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Old 10-17-2011, 07:03 AM
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radiator pressure to correct radiator cap lb pressure

I am trying to obtain the formula for having the correct water cap lb for a 4 row radiator for a high performance 1966 327/350 hp
engine...I current have a 16lb cap on a 4 row radiator and I am trying to determine if the cap is the correct cap---experiencing an engine heat problem and want to cover all basis

Thx,
Russ

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Old 10-17-2011, 08:19 AM
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Going to a higher capacity pressure cap does not change the overall operating temps. What the pressurized cap does is enable the coolant to reach a higher temp before boiling.

If the radiator is built correctly it should be able to use a 16 lb. pressure cap and that size cap is more than likely the suggested cap.

Using the correct thermostat will also effect the coolant temps. I suggest you use a 180 degree thermostat for your application.

What do you consider to be a "heat problem"? Running around 195-210 at operating temps is normal for your small block Chevy engine.

There are several areas to consider when you are having a "heat problem".

First is the ignition timing. If it is even slightly retarded the engine temps will cause the coolant temps to be higher.

Second would be an excessive air leak causing the engine to run very lean. Check that all sources for vacuum leaks (primarily on the intake manifold or carb base) are either blocked off or have the hoses connected.

Next would be a good air flow thru the radiator core.

Included in this is having a good shroud to help direct the air flow and a sufficient fan.

The stock non-clutch style mechanical fan will work best. Clutch style fans often do not pull enough air at lower RPM's and I do not recommend them. Puller electric fans can be used. A shroud is highly suggested with any electric fan. I don't recommend using a thermostatically controlled electric fan because of potential failure of the thermostat. Wire the electric fan so that it is on whenever the ignition switch is in the ON position. A toggle switch would work IF you remember to turn it on. Pusher style fans are the least efficient and can actually block the airflow. I do not recommend this style electric fan.

Another item to consider is the coolant. Water works best with no additives. Up to a 50/50 mix with the green anti-freeze works well. The beige (tan) environmentally safe anti-freeze has a tendency to gel over time and can plug up the cooling system. Aftermarket additives such as 'Water Wetter' should not be needed if your cooling system is installed correctly and sized for your needs.

An additional area to consider is where the temp sending unit is located. For example: on your small block Chevy engine the best location for the sending unit is in the intake manifold near the thermostat housing. This will give a more accurate figure for the coolant temps. Depending on the year, GM installed the temp sending unit in the side of the cylinder head. This will yield a higher temp because of the close proximity to the exhaust valve near the temp sending unit installation point. The temp reading from this area can be as much as 20 degrees higher than the actual coolant temp.
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Old 10-17-2011, 08:43 AM
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Thx for your insight--it is very muck appreciated,
russ
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Old 10-17-2011, 08:50 AM
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I read on some Pontiac forum that some guy was having a over heating problem well it turned out that the upper radiator hose was above the height of radiator and once he lowed it the car ran fine. Make sure your fan shroud is on the car if not it will over heat for sure.
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Old 10-17-2011, 09:19 AM
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Thx for your insight---appreciate your thoughts--the shroud is on the car with the fan in the correct position and the upper hose is below the radiator into the mainifold--a very confusing problem that i am experiencing
thx again,
Russ
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Old 10-17-2011, 11:59 AM
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wow Frisco nice post
I learned something too.
maybe I'll exchange my pusher fan for a puller.
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Old 10-17-2011, 12:31 PM
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Glad to hear that someone else learned something
Russ
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