I just attempted to replace my 3 core with a 4 core but obviously need a new top plate and shroud. I put the Stop Overheating additive in the radiator when i put things back together and now my car is running even hotter. It only ran hot before when the air was on in the daytime. Wht would this stuff make my car run hot?

"Fixing" your car by pouring some chemical solution or liquid into the: crankcase/radiator/battery/transmission,etc. etc. is a fantasy. Here's a good article or two that might give you some ideas:

www.troubleshooters.com/tautomot.htm (http://www.troubleshooters.com/tautomot.htm)

Good luck!

My $0.02

Actually the last poster has it right, but in some instances it really depends on what is making your system run hot? For example, the formation of hotspots and/or cavitation can be cured with some surfactant additives such as WaterWetter. WaterWetter also helps coolant absorb heat faster. Combined with a higher area radiator and/or bigger fan will improve system efficiency measureably.

But, the real question is under what conditions is the system running hot? At cruise or at idle or both? Your answer to this will be very important to the cure.

Usually a system that cools at cruise and not at idle or slow speeds has an airflow issue. This means fan system, shroud or both?

A system that cools okay at idle or slow speeds but overheats at cruising speeds can be a collapsed lower hose or a too lean jetting condition.

A system that has overheating issues with both has something inherently wrong with the mechanics of the system such as a plugged radiator or weak pump or sticking thermostat.

I just replaced the stock radiator in my '64 wagon with a 4 core Desert Cooler. I have Vintage Air and added a trans cooler in front of the condensor. I am seeing temps of 5 - 10 degrees cooler. (190 morning temps and 200 -205 afternoon temps with a/c on at highway speeds)

I started the car up in the drivway and let it high idle for a few minutes. It ended up puking coolant which it has never done. I ended up draining the radiator and flushing well and added water and antifreeze and now temp is back to normal. The garbage i added to the coolant to cool things down is what made it hot! Dont buy "Stop Overheating from Discount Auto Parts" its junk,. Now im even nervous to try Water wetter.

Blaster and others, Cooling problems are a booger bear to solve and its normally a trial and error thing. Start with cheap and simple and go from there. Two points I didn't see mentioned in the previous posts were the air dam thats under the front bumper of many A bodies that directs air to the radiator at speed. These suckers get knocked off over time for various reasons. Also check your heater at idle, under the best of conditions the water pump has trouble pumping water to the heater core. When the impellers on the pump go south you may not get much heat after a few minutes of checking it at idle.