Are there distinct differences between the two types of radiators as far as one style is more efficient cooling over the other ?

no!

I have zero research backing up my theory but here it is.

Tall radiators like our Mopars have and big trucks have downflows to keep the tubes long.
Short and wide radiators would have extremely short tubes if they flowed downwards.

I don't think you'll see any real-world difference in the types of rads you'll use in our old cars. I run a crossflow and like it just fine.

Read this.

http://www.arrowheadradiator.com/overheating_causes_and_cures.htm

I read it and didn't see a single thing about downflow or crossflow. Did I miss anything?

In general if the radiator is a single pass heat exchanger it doesn't really matter what direction the tubes run. I believe that radiators had vertical tubes because they fit in the grilles better and could have the radiator cap at the top where it was most easily accessed. When Detroit went to the "longer, lower, wider" mentality the radiators became lower and wider to fit under the hoods, thus the crossflow radiator.

R.

..a cross flow will lose cooling from the top few rows unless you have a coolant recovery tank.

Given the same area of fins and capacity of tubes the difference is neglible. What will make a difference is the style of fins.

What makes a HUGE difference and why I'd never get another downflow if I had the choice is that the downflow tubes will plug up a whole lot sooner than a crossflow will. The crossflow will lose one or two tubes at a time. The downflow is losing whole areas where sludge is gathering.

My 6 year old Dodge Durango lost major cooling ability last summer. If you put your hand on the rad. fins it was obvious that several sections of tubes were cooler and limited. In the span of owning at least 3 crossflow style rads in off brand cars.....I've NEVER had to replace a radiator due to blockage in 20+ years.

Don't know if this has been mentioned or not, but cross flows are more prevalent these days due to lower hood lines. Just can't make a down flow work in these situations.

In a "square" package though, there should be little difference in cooling capacity all else being equal. You will lose cooling capacity with a cross flow without an expansion tank that will keep it full and coolant flowing through all rows.

How about we throw a 26" stock steel downflow radiator out of a late 60's B body and a 26" after market aluminum crossflow radiator into the mix. Which one is superior...?

If the area of the exchanger (and other factors, of course) is held equal, a greater quantity of short tubes will outcool a smaller qty of long tubes.

Cooling occurs due to the difference in temp between tubes and airflow, so you will achieve greater heat exchange thru teh 1st 1/2 of a tube compared to the 2nd 1/2.

Copper/brass have better coefficients for heat transfer, but tube & fin design/layout in a modern radiator can make up for decreased heat transfer of aluminum (compared to an 'old' radiator).

Any new rads I buy in the future wil be ...crossflow DUAL PASS !

This spring I'm going to replace the stock type 26" radiator with an aluminum (Griffin) crossflow. This thread has been very informative.

crossflow cools better.....looks uglier but cools better

Are we forgetting one thing that heated water will flow to the top faster in vertical tubes. So. the bottom has cooler water for the engine.

Cross flow units have the advantage of having the radiator cap on the low pressure end of tubes so that a high volume water pump that builds additional pressure in the block (which is a good thing as it raises the boiling point in the block thus minimizing localized steam points) will not blow the seal on the radiator cap.

Further wide rectangular aluminum tubes provide better heat transfer because more surface area is exposed to the air flow as opposed to the oval tubes that must be used in copper/brass units in order to maintain strength. In these units the air flow tends to skip across the high points of the tubes instead of following the contour.

And, the obvious, the wider tubes don't plug up with precipitates/sludge as easily as do the small tubes and the radiator weighs less as a bonus.