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Old 03-28-2014, 06:35 PM
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Chevy Small block 400 cooling system issues

ok so I am getting ready to get my street rod out for the spring and get some thing I want done before the first show of the season here in may. but, last year at the last show of the season we were staging to park and my car started to run a little warm up around 220. it was definitely up in the high 80s that day, but I want to get my cooling system lined out to where my car can stay cool in traffic. so I would like to have some of you look at my set up and see if you have any suggestions.

I have a 38 dodge sedan with a 400 chevy small block. the 400 is stock bore and runs edelbrock aluminum complete heads and aluminum rpm air gap intake. the water pump is an aluminum one that was listed as high flow from skip white performance. I have a 195 thermostat in it and cooling is provided by an aluminum downflow radiator and a 16" puller aftermarket electric fan with out a shroud right on the radiator.

ignition is in a HEI, and fuel is a 650 holley DP. I do run a crane mutha thumper cam that is pretty aggressive and lopey. I am also getting my temp reading from the bung in the side of the head. steam holes were drilled as directed in the aluminum heads.

I just feel that I have all good components and that I should be able to get her to run cool.

I appreciate any opinions. and I can provide specific part numbers if needed.

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Old 03-28-2014, 07:00 PM
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Put a shroud on the radiator, makes a huge difference. My "T" bucket has a radiator like a large postage stamp. But with an electric fan and a shroud it seldom sees 195 degrees.. Blower on a 383 and sometines a 406 when I'm tinkering..
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Old 03-28-2014, 07:10 PM
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consider this....

What is you timing at idle?

Are you running under drive pulley? I ran under drive pulley on my 400 for about 2 weeks, It over heated. I put the stock ratio pulleys back and no more over heating at idle.

Some hot rods have a cooling system hose configuration that traps air. You may need to add a bleeder at the thermostat housing to purge trapped air.

The 16" fan with no shrowd seems suspect to me. You may want to add some additional shrouding, an under tray or something else to ensure hot air from the back of the rad doesnt migrate to the front. A picture of the rad and fan setup would be a great help.
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Old 03-28-2014, 07:16 PM
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Get the electric fan off the radiator and fab up a shroud that forces the fan to pull from the whole core and mount the fan to the back end of it...., right now you are only using a 16" diameter section of the radiator for cooling, the rest you are wasting.
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Old 03-29-2014, 08:16 PM
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well I can try a shroud easy enough. does any one have any opinions about the curved blade fans vs the straight?
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Old 03-29-2014, 11:47 PM
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Do you have an overflow tank and what pressure cap do you have?
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Old 03-30-2014, 04:11 PM
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Most aftermarket electric fans flow way less than stated. Without a shroud they do very little in the way of cooling.

Personally I would go with a OEM Ford fan from the mid 90's
18" Lincoln / T-bird electric fan will cool just about anything
17" supercharged T-brid fan works very well also
16" Taurus fan works good if space is tight.

If you get one from a junk yard bring a 12-18v drill battery pack so you can test both speeds in the yard before you bring it home.
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Old 03-30-2014, 06:03 PM
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Just a thought, I know if your idle mixture is to lean it will make an engine over heat.
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Old 03-30-2014, 06:09 PM
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Quote:
Originally Posted by BOBCRMAN@aol.com View Post
Put a shroud on the radiator, makes a huge difference. My "T" bucket has a radiator like a large postage stamp. But with an electric fan and a shroud it seldom sees 195 degrees.. Blower on a 383 and sometines a 406 when I'm tinkering..
What he said, I have a 406 in my car and until I put my electric fans with a shroud on, it would eventually start getting hot, now, no problems with heat even on 90+ hat days going to a cruise or show.
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Old 04-04-2014, 12:38 PM
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I am not running a overflow currently. Space is pretty limited in my engine compartment. It doesn't seem to throw out that much water.
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Old 04-04-2014, 09:18 PM
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You DID drill steam holes in the heads and the head gasket RIGHT???

I have a bored and stroked 400, now 434 puts down 500 ftlbs.
That engine will run all day and not get hot, I idle around the car craft summer nats in the 95 degree heat with no worries
It does have a flexilite dual electric fan, but it pulls it right down
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Old 04-04-2014, 10:05 PM
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400 Chevies have siamesed cylinders ... never was a fan of that.

Temp sender in the cyl head usually results in a higher reading on the guage due to exhaust heat. I would try moving that sender to the intake. Factory gauges were calibrated to "expect" this higher temperature, but aftermarket sender/guage combos are not.

Are you running a 50/50 mix of glycol & water?
What are you running for a rad cap (PSI)?
Is it boiling over?

How Stuff Works article

Quote:
Fluid - Freezing Point - Boiling Point
•Pure Water: 0 C / 32 F - 100 C / 212 F
•50/50 mix of C2H6O2/Water: -37 C / -35 F - 106 C / 223 F
•70/30 mix of C2H6O2/Water: -55 C / -67 F - 113 C / 235 F

The temperature of the coolant can sometimes reach 250 to 275 F (121 to 135 C). Even with ethylene glycol added, these temperatures would boil the coolant, so something additional must be done to raise its boiling point.

The cooling system uses pressure to further raise the boiling point of the coolant. Just as the boiling temperature of water is higher in a pressure cooker, the boiling temperature of coolant is higher if you pressurize the system. Most cars have a pressure limit of 14 to 15 pounds per square inch (psi), which raises the boiling point another 45 F (25 C) so the coolant can withstand the high temperatures.

Antifreeze also contains additives to resist corrosion.


Classic Instruments
Quote:
#5 Temperature / Oil Pressure Reading Too High


Where is the sending unit mounted?

Are you using our sending unit?

Is there Teflon or some other sealant on the sending unit threads?

Is the gauge grounded well?


If sender is mounted in the engine head, it will read 15 – 20 degrees higher than actual because of heat from the exhaust. Relocate the sender to the intake manifold if possible. (LS1 engines should have temp sender installed in the head and are not affected by exhaust heat.)

If the gauge has a bad ground, it will make the oil pressure or temperature gauge read high or even peg (if there is no ground).

If the sender has a bad ground (caused by Teflon tape or other sealant), it usually causes a cold reading but in some cases will cause the gauge to read high.

Make sure customer is using one of our senders. It should not be in any bushing (size adapter), which will cause bad readings. Our sender can be identified by the numbers stamped into it near where you would put a wrench to it. The number should be 02025, 02024, 02023 or 02022.

Hot readings can be caused by air pockets in the system. When the vapor in the air pocket passes the sending unit, the temperature will increase higher than the actual coolant temperature. It may be necessary to “burp” the coolant system to remove any air pockets.

Make sure you have the proper coolant level for the cooling system
.

Last edited by 66GMC; 04-04-2014 at 10:24 PM.
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Old 04-05-2014, 06:52 PM
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I think my cap is 12 psi. I had wondered about the sender in the head, seems like it has the probability to read high. I have shorty tight tuck headers so it runs close to the head.
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Old 04-06-2014, 11:17 AM
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If it was mine, i'd 1st. drop in a 180* stat, try & install a shroud, even if its a 1/2 shroud, then if at all possible, run twin fans, or install a flex fan or clutch style, i'm sure you can squeeze a narrow flex fan it in, I ran a 406 with 10.4 compression in my G Body, 180* stat, shroud & clutch fan, It NEVER got over 185*, that was in traffic & 90+*.
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Old 04-07-2014, 06:57 PM
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I'm going to try the shroud first. Finally found one that fits, also found a place for custom sized ones reasonable too. First order of business. I have to move the radiator forward a few inches. So i will make the change and let everybody know what the change is. Then I will make other changes, I only like to change on thing at a time so I know exactly what the results are.
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