71CutlassS455

Hi Guys,
I just bought a 1971 Cutlass S 455 .030 over with an automatic 3 speed trans, 373's in the rear and life is wonderful, unless I drive on the highway or for more than 35 minutes around town.

+ Highway speeds 55-60mph (3000RPM) i got up to 230 and likely got to my destination and shut it down. Scary!

+ Around town, light driving, 1st-2nd gear only, I'm fine until about 30-35minutes ingot he cruise and i start going over 210 steadily creeping to 215. So I bring her back as I'm afraid to do harm.

more specs,
-160stat
-Sum-38057 radiator
-electric fan with nice fitting full shroud - the shroud covers all but 1.5-2 inches on either side. I've always heard that covering the full radiator will restrict airflow on the highway.
-Car has the factor air dam - which really isn't an air dam so much as a piece of plastic that compartmentalizes the space behind the front bumper. Im curious is that flexible piece should sit free a few inches below the bumper OR as it sits now on my car which is inside the bumper, supported even, by the bumpers rear inner edge. A picture is probably worth 3 thousand words here.
-I have to check the timing - will do so soon but it runs great.


This is an AC car but i haven't used it. Also I should note there is an aftermarket transcoder in addition to the ac condensor in front of the radiator. Mini pusher fan on the trans cooler. Am I just blowing hot air and blocking fresh air?

Ive considered an aftermarket air dam from spoilersbyrandy.com which look well made I'm just not certain for this car that it will get air where it needs to go. Looks like it mounts just under the bumper and don't see how air gets past the plastic thats already there.

thoughts?!

Intragration

I don't like electric fans, some guys have good luck with them, but I know that a good mechanical fan with a clutch can cool a 455 just fine. The shroud should encompass the whole radiator, it worked fine for the factory. If this is an undersized fan, and it's only pulling on a portion of the radiator, that might explain a majority of your problem. Wasn't able to find the Summit radiator you mentioned, what are the specs on it? Have you checked to see if the condenser is clear? How do you actuate the fan? Automatic sensor, manual switch? Is the radiator pretty well flush against the core support?

If this was my car, here's what I'd do.

-Replace the electric fan with a factory fan, clutch, and shroud
-If this isn't an option, get the electric fan sized, set up, and running properly
-Make sure the radiator is clear internally and externally, and the condenser isn't blocked
-Make sure there's a spring in the lower hose
-Make sure the radiator is flush to the core support
-Make sure the air dam and other baffles are set up properly, they are there to direct air to the radiator, not familiar with how this body style was set up
-Switch to a 180 degree thermostat

This is what I would do. YMMV, and others may have different suggestions.

Fun71

I agree with the above.

Dude, let it shift into 3rd. With a 3.73 rearend it probably wants to do that at 25 MPH and you are unnecessarily keeping the RPM up.

toymobile

I have a 7 blade 1971 fan for sale in PARTS if you don't have one, By the way welcome to the site, lot of good people here with mostly good advice, Put your location in your avatar will help tell us where you are. Good luck, Johnny

71CutlassS455

Perhaps too direct of a statement on my part, I will put it in 3rd if ~25-30mph or above, but in Philly where I live there is a light or stop sign every 150ft. I was just trying to call out that I have been very light on the throttle and or overall speed when "around town."


WATER PUMP:
mil-16285
http://www.summitracing.com/parts/MIL-16285/

RADITAOR:
Sum-380457 is the correct #:
http://www.summitracing.com/parts/SUM-380457/
Radiator Style:Crossflow
Radiator Material:Aluminum
Radiator Finish:Natural
Overall Width (in):33.000 in.
Overall Height (in):18.375 in.
Overall Thickness (in):3.125 in.
Core Width (in):28.375 in.
Core Height (in):17.375 in.
Core Thickness (in):2.250 in.
Row Quantity:2
Transmission Cooler:Yes
Inlet Location:Upper driver side
Inlet Size:1 5/16 in.-1 1/2 in.
Outlet Location:Lower passenger side
Outlet Size:1 1/2 in.
Tube Size:1 in.

71CutlassS455

Thanks! Do you have the factory shroud too? I'm curious is the water pump I have on there now is the stock depth for proper fan placement. Didn't find the post, can you paste the link?

CutlassDad

2 cores upstream of the radiator will severely restrict airflow thru the 3 core deep area of the assembly.
The fan shroud has to be made (remade?) to cover the full width of the radiator core at the maximum depth possible. The open areas at the ends of the shroud can allow warmed downstream air to re-enter the radiator.

Intragration

The auxiliary trans cooler may be overkill, and is probably hurting your overall cooling cause. Everything looks decently put together, but there is a lot of stuff there interfering with airflow. If your cooling system was working properly, the in-radiator cooler should be sufficient for the trans. A seven blade fan might also be a bit much, but this may also be the correct fan for an AC car, not sure. If you get the fan from Toymobile and he doesn't have the clutch, these are available from numerous sources, including your local auto parts store. I would definitely recommend running a shroud, you may have to dig a little to find one, but my feeling is removing the external trans cooler and running a seven blade clutch fan without a shroud would be a passable temporary solution. Not ideal, but passable. See what others say. The lower baffle looks to be fine.

toymobile

Sorry don't have the shroud, I just BUMPED the fan to top of parts for sale. Thanks

71CutlassS455

Also, I just noticed the lower radiator hose does have the spring but only between the arrows in the pic. Should it go the full length? Where there is no spring i can easily pinch the hose closed. I don't recall a hose being that malleable especially if there is suction.

71CutlassS455

Without it the trans was on the brink of overheating. Now that runs cool and I track it with its own gauge. I just got the car and I guess I never test drove it long enough to see these things as an issue then, lesson learned.
But, It would seem like a proper cooling system should be able to handle the 461 and trans no problem. Sure the auxiliary trans cooler solved the trans heat issue but it is now be blocking the main rad, which is showing its true colors as being inefficient.

seems like there may be a few ways to fix this, just not sure which is the cheapest.

#1 install the original fan/shroud and hope the water pump i have on there is the correct depth.

#2 bigger radiator
#2a & better shroud covering the full surface area - possibly stronger fan.

#3 1&2


I really like the clean look of the efan though. and my biggest fear is the stock fan shroud wouldn't cover the aftermarket summit radiator the way it needs to.

oldcutlass

As the others said you have a serious airflow issue. The fan does not cool the engine once the car is moving airflow does. Your single fan and shroud does not allow enough air through and that big trans cooler is not helping. Then you have a fan in front also that deflects air.

71CutlassS455

so by removing the shroud and installing the factory shroud/clutch fan, the engine side of the radiator will not be as blocked up and allow more air to flow though...sorry i can be dense at times.

does anyone feel that simply making that change will negate the need to remove/relocate the trans cooler?

RetroRanger

have you verified the fans are turning the right way ?

71CutlassS455

yeah its a puller fan

Koda

The ones I have made to replace go the whole way.

71CutlassS455

can you send me the part number? i haven't seem any with a full description telling me it goes the full way,

BlackGold

Let's not forget that the flip side of a cooling system not having enough capacity is an engine which produces more heat than the cooling system can handle. I'm just saying that it's possible his cooling system is working fine but his state of tune is off -- carburetion, ignition, or both. It's also possible the engine was built with too tight of clearances.

oldcutlass

I assure you that is not his problem, I've seen big blocks run on a 1in thick aluminum cheapie radiator with plastic tanks, no shroud, and a flex fan with no issues while cruising.

Intragration

What temperature was the trans running at when you say it was on the verge of overheating? Transmissions don't typically overheat, unless there's a problem, unless you're putting them under tremendous stress, or unless the cooling system (e.g. the in-radiator cooler) isn't working properly. Are you towing with the car? IMO, unless you NEED an auxiliary cooler, it's a gimmick. It's blocking the radiator, it's a potential source of leaks, it's adding weight, and it's completely unnecessary.

If you just really like it, I suppose the remainder of the cooling system should be able to compensate if it's working properly. But then there's the possibility of over-cooling the trans, which is totally avoidable. If the external cooler is important to you to keep, just make sure you're going through that first, and then the in-radiator cooler, to warm it up again.

How many miles on your engine and trans?

71CutlassS455

So I've only have the car for a few days and not even a tank of gas yet. Trans temp 150-160.

There is zero space between the three cores, none. I was suspect that is a big no no. Was the a/c condenser suctioned to the radiator from the factory? I would think that just getting some space between the three would provide some benefit.

Ordered the following:

Factory fan shroud
Thermostatic fan clutch
7 blade fan
New lower hose and spring


Also this car has the flat hood, no lovers or scoops. The heat really has nowhere to go once in the engine bay. Any way to improve general heat escape?

Intragration

150-160 trans temps were at overheating, or now? That's a pretty great trans temp. Don't worry about the no louvers, there is no possibility of your engine compartment overheating unless it bursts into flames, and then you have bigger problems. Sounds like you are well on your way to having the problem fixed.

What is the mileage on the engine again? If this is a zero mile motor, you will still be generating a lot of heat for a while. Take it easy on it, let it cool down, and you'll get it broken in just fine. And don't forget to change the oil as recommended and use something like Valvoline VR1 that has plenty of ZDDP. This is important, you might want to do a search and find out more about this if you're not already familiar with it.

rustyroger

Is there an elephant in the room in the form of a choked radiator?.
If the radiator is old it make be internally plugged but look fine peering down the filler neck.
I have cleared out radiators with domestic descalers with moderate success, but several cars I've owned have needed a recored radiator for a long term peace of mind cure.

Roger.

71CutlassS455

Possibly 170 at most now - but was told it would climb past 200-210 before the cooler was installed.


Motor is 6 years old but low miles, few thousand


Great point of the ZDDP, was aware from my Pontiac days but never hurts to bring it up.


The radiator is also 6 years old - could it clog in such a short time? I'm sure its possible, but likely?

hookem horns

Agree since happening on the highway. Or restricted coolant flow, like a collapsed hose or bad water pump. BTW - An old trick if stuck in traffic is to crank up the heater until you can pull over.

rustyroger

If the radiator was left empty or without an antifreeze mix for a long time it's possible for corrosion to build up on the inside, affecting it's ability to transfer heat. But I do think it unlikely in your case. If the cooling system had a leak and was frequently topped up with hard water (high calcium content, an issue where I live with a chalk subsoil), it can build up limescale in the tubes.
But you appear to have troubles cruising the highway, which points to the radiator being unable to cope, maybe it's partially plugged, maybe it's too small. Hard to diagnose from afar!.

Roger.

DewChugr

You might try some Windstar fans. 4403.157 cfm total. They says fits like a glove and looks nearly factory. This thread on ls1tech shows the dimensions and photos. I got one from a yard for ten buck and 2 for the Volvo relay.

71CutlassS455

that makes sense rustyroger. Well I'm just going to slowly track the issue down, starting by bringing it back to stock with the stock fan and shroud. All the parts came in today but the fan itself. should be her next week.

Related Question: The new shroud covers all the fins nicely but because the radiator is not stock the should is off center and can not mount to the upper rad support plate. and the fan will mostlikly not fit in the shroud correctly. I could do a hack job and bend this, tweak that to make it work but i might swell get the true replacement radiator. haven't fond it but do you guys know the exact radiator i should get to just drop it in? aluminum great but doesn't have to be.

Fun71

Here's something to think about:

A friend of mine recently went on a several day camping/fishing trip and while he was there everything was OK, but on the way back into town his truck started running REALLY hot at highway speeds. Couldn't find anything wrong with the cooling system, then after talking it over at work he found a mouse/rat nest between the radiator and AC condenser. Pulled it (and the cooked babies) out and everything was back to normal. The nest was maybe 5-6" diameter and that was enough to block the airflow and cause overheating.

cjsdad

Your radiator, condensor, and trans cooler need space between them. The fins can actually block the next heat exchanger if they are too close together. They need at least a quarter inch so the air can pass cleanly through the fins. Then you need to have a foam seal between them so the air can be pulled through them by the fan. The fan and shroud you have currently is not too bad for sitting still, it draws air through about 80~85% of the radiator, but for cruising it limits airflow to only the area where the fan opening is. Looks about 45~50%. Your electric fan may pull like a hurricane but the shroud is to short and blocky to let air flow through it. I have seen shrouds like that with rubber flaps that prevent air from pulling back through by the fan but they open up and let more air through when driving. The factory shroud and clutch fan will utilize the entire radiator whether driving or sitting still.

Use the factory shroud
Use two smaller electric fans or one HUGE one, or a clutch fan.
Separate the heat exchangers and seal them with foam.
Seal the radiator to the core support with the same foam. (Radiator sealant foam tape, not urethane foam from Home Depot!)

You want ALL the air that comes through the grill to flow through the radiator!

Railguy

I had a cooling problem.semed everything I did, did nothing. It always ran about 210.
I was messing around with the valve geometry and couldn't get it right. So.l had to take the head's off and mill the part where the rockers bolt on.when I put it back together no over heating problem. I also changed the thermostat and the rad cap which I had changed before.
I've always wondered if it was the valve geometry that was causing it. I never could get an answer from anyone eat her way.
If you get a chance check the valve geometry.
Railguy

71CutlassS455

I pray i don't have to get that far into this solution. Just spent a good amount of coin on the car and now a buck and a quarter on the cooling system retooling. I feel pretty good about the possibility of the factor fan, shroud, proper spring in the lower hose, and spacing between the cores fixing my issue. I think there is a 160 stat in there too so i got a 185 or 195.

take a looksie...

midrange

I had cooling issues several years ago when I bought my car.
My thread here may give you another area to look into.https://classicoldsmobile.com/forums...ter-temps.html

The pump I removed had an impeller almost exactly like the one in the left pic below.
The pump I installed, and seemed to fix my problem, had an impeller like the right pic.

71CutlassS455

good thought but i was able to find some decent pics of the pump i have on there here, https://classicoldsmobile.com/forums...step-step.html

looks like a quality impeller setup.

71CutlassS455

Update: Got the fan in the mail today, slapped it on without the shroud (see below) and took it out for a ride. after 30minutes driving it harder then i have so far it struggled to get past 185! When i put it in the garage and sat i finally heard the fan engage around 200 and it didn't drop bit it also didn't raise much. I sure the shroud would help tremendously standing still. Shocked at how small the factory fan is, barely notice it in the engine bay.

There has to to be gobs of air flowing through the radiator now without that restrictive efan and generic shroud.

Now on the the shroud issue:
With the aftermarket summit radiator the shroud sits about 2 inches too high and half an inch to the right of center. I couldn't install the fan with it. I think this is fixed by placing some type of spacer between the shroud and the radiator top plate (whoa the name eludes me ATM)

Wish i just had the stock radiator or an EXACT aluminum replacement. Can you guys point me in the right direction?

oldcutlass

You need to fab some brackets to mount the shroud. The fan has nothing to do with cooling while driving at speed its strictly a low speed and idle supplement.

toymobile

Glad you got the fan OK, the fan blades need to sit 1/2 way inside the shroud that should cure all your heating problems. Good luck, Johnny

BlackGold

I've never understood this advice. The factory put the fan much deeper into the shroud. As long as the fan isn't too close to the radiator, it'll suck more (that's good) if it's deeper in the shroud.