Radiator Fan

[Don5]

BTW- my 79 came with a fixed blade fan and I replaced it with a clutch fan. I have never had the issue that you are having. I also did have a brand new thermostat stick shut on me the very first time I fired a new engine up. You might have to get another thermostat. Yours might be defective.

My shroud dimensions are: 7 blade fan, shroud is 7 inches deep, the fan blades are inside the shroud 1/2 inch and the inside diameter is 22 inches + or - a little bit.

[enaberif]

I put a 190 into it. But using a infrared gun the water neck never gets over 170-175* F

I am going to put a block off plate so less air gets to the water neck to see if it helps.

[LTZ C20]

195 is stock temp. Maybe a 200 or 210, I know it's higher but maybe it will compensate and get you up too the proper temp. Besides, a 350 will run 210 no problem.

[enaberif]

Sorry yah its a 195 lol.

[timthescarrd]

If the thermostat isn't opening, then coolant is never exchanging between the block and the radiator, so your water neck will always be the temp of the coolant in the radiator.  I would use your thermometer to check the temp of your intake and heads.

The only way the fan can be over-cooling if the thermostat is not opening, is if it is pushing enough air over the block to air-cool it (like a motorcycle or old VW engine).  If that's the case, I would begin to suspect how well the engine is running

[bd]

These may sound ludicrous, but (1) how are the heater hoses plumbed, and (2) what happens if you pinch off the heater hoses?

[enaberif]

If the thermostat isn't opening, then coolant is never exchanging between the block and the radiator, so your water neck will always be the temp of the coolant in the radiator.  I would use your thermometer to check the temp of your intake and heads.

The only way the fan can be over-cooling if the thermostat is not opening, is if it is pushing enough air over the block to air-cool it (like a motorcycle or old VW engine).  If that's the case, I would begin to suspect how well the engine is running

Well ironically when I pull the fan off the thermostat will open just fine and work as normal. What would cause a vehicle to not run right to cause this though? You are basically saying the engine itself is running cool.

These may sound ludicrous, but (1) how are the heater hoses plumbed, and (2) what happens if you pinch off the heater hoses?

The proper way... 3/4 to pump

I will check the temps of the heads on the next test.

[Don5]

Top hose goes to the water pump and the bottom hose goes to the intake. I know you know but just so you don't get confused. Just tryin to help.

[bd]

These may sound ludicrous, but (1) how are the heater hoses plumbed, and (2) what happens if you pinch off the heater hoses?

The proper way... 3/4 to pump

So does clamping off coolant flow through the heater have any effect whatsoever?

[enaberif]

These may sound ludicrous, but (1) how are the heater hoses plumbed, and (2) what happens if you pinch off the heater hoses?

The proper way... 3/4 to pump

So does clamping off coolant flow through the heater have any effect whatsoever?

Haven't tried yet. Curious what this will accomplish?

[timthescarrd]

Well ironically when I pull the fan off the thermostat will open just fine and work as normal. What would cause a vehicle to not run right to cause this though? You are basically saying the engine itself is running cool.

Usually an engine will run cooler than normal if it's running rich, it's not firing all cylinders, or the outside ambient temp is very low.

Being June, we'll assume it's not below freezing outside. Running that rich I would expect you'd notice black smoke from the tailpipe.  I've seen engine run on only one bank and still feel fairly smooth, so you might check the temp of the exhaust manifold near each valve, those should be decently consistent.

[Irish_Alley]

kind of going of what tim said but just curious whats your timing set at?

[enaberif]

Well ironically when I pull the fan off the thermostat will open just fine and work as normal. What would cause a vehicle to not run right to cause this though? You are basically saying the engine itself is running cool.

Usually an engine will run cooler than normal if it's running rich, it's not firing all cylinders, or the outside ambient temp is very low.

Being June, we'll assume it's not below freezing outside. Running that rich I would expect you'd notice black smoke from the tailpipe.  I've seen engine run on only one bank and still feel fairly smooth, so you might check the temp of the exhaust manifold near each valve, those should be decently consistent.

You would be correct and on most days lately its been well above 15 degrees celsius. No black smoke to be seen at all and I will definitely check the exhaust manifolds to see what they say.

kind of going of what tim said but just curious whats your timing set at?

Right now its running at 16* BTDC.

[enaberif]

Ok so I did some testing.

Truck warmed up and running for 30 minutes.

Cylinder temps on the head just above the ports is betweem 280-380 with 7 and 8 running cooler.

Water neck gets up to 182-185. If I wrap the water neck with insulated bubble wrap I will seen a immediate increase in temps of 193-195

Also water pump pulley is smaller than the crank pulley. Water pump pulley is 6.25" and the crank pulley is 6.75-7"

So by wrapping the water neck I am seeing a 10 degree increase of temps which leads me to believe my fan is blowing too much cold air.

[LTZ C20]

Water pump pulley being smaller than crank pulley is normal.