Cooling problem

I have had good luck bleeding air out of the cooling system by pulling the heater hose off the upper heater core port, with the engine off, and then filling the radiator. When the coolant is one inch from the top of the radiator, or when coolant runs out of the open port, replace the hose and then start the engine. You may need to add a little more coolant.

 

It's TWO 1/16ths." holes NOT 2 & 1/16ths.

 

A single 1/16 hole has a diameter of 0.0625. You want two of 'em.

The pin drill in my (previous) photo is a #76, I think. It's what fits into the triangular opening created by the stamping process. The passageway created is a bit larger than the 0.020 of a 76 bit, but wouldn't flow well due to the narrowness of the corners. Air flows easily, more-viscous liquid coolant, wouldn't.



Rounding UP to a fractional size drill bit, a SINGLE 1/32 hole (0.03125) would be generously oversize compared to the vent stamped into the Robertshaw 'stats, and wouldn't have the flow-restricting narrow corners.

If bigass holes were so beneficial, why aren't thermostats engineered with them from the factory? The thermostats that do have larger vents, have jiggle-valves intended to close when the engine runs. The holes are only open when the water pump isn't moving coolant.

 

Ok guys I took some of all the advice and this is what I did. I removed the thermostat completely to eliminate the possibility of air, filled the radiator to about 1” from the top and started it up with the cap off water immediately started circulating and went down in the radiator, I filled the radiator to the top after increasing the rpm to 1500 then capped the radiator and filled the overflow tank to its proper level. I ran it at idle for 15 min. no leaks anywhere and the water temp never went over 170 and this was with the cowl off. I plan on putting the thermostat in tomorrow and replacing the bypass hose it’s pretty worn out. I’ll install the cowl and that should button it up. The 470 is running good and sounds as awesome as ever. I got lots of good information thanks to you all who responded.

On The Eighth Day God Created Buick