I have a 92 YJ with a V8 (5.7 Chevy) conversion. My engines overheats on freeway drives, I have no problem trail riding. I have an aluminum radiator with 737 sq in of cooling capacity and 16in electric fan w/ shroud. The engine is rebuilt with 3000 miles on it. I have changed out the thermostat, I have checked the water pump for flow, I even took the heads off and had them checked. I have read all kinds of threads on different things to do and check and my problem still persists. Anyone have similar problem and had it resolved? I'm thinking of going to the mechanical(clutch) fan to see if that might help.

You have an air flow issue. Check for of the aftermarket suppliers for louver vents for hoods.

I am guessing that you have added under body armor. That has a tendency to trap heat by disrupting air flow with a result more hot air trapped in the engine compartment.

The simple fix is to add louvers to the hood to vent out the hot air.

BTW, I'm not a big fan of mechanical/clutch fans. I had one come apart on me that took out my radiator and bent the fan blade.

The electric fan should be fine.

Your radiator should be fine provided the aluminum radiator is mounted on isolaters to keep vibrations to a minimum as aluminum does not flex as well as brass.

I also added a Poison Spyder hood louver and a separate trans cooler, already. Believe me I have read all kinds of info and did what was recommended, that is why I am baffled as to this condition. There is plenty of open area around the engine to allow heat to dissipitate.

I'm thinking you still have an air flow issue. Do you have a winch in front of the grill?

What type of under body armor do you have? You can enclose enough to change airflow characteristics at high speed.

You might try a test drive with the hood off.

What about type of gas?

Do you have ac?

The electric fan should provide a consistent air draw through the radiator without regard to speed. With an intact shroud, you should be good to go. Replacing mechanical with electric is common to address heating issues.

You didn't say which year of engine.

Another thing...

What about your exhaust system? There is a wrap you can put around the manifold to reduce radiated heat. I have used that wrap on exhaust manifold of a 454 in a motor home to solve heat issues.

Also, if your exhaust manifold has any obstructions you will not get hot gases out effectively.

My winch is mounted in the front and it probably obstructs about 1/3 of the air flow. The engine is a '98 Vortec w/o ac. I am thinking/guessing that at high speed the electric fan running might act as an air dam blocking(?) the air flow through the radiator.

high probability.

The winch is going to obstruct a certain amount of airflow.

Under body armor, especially oil pan to t-case covering will impact air flow.

Electric fans are great to give a constant air flow without regard to engine speed.

Mechanical/belt driven are (IMHO) mechanically more reliable. But, their air flow varies with engine speed. I'm not a fan of clutch fan assemblies after having one come apart and taking out my radiator.

Very well could be the electric fan is not moving enough air. Is there a rated CFM of air flow for your fan? Can you get one that is larger CFM??

First a question.
Does the coolant leave the system? Or does the gauge simply register hotter than you like? If the coolant does stay in the system the engine is NOT too hot.
So what makes an engine run hot? A too low temp thermostat will cause the FLOW thru the radiator to be so fast that the coolant cannot be cooled enough and slowly builds up temperature that can lead to boiling out the coolant.
A too large pulley on the coolant pump can slow the pump down and lead to low flow thru the engine.
The fan can have too few blades or turn too slow, causing low air movement thru the radiator.
Lastly I have seen poorly modified Jeep sixes overheat from retarded timing at hi-way speeds. Is the timing advance working as designed on that Chevy?
Big Jim

The coolant does not leave the system other than the overflow reservoir. The pump pulley is the OEM for the engine. The thermostat is the 190 called for. I don't know the cfm rating of my fan(16"), but thinking of putting a larger one. I am using the original temp gauge, I think they put in a new sending unit? I looked at the front end again and the winch only covers 1/4 of the grill. Thank you for your input.

The engine can withstand much higher temps than the coolant can.
If the coolant isn't boiling out then the engine temp is Ok!
Too many times folks look at the gauge and think it should be registering a little bit more "over there" and get panicky.
If a larger fan will fit on there then by all means go for it.
But don't get worried until the coolant starts leaving.
And the 190* thermostat is correct for most if not all of todays engines.
Big Jim