my 68 Charger has a problem with overheating after 20-30min of around town driving. It's ok on the highway, but tooling around the burbs it gets hot, up to 230*

440
alum cross flow rad
2 elec fans always on
shroud

with my infrared temp gun the intake was 250, front of each head 230 top rad hose 200, bottom rad hose 145, driver's side water pump housing 200

seems like the rad is working?

how big is your rad?

Yes the rad is working cuz it is good at speed. If your timing is in the ballpark I'm thinking not enough airflow from the fans.

Based on you information, your electric fans are not moving enough air through the radiator at lower speeds PERIOD!!!

More info is needed but again your description indicates inadequate air flow

26" 2 core alum cross flow - universal.

How much temp drop should I expect across the rad?

same type of rad i have except its a down flo.I took my dual spal fans off and went back to a stock fan and shroud.temps went from 220 in traffic to 190 and thats on a hot fl. summer day.

Yep.

There you go.

Also the universal radiators do not fit as tight to the body radiator support. Fill in the gaps with closed cell foam.

I had problems with my Ram Van running too hot. I used a OEM twin electric fan setup from a 2000 dodge intrepid. At the time I read somewhere these flow more CFM than any other fan setup. I still was having an issue, so I used an old trunk weatherstrip to go around the entire perimeter of the shroud. This made a positive seal up against the radiator and forced all the air going through the fans to be pulled through the radiator. Problem solved.

I had pretty much the same problem with my roadrunner, especially if I got a couple red lights.I didn't have electric fans though.
I put a 160 thermostat in, only thing that seem to help.The only time it starts to get hot is if I'm stuck in traffic but not over 200.

would you try a fixed 5 blade or 7 blade clutch? I found both in the shop and will take back to Chicago to try.

I have a 7 blade, flex a lite fixed blade, on my 68 Charger, works great, 512 cid,cold AC in Southeast Texas, it gets over 100deg here, my car will run 180ish all day long.

I had the right spacers to put the 5 blade fixed on and it's dramatically better but not solved. It takes longer to heat up, but it traffic jams it will move off the t-stat. Going down the road it does cool itself off better.
I need to seal the top of the rad support to the rad, the sides are now sealed, they weren't before.

Probably going to try one of the clutch fans, I've ordered the spacers

Seal the radiator to the yoke opening top/bottom and sides with adhesive sided foam strip so it stays in place and doesn't get blown/sucked out and get a shroud on it as well that encases at least 50% of the fan blades width, with no more than 75% of the fan buried in the shroud, cooling basics 101

ya, I can't find a shroud for the universal cross flow rad with a mech fan. Summit has some very generic metal that they sell as a make your own kit, might have to try that.

Or better electric fans. Do be aware that as the airflow on better quality fans goes up, so does the price and current draw on your electrical / charging system.

It's very hard to beat a good stock factory set up.

1971 Challenger 430ci Hemi stock factory 3 core rad, cores are clean, 7 blade Chrysler fixed fan no clutch, shroud, mated water pump and housing, 160 quick flow thermostat, car runs at 163 degrees all day long no matter what I am doing or were I am driving or how hot it is outside. Timing has a big effect on temp also.

In our loft I found a new thermal clutch and 5 blade. I put the 7 blade fan on it and low speed cooling has improved even over the fixed fan. Bought a universal fiberglass shroud but didn't fit. Still will do that eventually but now the car tolerates 90* commutes with the AC on. Still heats up a little bit but cools off quick

I have a brother whos 440/Duster needed a fan shroud. Universal aluminum radiator running hot at stops....He was able to make one of these work with trimming and cutting. Chose the one closest to what he needed and fabbed it till it fit and functioned. Functions very well.

http://www.allstarperformance.com/product.htm?prod=313

I tried for 6 years to resolve an overheating problem with my 1969 383 Roadrunner. I tired everything, timing, different carburetors, different water pumps, thermostats, fan blades (flexible blades and even a Super bird fan), coolant conditioner, even a Max Cool radiator from Glen-ray radiators. This was a matching numbers show car so aftermarket items were not really an option but I did try a few. My position was that this car was built to cool on the equipment Mother Mopar gave it in 1969 (Arizona car) and I just need to find out what the problem is. After several years I took the car to a reputable race shop, had the engine torn down to look for a blockage or core shift or something. In the end nothing adverse was found but still the engine wouldn't cool. Never did find the problem. I have attached some of the "threads" related to my overheating problem. My hope is that some of the suggestions provided by Moparts members to help me solve my problem will help you. I have included 3 threads but there are more if you want to search under my user name. Good luck.

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/1451739/1.html

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/1026768/1.html

https://board.moparts.org/ubbthreads/ubbt...tml#Post1631535