I asked this question on my "160 versus 180 thermostat" thread but I wanted to open up the question with more detail. I have attached a picture of a thermostat that has been drilled (apx 3/16" or so) and there is only one hole. I have read where some have drilled 2,3, or even 4 holes of 1/8" or 3/16" in diameter.
My first questions would be, how many is needed and how many is too many?
My understanding of the hole(s) is to allow the air to bypass the thermostat during the initial startup to "burp" the coolant system. But, once the air has been purged from the coolant system, what effect do these holes have on the cooling system?
It appears that coolant can pass thru these holes when the thermo is closed due to the pump pressure. Does this affect the cooling system? With our intakes designed with vertical thermo holes, is there enough coolant pressure to allow a steady stream of coolant to bypass the thermo with the weep hole(s) added?
I have already bought a Stant 195 thermo to swap out my 180 unit. Now I am just trying to understand the goods/bads of added the weep hole(s) before I start drilling.

Thanks

5370170-thermo2.jpg (13652 downloads)

1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)