep climbing. I would make sure the radiator in clean for starters. I would also recommend a coolant overflow bottle/tank/reservoir that will allow you to completely fill the radiator without loosing coolant onto the ground and eliminate air in the cooling system. Air reduces cooling system efficiency and can cause increased water pump cavitation.

_________________
Joshua

First, make sure your system is working as designed. Is a hose collapsing at higher rpms?
How good is your radiator? Good core? Look into a larger radiator, with modifications to the bodywork to ensure airflow through the whole surface of the radiator. Some of the better aluminum radiators cool much better than the original brass units.
A fan shroud is designed to improve the fan's efficiency at lower speeds, but can restrict airflow through the radiator at highway speed. Some performance cars have flaps on the shroud to let more air through at higher speeds.
The fan does less useful work the faster you go, but uses more power at higher rpms. An electric fan that does not block airflow through the radiator wouldn't hurt. With a proper thermostat setting, it won't be running at speed, and won't be eating up the horsepower - and causing the engine to make that extra heat - that an engine-driven fan will.
You could install an external oil cooler, if you have a place for it.

_________________
"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

radiator was flushed out awhile back. dont know about the heater core though. I could drive all day under 60mph and it would sit at 180. it seems like keeping a sustained load on the engine while it's in the powerband is too much for the cooling system. I'll look into a bigger radiator and overflow. when its around 200 and I slow to 60 it cools back down to 180 pretty quick. 205 is where I would start to freak out.

_________________
64' Valiant Signet 5.9, 64' Dart 170 moredoor 3.7, 67' A100 3.7, 00' Dakota SLT 4.7

High speed heatup is a water flow/heat rejection problem. Radiator too small and/or not taking enough heat off the coolant. Find a good, competent radiator man to put a 3-row high-efficiency core in your radiator; these reject a lot more heat. Use the correct 14-pound cap, preferably the correct partial-pressure type. Use the correct 180° thermostat, not the 195° unit most of today's parts books claim is correct. Make sure the radiator fan is installed right way round.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

The stock radiator is large enough if it's in perfect condition. I drove a fleet of those cars when new (1960s) at those speeds, never a problem.
Either your radiator needs to be rodded or re-cored, or your block should be boiled out, or both.
I'd put in a bigger core.
As SlantSixDan says, it's a water problem not an air problem.

Best fan for 80 mph?

None at all.

I have a friend in Jacksonville Florida (hardly the artic circle) with a V8 Thunderbird with NO fan, and it only runs hot in slow traffic. Anthing above 35 mph and the fan is just wasting power and making noise.
If you have a car with an electric fan and it goes on at highway speed something is wrong with your water system.

_________________

I'm going to do the radiator, but first some product testing. I'm going to flush out the system and run redline water wetter and water. just to see if there is a difference. no freezing danger where I live.

_________________
64' Valiant Signet 5.9, 64' Dart 170 moredoor 3.7, 67' A100 3.7, 00' Dakota SLT 4.7

I was going to suggest running less antifreeze (~33%) so there's more water in the system to take the heat...

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

At higher speeds you can also get into an airflow situation where the air flows around the grille instead of through it. Tie a piece of wool to the grille and have somebody observe its action at 75mph.

(I use powder snow in the winter to observe aerodynamic behaviour....another thread)

As Panic noted a fan is just for in town. I dont run a fan on the Valaint even in 90 degree weather climbing 10% grades,,,,,,I just have to be sure to maintain at least 50mph.

_________________
Yeah....Im the one who destroyed this rare, vintage automobile.....

Definitely block any openings etc. around grill, support etc. to make air go through the core. Sometimes the car has been apart and not re-assembled with all the right bits in order, and the rad or ? has moved down or back creating a gap. Some old inner tube makes a nice seal here, can be easily pop-rivetted onto the closest sheet metal, costs nothing, weighs nothing. remember to examine the area under the bumper as well.
If you were sure the car would never slow down, you could get some free mph and gas mileage by closing off some of the grill area. Remember the Charger Daytona? It didn't overheat because the grill was too small, it overheated because it wasn't driven fast enough!

_________________

I was having this same exact problem a few months back. Turned out to be the lower rad hose was sucking closed at highway speeds. I pulled the coil out of another hose I had laying around and put it in. Fixed my highway overheating.

_________________
1974 Dodge Dart Custom, 225, 904, now with a Holley 2300...

That is an excellent idea. Thanks for giving me a project this weekend!

I agree with having your existing radiator looked at. I used to run a little (for my heavy car) 19" unit that cooled just fine at high speeds (maybe my clutch fan helped, who knows). The only reason I put a 22" in was because it was cheap ($60 at a wrecking yard) and still new.

Agreed on everything EXCEPT what you worte in that linked post about radiator caps.

I've mentioned before that I still have the OEM radiator cap for my '73 Plymouth (318, non-recovery radiator system). It has the spring-loaded center valve, not the weighted "partial pressure" valve. I never even *saw* a "partial pressure" radiator cap until well into the 80s, so I disagree that Chrysler ever used them on non-recovery systems (and maybe not on recovery systems, either in the 50s, 60s, and 70s.

I can tell you from multiple experiences (mine and other peoples') that running a "partial pressure" radiator cap on a non-recovery radiator system is an invitation to a boilover. At a MINIMUM, you'll wind up with a car that "burps" coolant after you shut it down. Since non-recovery radiator systems have a cushion of air in the top radiator tank, there's no water flow out the little hanging valve to force it closed until the cooling system is at a raging boil, and by then its too late. You MUST run a spring-loaded type cap to ever properly build pressure and suppress boiling in a non-recovery system. A recovery system, frankly, works just fine with either type of cap and I think it was stupid to ever even produce the caps with the hanging valve. In a recovery type system, the fact that the radiator is 100% full of water means that as the water starts to expand, WATER is rushing by the little valve and will draw it closed with or without the spring. The air slug in the top of a non-recovery radiator will never, ever do that without the aid of the spring.

_________________

Disagree all you like, but the original cap on my '62 was partial-pressure, and the FSMs in the '60s-'70s-'80s-'90s all carefully describe the free-hanging valve. Here's what the 1976 FSM has to say on page 7-8:

"The vent valve at the bottom of the cap should hang freely. If the rubber gasket has swollen and prevents the valve from hanging loosely, replace the cap. Hold cap in hand upside down. If any light can be seen between vent valve and rubber gasket replace cap. Do not use a repacement cap without this vent valve that hangs freely." (boldface is theirs).

And here's from the 1963 FSM on page 7-7:

"The brass vent valve at the bottom of the cap should hang freely. If the rubber gasket has swollen and prevents the vent valve from hanging loosely, the cap should be replaced." (same text in '64, '65, '67, almost identical in '68 and '71).

And here's from the 1992 FSM on page 7-19:

"Hold the cap in hand, right side up. The vent valve at the bottom of the cap should open. If the rubber gasket has swollen and prevents the valve from opening, replace the cap. Do not use a replacement cap that has a spring to hold the vent shut." (boldface is theirs)
My experience doesn't agree...and apparently neither did Chrysler's, 'cause they specified partial-pressure caps right up til recently. Donno what you found on your '73, but what should've been there was a 2998 982 (without coolant recovery) or a 3673 891 (with coolant recovery) per the '73 FPC.
Chrysler just really doesn't seem to agree with you on this, and I've never had any boiling/burping problems running the specified cap type (free-hanging valve) on non-recovery systems. What am I doing "wrong"? I've run full-pressure caps on non-recovery systems and had no problems except added stress on the radiator tank solder joints, which I don't like to do to the comparatively fragile round-top radiator tanks. Come to think of it, I don't like to do it to the "one strike and yer out" plastic-tank radiators on my '90s Mopars, either!

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.