For every pound of pressure the cap has, the temp goes up 2 degrees. A 13 pound cap will bring up the radiator temp 26 degrees. A lower pressure cap has helped me in the past. A 9 lb will make it 18 degrees. Maybe this will help some. I have a 4 row high efficiency desert cooler in my full size van with a 350 and it runs about 190-195. Even with the a/c running and a new factory 195 stat. My pick up with a 350 has a 3 row standard 7 fins per inch and stay exactly 195 and barely moves when going up long hills. Its got quite a bit of scale in it and its the original 87 radiator. Its going to get a new 3 row 14 fins per inch core this week before putting in a new modified 250 inline six. Will cool almost as much as a 4 row without spending a bunch more for a 4 row and get little more cooling. Standard GM rads usually are 7 fins per inch as per the radiator shop where I get mine. More rows and more fins per inch do make a big difference in cooling power. Aluminum rads cools more effieciently and more PRICEY! A 2 row with cool like a 3 row. A 3 row aluminum should really do the trick. Brass does not cool as well as aluminum. I put a new brass radiator in my Bravada (S-10) with the 4.3L and it had a new water pump and thermostat and with the a/c running it would run hotter than I would like it. I replaced it with an aluminum and that solved my problem. I learned these things the hard way. I just hope this will help some plus with all the other suggestions posted here. Henry
