68 overheating
 

Hi need help to determine cause of overheating.
396 4 spd 373 rear

The car came to me this way a sepentine set up, the drive pulley is 5 1/2 inches and the water pump pulley is 6 inches diameter. I am in central florida and its in the mid 90s already
I took out the 180 new thermostat that i put in a few weeks ago because i overheated in stopped traffic. But today with the theromsat removed and not moving it was running hot again between 190 and 205 .
I have a newer be cool 4 pass aluminum radiator with an electric 16 inch fan and it comes on around 190 and goes off around 170 deg.

any suggestions on where to start to determine my problem would be appreciated.
Thanks
Ted

ps i would like to know if i need to change the water pump for a serpentine type one. and is there any difference between a stock one and this??
:icon_shrug:

Was the thermostat bad?
The thermostat functions two ways. First is to keep water in the engine to assist in warming the engine up.

The second thing a thermostat does is it restricts flow into the engine, thus causing the antifreeze to remain in the radiator a bit longer, which allows the antifreeze to cool down a bit before going back into the engine to cool it. If the antifreeze doesn't spend enough time in the radiator, it isn't cooled properly which means it's not going to cool your engine properly.

In short, not having the proper thermostat installed, or no thermostat installed can cause an engine to overheat.

I'm assuming that air flow through the radiator is unrestricted and your getting good flow through the radiator? You said the radiator was "Newer", but it doesn't take long for them to become clogged especially if somebody used tap water.. I'm also assuming that your running 50/50 mix antifreeze?

Good luck and keep us posted.

Check to see how the serpentine is driving the pump. Most serpetines use the back of the belt to drive the water pump pulley. If that is what you have, then you need a water pump designed for reverse rotation.

I have plenty of flow in the radiator and it is a 50/50 mix in there but i have to check the rotation of the pump. Which way is the normal rotation of the pump clockwize or counter clock wize ? also the radiator is free of any debri in the finns.My problem is that this is the way i got the car and i am not sure if the water pump is correct. the flow however is going in the right direction in the top and out the bottom. Should the pump be turning clockwize or counter clock?

As I explained before, check which side of the belt is driving the pump. If the smooth side of the serpentine is driving the belt you need a reverse rotation pump (counterclockwise). If the ribbed side of the belt is driving the pump, you need a standard rotation pump (clockwise). What determines which way the water flows is the angle of the fins on impeller inside the pump. On SBC the flow is from the heads to the top of the radiator, and from the bottom of the radiator to the block.
Being that the engine overheats in traffic and is OK at highway speed, there is a possibility that the fan is not pulling enough air, or that the pump is turning too slow, or both.

Thanks pete for the info, the pump is being turned by the ribbed side of the belt.

Not sure if you ever put your thermostat back in or not... but is is possible that your running too much ignition advance at idle?

Another thought, cann you verify air flow from your fan? Is it possible they were wired backward and running in reverse so instead of pulling fresh air from outside, they pushing hot air from inside the engine bay?

That's about all I can think of for now.

I put a 160 thermostat in and the fan is blowing in the right direction towards the motor will try it again in a few days.

also to make sure i did order new pulleys a 7" crank and a 5 1/4 " water pump pulley which will turn the water pump faster at idle and bumper to bumper speeds. hope this helps!!!!!!!!!!