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Discussion Starter #1
I'll be honest, this is my first big block. I have a 71 nova with a 454. it starts right up and drives great, for about 10 minutes. The water temp jumps up past 250 in about 10 minutes, then it begins to lose oil pressure, i assume because the oil gets hot and thins out. I replaced the thermostat yesterday, changed to a thicker oil (30weight), flushed the coolant. then this morning i started it, it idled for a while with the temp staying around 150, then i take it down the road and within minutes again the needle is pegged to 300 and the oil pressure went from 60 down to about 5 before i shut it off. it wasn't spitting coolant, the radiator was still topped off. oil was misting out of the breather. what is the next step i should take? should i use an aftermarket electric fan? could it be the oil pump? thicker oil?

there are no leaks under the car, it's just getting too hot way too fast.

please help.
 

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Ten Commandments For Maximum Cooling

1. Thou shall make room for an adequate cooling system in the design of your engine compartment.
First things first. When planning your performance vehicle, remember that you’re building it to drive, not to sit and steam. Plan adequate space for the cooling system including the radiator, fan, shroud, over flow tank and mounting brackets. Talk with a cooling specialist to help you size the system for your vehicle, engine and driving habits. Consider the investment compared to the total cost of the car.

2. Thou shall shroud thy radiator when using a fan.
Fans move air through the radiator assisting in cooling the engine. A fan without a shroud is better than no fan. But, consider this. At idle or cruising speeds, you need the entire cooling system working at its optimum. An unshrouded fan is moving air through only the portion of the radiator equal to the surface area of the fan. For example, on a ’32 Ford, the area of a 15.50” fan is about 189 sq. in.; the core of the radiator is approximately 371 sq. in. This means that almost 49% of the unshrouded radiator is not receiving any benefits of the fan. Shrouding your radiator lets the fan pull air through the entire core.

3. Thou shall use an electric fan.
Rule of thumb. Only choose a mechanical fan over an electric fan if it’s your farm tractor. An electric fan is preferred because when you need a fan the most (at idle or cruising speeds) an electric fan is delivering maximum air independent of engine RPM’s. Fans that move 2000-2300 CFM’s are worth the investment. Preference should be given to a “pull” vs. a “push” fan. Mounted on the engine side of the radiator, a pull fan does not interfere with air flow at highway speeds. All shrouded fans should be on the engine side of the radiator.

4. Thou shall consider airflow or how a radiator cools.
Without adequate air flow, a radiator is just a reservoir for hot water. Coolant transfers heat to the tubes; the tubes transfer heat to the fins; air moving through the fins dissipates the heat from the radiator. You need sufficient openings to the radiator that channel adequate air to the entire surface of the radiator. You must have a radiator design that allows the air to pass effectively through the radiator (wider and taller is better than thicker). You must consider how the heat will be evacuated from the engine compartment.

5. Thou shall use the proper water pump pulley ratio.
To obtain the maximum operating efficiency rate for your water pump at highway speeds, you should overdrive the pump by 30-35%. Check your pulley selection. Most after market pulleys are a 1:1 ratio. For a 30-35% overdrive, the crank pulley should be approximately 7 7/8” and the water pump pulley approximately 5 3/4”. This overdrive provides proper coolant flow from the engine and through the radiator.
 

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6. Thou shall consider the effects of the pressure cap
The higher rated the pressure cap, the hotter the water has to get to boil. One pound of pressure raises the boiling temperature 3°F. A 16-pound cap raises the boiling point to 268°F. If your engine is designed to run at 200°F, a 14-16-pound cap should be sufficient. Running a higher pressure cap to prevent boil over is putting a band aid on another problem that needs to be fixed. Higher operating pressure places additional stress on the entire engine system and increases the potential of hoses bursting and possible injury.

7. Thou shall understand the operating temperatures of today’s modern engines.
All engines have “normal” operating temperatures. Running engine temperatures well above or below recommended temperatures could cause damage. Most of today’s engines operate in the 180°-210°F range. Pollution laws, new oil blends and higher combustion gasoline have forced engine design changes that have increased operating temperatures over the past decade. Consider your engine’s normal operating temperatures when selecting your radiator’s cooling capacity.

8. Thou shall always use a thermostat.
The thermostat controls engine coolant temperature. It stops the flow of coolant through the radiator until the coolant reaches the thermostat’s preset temperature. Operating your engine within its temperature parameters reduces wear, helps control emissions and turns any moisture in the crankcase to steam where it is removed by the PCV system. Select the right thermostat for your engine’s operating temperature range.

9. Thou shall protect thy cooling system with recommended coolant.
It is essential to use a premium coolant that protects the radiator, other metal parts and seals. Today’s coolants are a scientific blend that normally includes water wetter and corrosion inhibitors. Use of a coolant that contains no silicate is recommended. Silicate is an abrasive and can cause gel formation and water pump failure. A 50/50 mix of coolant and water provides the best overall cooling efficiency. Proper maintenance (regular flushing and changing of coolant) will extend the life of your system.

10. Thou shall spend thy money wisely
If you are having cooling problems, begin by looking at the least expensive fixes first. 1) Add an electric fan. 2) Shroud your fan. 3) Check your belts and hoses. Slipping belts or collapsed hoses mean trouble. 4) Check your radiator cap. 5) Flush and refill with premium coolant. 6) Use the proper thermostat. 7) Clean the radiator of foreign materials. 8) Overdrive the water pump 20-30%. 9) Check your water pump. Should cooling problems persist, it may be time for a new performance radiator from Griffin. Call the Griffin Customer Service Department at 1-800-722-3723 for assistance in selecting the correct radiator for your requirements.

http://www.griffinrad.com/tips.php

Engine timing, running lean and other stuff can make a big difference also. I would make sure your distributor advance is working; if it isn't moving runing really slow timing at speed can really heat up the engine.
 

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Good information. Not to flame or anythting, but I love how it says do the cheap stuff first, but if you're having overheating problems, the first thing it says to do is buy an electric fan. :p

Matt
 

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Discussion Starter #5
supernova, i was thinking the same thing, lol. i found a few taurus fans on ebay last night all averaging about $40.

nova guy, thanks, very helpful. i currently have a shroud on the car. i am flushing it today. i already installed a new thermostat, i am going to try a different cap too. i am going to order a taurus fan (i assume they set up pretty easily). i hope this stuff helps because i cant afford a whole lot more, we've got 5 kids. the car will probably go up for sale soon anyway, i just want it running perfectly for any future owner. THANKS
 

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Good information. Not to flame or anythting, but I love how it says do the cheap stuff first, but if you're having overheating problems, the first thing it says to do is buy an electric fan. :p

Matt
Not to be too argumentative :p , but I think that throwing on an electric fan might be a bandaid that would be masking other efficiency problems in the cooling system that are contributing to the overheating. Don't get me wrong, electric fans are great, but guys and auto manufacturers had been building these things for years with mechanical fans without issues.

Throwing more air over an inefficiently cooling radiator is just going to mask the problem for a little while until the system becomes even less efficient.

I'd start looking into seeing how badly the radiator might be gummed up (from years or use or storage) to see if that could be affecting the rad's cooling efficiency. It might need to be boiled out at a local rad shop. It's also possible that your rad isn't rated for the BTU output of the big block. Were the factory rads different in the BB vs. SB in the 71. Was it a stock BB?

As stated, the proper cap (16lbs?) may be needed, if not already there.

Best of luck.
 

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A cap wont change how the engine cools, it just keeps the coolant in until catastrophic overheat.

Some things to check, some common, some not so common. (300 degrees is scary)

If you have a clutch fan, check the drag on the fan when the radiator is hot. (Engine off). If it turns easily, clutch fan is shot. Usually overheats at extended warm idle and under 40 mph.

Make sure the fan is a puller, not a pusher. When running does it pull air through the radiator and push it back on the engine?

Make sure you don't have an air bubble in the block. Did you measure the amount of coolant it took originally?

Run a compression check. All plugs out, throttle open, check all 8 cylinders. Make sure you don't have a bad head gasket.

Check for a VACUMM leak this can make the engine lean an d hot in a hurry. Does it have good power like it should, no pinging etc before it gets hot? If not, could be a vacumm leak. Sometimes the vacumm leak can be with the intake gaskets, instide the engine. Some extreme cases carb is set too lean.

Look for kinked/pinched radiator hoses that block the coolant flow.

What year/direction water pump. Since serpentine belts came out some water pumps go the other direction. I don't know if this is a problem with big block pumps.

Is the water pump any good? Start cold with the cap off and watch as the thermostat opens. Is the water pumping through the radiator well?

What pulley ratio. If a drag setup, a small crank pulley for drags, that may not be good at all on the street.

What radiator are you using? How many cores/rows deep is it?
 
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