What is a safe water temperature?

[Bob Bidonde]

160F to 180F is safe. In the order of hottest to the coolest, the cylinders are Nos. 4, 3, 2, 1. No.4 is the hottest because most of the coolant bypasses it.

Be mindful that as you load the engine (accelerating; climbing hills), its operating temperature increases.

 

[Kurt in NJ]

160F to 180F is safe. In the order of hottest to the coolest, the cylinders are Nos. 4, 3, 2, 1. No.4 is the hottest because most of the coolant bypasses it.

Be mindful that as you load the engine (accelerating; climbing hills), its operating temperature increases.

I recently did some temp checking after reading about these temp differences and I didn't get the results you say---perhaps it is because I have a thermostat---original radiator last cleaned 30 years ago, no problems with coolant loss (level wasn't checked for test)
cyls 1 2 3 4 coolant inlet
1 mile drive 166 170 164 167 145
idle for 1 hour 196 197 200 204 165
5 miles 189 184 183 182 160
20 miles @ 50+ 183 180 175 182 159

oil after 20 miles 170
readings taken at side of waterjacket below headgasket

 

[Tom Wesenberg]

I had readings similar to Kurt's when I shot the temps a year ago. After a 20 mile drive my rear end temp was less than 10 degrees over air temp.