when to use a dual pass radiator

[user-23911]

The only restriction to cause pressure from the pump, that's the thermostat.
That allows the block and head to increase pressure while keeping the radiator on the suck side.
When the pressure cap vents, that's usually due to the HG leaking.

[Warp Speed]

The better radiators have vertical tubes and flow top to bottom.

And why is that?!?

[user-612937456]

The better radiators have vertical tubes and flow top to bottom.

And why is that?!?

Agree all I can do is speculate as to why but I've had a couple experiences changing from a downflow to a cross flow curing overheating problems. My theory was the downflow was letting coolant move to the radiator too fast we went to a cross flow the coolant spent more time in the radiator core I guess this could be similar to putting a restrictor in thermostat housing too slow in the flow

[user-612937456]

The better radiators have vertical tubes and flow top to bottom.

And why is that?!?

Agree all I can do is speculate as to why but I've had a couple experiences changing from a downflow to a cross flow curing overheating problems. My theory was the downflow was letting coolant move to the radiator too fast we went to a cross flow the coolant spent more time in the radiator core I guess this could be similar to putting a restrictor in thermostat housing too slow in the flow

[statsystems]

The better radiators have vertical tubes and flow top to bottom.

And why is that?!?

Agree all I can do is speculate as to why but I've had a couple experiences changing from a downflow to a cross flow curing overheating problems. My theory was the downflow was letting coolant move to the radiator too fast we went to a cross flow the coolant spent more time in the radiator core I guess this could be similar to putting a restrictor in thermostat housing too slow in the flow

The coolant moving too fast through the radiator theory was wrong when I first heard it in 1979 and it's still wrong now.

Flow does the cooling. Slowing down flow causes the coolant to stay I'm the block longer and pick up more heat. It is thus harder to cool.

Stewart components and Evans coolant have some very good tech coverage of this.

[ptuomov]

Faster the flow, better the cooling. This is for two reasons. First, faster the flow, greater the turbulence and thus heat transfer. Second, faster the coolant flow, the greater the average temperature differential between coolant and the wall at both ends. The cost of the faster flow is more work done pumping the coolant.

In terms of dual pass vs single pass radiator, I can see that there's one arrangement where dual pass really makes sense. It's two cores sandwiched such that the hot coolant goes first to the rear core and then second to the front core. This way, you'll get a reasonably high and stable temp differential at both first and second pass between the coolant (air) and the fluid to be cooled (engine coolant).

I don't know this, but I'd guess that vertical flow radiators are better than horizontal flow radiators if there are a lot of small gas bubbles in the coolant. I would imagine that those will come out better in a vertical flow radiator. But that's a pure guess.

[pamotorman]

to have good cooling you need at least 30# of pressure inside the block to make sure there are no air pockets not filling with coolant. if the water pump is in cavitation at high RPMs the pressure will not be there and you will have heating problems and possible detonation. back when only stock pumps were available I removed every other fin from impeller to fix this on circle track engines.