Cooling issue on highway
And for the record, my slant 6 has over 175PSI cranking pressure so it generates some heat for a six.
If you are going back to the 4 blade fan, move it in closer to your radiator like 3/4" off the radiator, that will help to pull more air through the radiator without a shroud.
You can do the 9 x 11 paper test (or use a paper towel). Put the paper towel on the front of the radiator with the engine running, it should suck it up tight against the radiator.
This will show you if you have enough air being pulled through the radiator to keep it cool.
Was a good test when we went from the solid mount 15" silent run fan test fan, to the 18" solid mount silent run fan.
There was a huge difference of how much air was being pulled through the radiator between the 2 fans.
The 18" fan sucked the paper towel up tight to the radiator, to the point you could hardly peel it off of there.
Same tests work for the electric fan/box shroud setups to see if there is enough air being pulled through them.
