Running without a thermostat ok?

340demon said

worked for a major truck researce lab this is what we found the shroud is very inporant why the fan only pull air from the area in front of it with out one now the air hit the hot motor and some is forced back to the cornors of the rad. thus a heat problem with the shroud the fan pulls air across the hole rad the was found in wind tunnel test with smoke tracer beleve it or not it dose happen we also test with and with out, big differene

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Indeed. Fans will pull air from the area of least resistance. The engine compartment is also a very turbulent area. Air exiting the fan meets the engine, and can even meet higher pressure from the underside of the car and revert back toward the low pressure area in front of the fan. The radiator is a pretty big air restriction, it's like a wiffle ball.

When we add a shroud, the fan has fewer 'choices' of places to draw air from and will pull air through the radiator.
At higher speeds, the fan may not be able to evacuate all the air ramming into the radiator, so many shrouds have built in doors which blow-open at speed.

Another trick to help draw air through the radiator is to keep the area under the car and the engine compartment at lower pressure. An air dam can do this, which is why folks add them to help with cooling. Lowering the pressure makes the air want to get through the radiator to the low pressure area to fill it. Keeping a little 'rake' to the car can help too, but not always and rarely consistently.

An air dam and a shroud will usually help immensely. the shroud for low speed and the air dam for higher speeds (if your temp tends to creep up when cruising at highway speeds).