Cooling issue on highway

RustyRatRod said
And for the record, my slant 6 has over 175PSI cranking pressure so it generates some heat for a six.

My 340 is about the same, 175-180 cranking PSI.

And for the record I never said a mechanical fan can’t work. I just said it’s less efficient.

Like I said before, I’ve got no problem with mechanical fans. I just hate all the guys that say electric fans can’t work because they set up a lousy system because they have no idea what they’re doing. They work great if you use the right fans and set up the system properly.

George Jets said
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.

Yeah that test won’t tell you if you’re moving enough air to keep your engine cool. It takes VERY little airflow to stick a piece of paper to your radiator.

Now if your fan can’t even do that it definitely won’t cool your engine. But just because it can hold a piece of paper on the radiator doesn’t mean it will keep your engine cool by any stretch of the imagination.

What would tell you is the CFM rating for the fan, which is readily available for most electric fans and should be available in a cfm vs rpm graph for any mechanical fan worth the effort.