Topic: Thermostat hole size.


wlobb    -- 04-26-2025 @ 6:57 AM
  Hi guys, I'm replacing my 180 degree thermostats with 160 degree after I flush the block. In the past I've drilled 1/8" holes in them at 12 and 6 o'clock. I've seen some guys go as big as 5/16". I'm thinking 3/16". Does anyone know what is too small and what is too big?

Thank you, as always

BIll


52flatv8    -- 04-27-2025 @ 5:02 AM
  Hi Bill. I just had one 1/8th inch hole in my 180 stats and the 8ba ran 185 most of the time. Actually replaced 160 stats with the 180s and it ran cooler after drilling the 1/8 holes. Hope this helps.
Mike


wlobb    -- 04-27-2025 @ 5:12 AM
  Hi Mike, thank you! yes, this helps a lot i appreciate the feedback!
Bill


FordFreak    -- 04-27-2025 @ 5:37 AM
  For decades now, I have always drilled mine 1/8 in. Seems to be the most common size, always worked well for me. Out of curiosity, why are you going to 160 'stats?


51woodie    -- 04-27-2025 @ 10:50 AM
  When I bought my '46 coupe , 59AB, it had 160 stats in it, but the were miss matched. I put new 160's in it, but it ran at 165-170, which to me was too cold. I switched to 180's, and now it runs 175-180. I didn't drill any holes in the stat housing. You don't say what year/model/engine you have, but if you are having an overheat problem, colder stats won't necessarily correct it. You need to have all the shrouds and shroud seals in place, to maximize the air flow through the radiator.


52flatv8    -- 04-28-2025 @ 5:35 AM
  I also wondered about 160 stats. My 8BA ran hotter with 160s than it did with 180s with the 1/8th hole in them.


JayChicago    -- 04-28-2025 @ 7:04 AM
  I've never heard a reasoned reason for 160 degree thermostats. Your engine will thank you for staying with the 180 stats.



carcrazy    -- 04-28-2025 @ 3:24 PM
  Use of 160 degree thermostats will give you a little bit more of a cushion on coolant temperature when climbing hills or driving in high ambient temperature conditions. If you want to drill a hole to ensure proper water movement before the thermostats open, you can drill one 0.125" hole in the non-movable part of the thermostat.


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