Hot Rods SBC overheating...yes I've tried almost everything!

the hotter the motor the more efficent it is and the better the oil lasts in it as it helps to boil off any condensation that forms and creates acids , a 160 is good if you race it

 

It's not uncommon for the temp to creep up when at an idle. With the car sitting still, even with a good fan/shroud, often times there just isn't enough air movement through the radiator to dissipate all of the heat. Besides that, that water pump is also turning slower which reduces water flow rate thru the engine/radiator, reducing heat transfer rate. So this alone is not so unusual. Many cars that run fine once moving will run hot at an idle. Ask any big block Chevelle SS396/454 owner. Heavy traffic really sucks!

Yes, thermostats are not real highly developed, highly specific pieces of machinery. They can be slow to open, especially the first time the engine comes up to temp, then once opened they will work fine and manage the temperature control normally. As other people have already mentioned in this thread, some thermostats, even brand new, just will not open correctly, and lot's of guys have replaced them mutliple times to get one that operates correctly. 31Vicky mentioned how to test the operation by putting the t-stat in a pot of water on the stove and monitor the temperature of the water with a cooking thermometer or another gauge or an infrared gun, and see what temp it opens at. People have learned to do these things because problems with thermostats are so common.

Put the right mechanical fan on it and ditch the electrical fan. Not only do they look like crap, they are not as efficient as a mechanical fan.

If the filler neck sits directly over the top tank you should be able to see movement of the coolant when ever you goose the throttle. As you increase the engine speed the coolant will flow faster and this should be visible in the top tank.

Best thing to do though, with all the issues you're having is to get an inexpensive infrared gun and measure the temperature difference between the top and bottom tank. If there is no difference, than the radiator is not shedding heat properly.

 

Cfm, the dual unit on my truck is around 5500 but I have a 7.4 vortech and tow with it , a factory car unit should work well ( we have used 4th gen firebird ones with very good luck )

 

Haha, but at some point it starts to cook the oil!!

I do think a 160 thermostat is too low, it is beneficial to get the engine up to 190 - 210 degrees operating temperature. Water boils at 212 at sea level, but will start to volatize below that point, so condensation in the oil will evaporate off. Additional heat on the oil will drive oxidation. Rule of thumb says that for every 10*f the rate of oxidation of the oil doubles, shortening the life of the oil. There is a balance there between getting it hot enough to volatize the condensation but low enough not to drive oxidation.

 

i did actually read the entire post and responses before posting the first time. (ok, skimmed over, but close enough).

And while i believe the fan situation is indeed incorrect, is a potential concern, and needs to be corrected immediately, i will still go out on a limb and remain unconvinced that it is the problem.

If there even is a "problem"-----is the car truly overheating? Or is it merely emptying into the overflow can---which is a normal action for radiators.

Not afraid to have egg on my face here.
However, i contend that 205 -210 degrees, while a concern, is still acceptable AND the force of the air running through the radiator while the car is moving at speed(esp. 35mph and above) would overpower the air being generated by the fan.

2) the elec fan, being closer to the rad than the belt driven fan would/should suck out enough air to cool the radiator at idle.

3) The gauge still has not been tested, thus all the above data may be b.s.----the car may be running just fine temperature wise.

(note: i have no idea what the f i'm talking about.....)

 

Well I read and I just seen 15 pages of answers and figure by the 5th page and still going on. I just put my input in. Like I say I don't have room to speak. Just ideas and inputs. So I threw it out there. Because we all go thru mistakes. And over see the simplest stuff. Op had it going till 15 pages.

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I drove the panel 10-12 miles today around town to see how it would act. Remember, I have only removed the mechanical fan thus far and the electric fan is still mounted, though it's only pulling 1700 CFM and I really don't think it's doing anything at idle to help. So I'm going to be ordering a reverse rotation mechanical fan and ditching the electric fan.

The temperature hand never got above 165* while driving. It creeped up to about 170-175 at red lights or a series of stop signs. Granted the temperature today was in the low 60s and I don't have any type of functional fan, I wanted to see how it would perform. If I had driven it in these temps last week, I would've been around 230* by the time I got home driving the same distance.

Now, before you ground me (haha!) I know 160-165* is not an optimal performance temperature. I'm going to wait until the temp goes back up here in KY and drive it a few more days to make sure everything stays the way it is. If it does, it looks like I will need to swap back to a 180* or 195* thermostat as 160* is too cool. Honestly, right now I'm just glad to see my gauge didn't cross 200*.

I have still yet to 100% verify the accuracy of my gauge, and trust me I will be doing this in the next couple of days as well as adding a mechanical fan. It seems from opinions I can't go wrong with a steel or flex fan so I'll order one from Summit or Amazon tomorrow and hopefully have it here by the weekend.

From this driving experiment, it seems all of my troubles have been airflow related (idiot like myself installing the wrong fan) and not a coolant flow problem.

I would have never have gotten to the bottom of this without you guys. I honestly can't thank you enough. I will keep you guys updated as I get the mechanical fan mounted and let you know how it does in warmer temps, but I can ensure you things are 99% better already


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Ok sound good. I installed my motor without mechanical fan and put electric. I have plenty of room for mechanical but I did it for performance and mpgs. But honestly I bought a 6 blade mechanical fan from summit the steel one. And man day and night difference for the cooling I'll tell ya. Electric just doesn't cut it for me it's used as a puller as I try to hide it so it not seen from the front thru the grille. I may remove it but since summer is coming I'll see how it goes with Cali traffic. But nothing wrong with mechanical. Unless your racing I guess. Also I do have my original 4 blade steel fan but the temp was holding about 10 degree hotter. Bit here a pic. Of what I'm currently messing with and no shroud and no overflow. I have these items haven't had time to put em in

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After going threw a bunch of "new junk" thermostats I bought a Milodon High Flow with the balance sleeve. Every one tested great, worked great. It alone dropped the temp on a BBC Blown Willys from 225 ( and climbing) to a steady 210 in traffic.........................................................
Sounds like the OP is getting things under control.

 

Wow, 16 pages and no one has suggested flow testing a unknown 'swap meet' rad???
The motor was running fine before the transplant.
Even doing it in place, drop your hoses, cap the bottom, fill it full of water, remove the cap...
Does the water trickle out or gush out?
That would have been my first move.
Good luck, Aaron.

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I'm missing 10 pages here.

 

You guys think I will be okay running this fan?

https://m.summitracing.com/parts/de...ing-products&gclid=CKKF29el0dMCFQcOaQodYWIMqw


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Absolutely not. Flex fans flatten out. Go with a steel fan.

 

X2^^^. Lots of factory stuff works for a very good reason. They spent millions of $$$$ designing mundane things like fans to make sure they work. Keep it simple and you will be out of the woods a lot sooner. And temperature creep at idle is normal. IT's not time to get paranoid (yet).

 

I' be run a flex fan for over a 100k miles on my old rod. Worked very well. At low rpm, in traffic, the blades have a lot of pitch, as in the photo, to draw a lot of air through the rad. At faster speeds, more air flow, more rpm, it flattens out to reduce drag on the engine. The best of both worlds.
On the other hand, you can't go wrong with the factory type fan

Phil

 

Well fellas, I've opted to go with a higher CFM electric fan as opposed to a mechanical. As one of the above posts had suggested (and I didn't notice) the mechanical fan did not line up properly to the radiator and I have no room for a water pump riser.

I drove the panel today and it ran between 165-175* during normal and highway driving. When idling or sitting at a red light, the temp would rise to around 205-210* with no fan use, and would slowly fall back down when I would kick on the electric fan.

So, I have two quick questions.

1) Is a 35* rise in temp normal under idling?

2) How quickly should my electric fan be lowering the temp at idle?

Thanks guys.


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With no airflow? Yes, that's not at all out of line. It sounds like you need a good cfm fan, and I would not wait to throw in a 195* thermostat. From your reports it appears your problems were airflow related, which is good. I have no idea what that engine compartment looks like, but...you may look for simple ways to vent hot underhood air also.

 

The engine bay is basically a coffin. Huge inner fenders, motor tucked tight between frame rails, not much air can flow. It's basically an oven with an engine inside. Lol. But I agree, I believe the air flow was the problem. I can turn on my electric fan and the temp will slowly fall, I'm just not sure if it is dropping quick enough.


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A fan with sufficient CFM should make a big difference. They have fan thermal switches available that very easily install in radiator hose- sometimes they are included in fan kit.
If you are switching it manually, I'd recommend that you turn the fan on anytime you are not moving, or even driving slowly- don't wait for temp to rise before switching on fan.
Maybe take a hard look at inner fenders and see if you can create some vents towards rear of engine bay without creating other problems.

 

Louver the hood!!! Heat rises, louvers are there on top. Release heat, look coooool. That's what louvers do.

C'mon, guys...Give me a beat. Two-four time, Louver song...

 

Reread page two of this thread where I suggested replacing the radiator. That used Griffin was sold in a swap meet for a reason.

 

That's what louvers doooooooo....

 

I would love to. Don't know if anyone around here that does it though.


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Have Needlouvers? mail you some louvers. They don't take up much room. He could probably fit a couple hundred in an envelope.

 

Never heard of this?


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Keep it simple. Start with the fan and thermostat upgrade and see what happens. If the electric fan lowers idle temp to near thermostat rating, consider the job finished.

Also note, when it gets hot and humid, it will be harder to maintain water temp, so keep an eye on it.

Phil

 

It's supposed to do that. As the coolent heats up, it expands. The overflow tank is there to catch the extra and to allow it to be sucked back in when it cools and shrinks.

Go back to the higher pressure cap, that raises the boiling point of the liquid. Rig up something as an overflow tank. See if that doesn't solve it for you.



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That sounds fine. I did a ~75 mile rod run last year with no fan at all (SBC in a 37 Chevy, electric puller fan) due to a wiring mistake. Ran fine, as long as I kept moving.


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