I have a 396 with a 180 thermostat. The car wants to run 197, when I put a line clamp on the bypass line the car runs at 187. I take the clam off it hose back to 197. Just sitting idling it runs 187 clamped or in clamped. Is this bypass line needed or can I just plug it?
You didn't fill in your location so I can not answer your question. The by-pass hose is necessary if you live in a cold climate. In Central Florida it is not needed, and most around here block the ports with pipe plugs. In Nome Alaska, that is a different proposition.
I live in Tampa fla. when I plug the intake an the water pump do I need to drill 2 holes in the thermostat or get one with the holes in it. In the past I tried a 160 thermostat it also ran 197-200
I think the issue is in your water pump. If you close the by pass hose and it has has any affect at all on cooling then water flow is an issue.
The factory water pump uses an open paddle wheel that attempts to beat the water into submission. An enclosed water pump wheel such as used with an Edelbrock aluminum housing water pump will assure you that the the blades are uniform in length and the water is being forced from the inside pick up point to the inside of the casting. Better yet you can move twice the volume of water with half of the horsepower to drive the pump by buying a Stewart water pump that has a scroll impeller instead of a paddle wheel and a casting with a positive displacement that controls the water path.
Usually if your car over heats at idle but not at cruising speed then the issue is with your fan and shroud. If it over heats at cruising speed the radiator is the problem (assumes you have good hoses).
I have an Edelbrock water pump. The engine has never gotten over 209 during the hotter months of the summer. i just noticed it ran 10 degrees cooler with the bypass line clamped. So that is why am considering plugging the intake in the top of the water pump.
If you have a candy thermometer (accurate to a tenth of a degree F) you can pop the radiator cap (when it is cold) to see what your actual temp is quite easily.
The bypass hose takes hot water back into the pump & mixes it with the cooled water from the radiator which is used to cool the engine. This will cause the car to run hotter, when you are at the limits of the radiator capacity, as you have proven.
If you had sufficient cooling capacity it would not make a difference as the stat would be trying to raise the temp, whereas your car needs all the cooling it can get & is already running above the stat setting.
The reason for the bypass is to allow circulation in the engine when the stat is closed.
You can always block the bypass & run the stat with two or more 1/4" drilled holes in it. The car will take slightly longer to warm up & may run slightly below the stat setting in very cold weather but at least all the water is now flowing through the radiator. Also allow the car to warm up slightly before exposing it to high RPM as you are essentially nearly blocking all of the water pumps flow.
You can also get a small freeze plug, drill a hole in it & place it in the bypass line instead.
I’ve questioned the radiator before, griffin swears it will cool up to 700 hp. I’m running 380 at the wheels. I do like drilling a small freeze plug idea
Get a freeze plug & drill a 5/16" hole & see how it works.
Freeze plugs are cheap & easy to try, but keep in mind, the best cooling will still be from blocking the bypass entirely & running a drilled stat.
Also if you have a heater in the car & there is no isolation valve on it, you are also continuously recirculating water through it & can safely eliminate the bypass completely. In this case, you can just stick an undrilled freeze plug in the bypass & leave it connected for a proper look.
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