Over Heating

[cjmccall]

Have any of you other Hot Rod owners having any overheating or running very hot problems?? My #235 SBC, 700R4 air conditioned hot rod runs 200 plus degrees traveling down the highway and 220 plus is slow or stop and go traffic. This is with a 160 degree thermostat, a 3600 CFM fan, high flow water pump and side panels cut out with grills to let out the hot air. This is with air tempertures of 85 to 95 degrees.
This engine has run hot since day one. I have 3800 miles and it seems to be getting worse.

[tirod]

Taking the 200 temp at face value, it's about normal. 220 in the drive thru, ok. With a 15-16 pound cap, it won't start boiling until 225.

This makes a good case about the thermostat - it cannot make an engine run cooler. All it does is open at its set temperature and allow coolant thru. The cooling ability of the radiator to be better than the engine heating up, is what makes the system work. For example, race cars using the same parts won't have a t-stat, they run a plate with a hole in it sized to let the system work. At 7,000 rpm and 200mph, it's usually not an issue.

Two areas not mentioned so far - the number of cores in the radiator, and how well the fan shroud fits to control air and make that path the one of least resistance. I suspect the radiator is big enough, what might likely be happening is air is simply going around the core because there's not enough shroud to limit it's shortcutting. It has to completely enclose the perimeter of the core and extend a half inch past the blade tips.

There's another area of potential concern - high flow water pumps can actually be detrimental. If the flow is too high, it doesn't sit in the engine block or radiator core long enough to transfer heat. That's becoming a common complaint. It takes some "dwell" time for coolant in contact with a surface to transfer heat. Going back to the race car, it's another reason they use a plate - to control the amount of flow and pace it at the optimum rate of heat transfer - not the highest gallons per minute they can get.

The system is working, getting it a bit cooler would be ok, but factory cars run at about 200 degrees, too. That's not considered overheating in them. My gauge is marked at 210 top dead center, it's red from 230 up.

[ksuhre]

I'm not having an overheating issue like my good friend Chuck, but it was great to read such a thorough response from tirod! I don't know what Chuck will find with his issue, but I would not have thought about too much flow, always learning something new, thanks to the great folks on this forum!

[450dude]

actually a thermostat can have alot to do with how cool your engine runs. i have done many cars. your always trying to get it so that your thermostat is opening and closing all the time. if the water doesnt stay in the radiator long enough it wont cool down but if it stays in the engine to long the water gets too hot. there is always a ratio your trying to find. try a hotter thermostat and then try to speed the flow of water up if that doesnt work try to slow it down

[cjmccall]

Tirod,
Thanks for your input and information. Last night I turned on the A/C just before I got home and the temperature went up to 221 degrees (air temp 85+)just as I got to my house. This is real close to boiling over.
To elaborate a little further I have the shroud from Mike Iverson. I just closed off the areas along side the radiator, top and bottom to force all the air over the core and not bypass or get sucked around the top and bottom. This did not seem to help at all. I too have thought about too fast of flow not having a chance to cool off before re-entering the engine. Which brings to mind the different theories of running without a thermostat or not. One says take out the thermostat, the next says don't because the water flows too fast to cool. The thermostat I have in there is a 160 degree, high flow model. The fact that this engine has always run what I consider too hot and nothing I have tried seems to have improved it, maybe there is something wrong with the way the engine was built ( brand new GM crate engine) or some restriction in the heads or block.
I have talked to Afco that makes the radiator for the hot rod and they insure me it should handle 500 plus HP engines. FF said they know of no one have overheating problems. There are cars running way bigger, supercharged engines than my 290 HP SBC.
What has got me completely baffled is how all these other builds don't seem to have any running hot problems using the same components.
I think I will try going back to my stock water pump and see what this does.
Has anyone ever bought a GM crate engine that was put together wrong ??? I just feel like a fisherman and can't catch the right fish.

[450dude]

616 510 3411 give me a call i can give you a couple things to try
my 33 is 1266 hp i have no problems

[Richard Oben]

Have you verified this with anything but the gauge. I have seen many gauges not read correct. I have seen them be 15 degrees off. So you may be at 195 not 210. Just throwing stuff out there. If it has never overheated I would think it is not going to at 3800 miles. HTH, Richard.

[ehansen007]

Originally Posted by 450dude

my 33 is 1266 hp i have no problems

Wait........WHAT???? God I hope that's a typo. Or maybe not!

[britpit]

Gotta jump in here and ask - does the fan turn in the correct direction so that it is pulling air through the radiator and not pushing it forward toward the grill?

Another thing to try - while the engine is running, take a water hose and spray the radiator from the engine side. It should cool the engine off to where it is running at the opening temperature of the thermostat. Then check the gauge - should be 160 or so degrees. If the gauge reads high, perhaps the sending unit does not ground itself in the intake manifold well enough and the gauge thinks the engine temp is higher than what it really is. Or maybe the thermostat is bad.

A high-flow water pump should not cause a high temp reading at idle and low speeds due to laminar flow so I don't think that's it.

Wayne P.

[450dude]

no typo

[Tom Veale]

I'm with Richard O on this one. If you know a friend with an optical temp gauge, have him/her shoot the top and bottom tank of the radiator to make sure there's temp differential. You'll also find out if the gauge is near accurate or not.

If you start with a cold engine, such a gauge can be used to tell at what temp the thermostat is opening.

I don't own one, but a guy I know who has an auto "fixit" shop does and he's helped me in the past. Usually I've had problems with "stuck open" thermostats heading into winter in the past.

[cjmccall]

I have an infrared temp reader and have measured the top and bottom tanks and they run 50 t0 60 degrees different. Which makes me think the water is circulating OK. I don't know what the differencial should be between top and bottom tanks. Has anyone looked in their radiator to see if the coolant is flowing into the top of the radiator? Any input? I have a radiator pressure cap with built in temp. gauge, the gauge that came in kit, and another sending unit that is in the intake manifold on the opposite side as the FF sending unit (each side of thermostat housing) that is for the EZ-EFI system I installed resently. The radiator cap reads the highest by 5 to 10 degrees, then the new EFI sending unit which has a digital readout on the hand held computor reads close to the radiator temp. but about 5 degrees hotter than the FF gauge.
The higher CFM fan I installed is pulling the air thru the radiator (not pushing). I have Mike Everson's fan shroud and sealed around radiator and grill to force all air thru radiator and not by-pass around it.
I have the MSD distributor set at 34 degrees total advance ( no vacuum advance). No spark knock or hard starting.
I appreciate everyone's input and will try some of these sugesstions to solve my problem.

[nsxpert]

Can the overflow tank have any effect on the overheating? I feel it is to small and needs more capacity when the engine gets to hot and recirculates it has gone dry on me and then overheat

[cjmccall]

I have a quart and 1/2 overflow tank.

[FFR5452]

Unless the water pump has a broken finger, you've just about covered everything external that could be causing your overheating.

The next thing I would do would be to replace the thermostat with a 180 degree unit in order to rule out a malfunctioning (partially opening) unit. Did you drill any holes in it before installing it? If so, it could be staying closed and only the holes are letting water pass. Thus cutting the flow down and causing the overheating.

If that doesn't solve it, I would then suspect a head or intake gasket failure. hopefully it's the thermostat.

[Arrowhead]

Cooling problems can be tough to diagnose. First off when do the temps climb the most? On the highway or stopped in traffic? (oops read that it's stop and go where your having the problem) Have tried water wetter? (may or may not help) Is the coolant reservoir being drained when the engine cools off overnight? If it is, it's introducing air into the system that can be trapped again.

If you start the engine cold and leave the radiator cap off and run it till it warms up, you will be able to see the water start to circulate. You can use a meat type thermometer to see if it's starts circulating at the right temperature.

You could try taking the side panels off completely and see if that helps. Unless your openings are huge, it may still be starving for air. Our cars are pretty low to the ground and the hot air gets trapped in there.

Also, a 15 pound cap is good to around 265 degrees with a 50/50 mixture, less with more water. So I think your a ways away from boiling over, but it is unnerving when it starts to climb.

As long as it's not boiling over, I don't get too excited about the actual temperatures anymore. Ironically, the higher the temperature of the coolant compared to the temperature of the air coming in, the higher the capacity it has. The increase of the coolant temperature is just the system trying to find it's equilibrium. There are other factors like timing and fuel that will make and engine run hot and no amount of modifications will keep it cool either. I’d check into that too.

[tirod]

To answer the one poster, a thermostat simply cannot force an engine to run at it's temperature. This is exactly an example why. The OP has one installed, but the system's natural equilibrium at this point is to run at 200+. Obviously, if the stat is full open, it can't get the temp down any further because the system isn't doing it.

Stats can't force a system to run cooler if it doesn't have the capacity. All they do is close off flow and force it to run hotter than normal.

This system isn't running at 160, or even close, which means the radiator isn't cooling the outflow enough regardless of what it's "supposed" to do. There's not enough heat transfer. Using a temp gun will show exactly what is happening in the core and is a good suggestion.

Custom cars don't get the extensive track testing in extreme climates factory cars do. We drive them out of the garage onto the street in beta mode, and find out what does and doesn't work.

[mctavish]

If your distributor has a vacuum advance pot, try using it. +10 degree vacuum advance (full manifold vacuum) at idle will help to cool it off. I have the same crate motor in my 31 Ford pickup, no cooling problems with vacuum advance, stock flow WP and stock thermostat. Stays at 180 all the time, even at 90+F air temp using belt driven 17" fan.

[nsxpert]

Fixed my overheating issue. Replaced thermostat with OEM brand none of these advance auto parts or pep boys off brands. And sure enough problem solved

[ehansen007]

Well this sure helps me. I was on my way out to the race track yesterday and heading down a hill it was running at 150 or so. Then when I hit traffic, it shot up to 230! It was scary! Luckily I was able to keep it moving after that by spacing out but it would just go up and down. I did use one of those Pep boys thermos and this may also be the reason. I certainly can't have it running like that anymore. I really hate this thermostat thing. It's been a pain in the butt from leaking constantly to now where it's not working. I tried running without a thermostat but then it wouldn't warm up properly in the mornings.