I have / had the same problem with mine....still havent figured out why it runs so damned hot, but I upgraded to a 3G alt, installed a Lincoln Mark VIII fan, 180 t-stat, straight water with 2 bottles of water wetter, Griffin 31X19 aluminum radiator and ended up with temps of 180-220 depending on the heat and the a/c.
I think that I may have problems with the a/c though. My belts are run like this:
And I am using a reverse rotatoion water pump.
The stock 351W fans are made for the standard rotation pumps...I tried that too when I first got the car out of my friends shop. I didnt make it a block before the thing was boiling over. If you use the stock 302 set-up you have to use the 302 fan. With a heavy duty clutch you should not have a problem with airflow.
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Engine:
1990 5.8 / Edelbrock Performer set-up
MSD ignition
Suspension:
Maximum Motorsports Caster-Camber Plates / Maximum Motorsports adjustable lower control arms / FRPP heavy duty upper control arms / Tokico Illumina Shocks and Struts / Ground Pounder Coil Over conversion kit front / Steeda cross brace sub-frame connectors /
Drivetrain:
Tremec 3550 trans / Steeda Tri-Ax shifter / Spec Stage II clutch and pressure plate / Spec aluminum flywheel /
5.8 in the hole