Help please: What, if any, are the impacts of varying tube ID between the engine, water pump and radiator?

I want to run hard lines from the engine compartment to the front trunk. They will be protected and the plan should eliminate any concern about cabin heat. Here's what I'm looking to better understand:

As I understand it, I can expect sufficient flow from -16 AN fittings and hose. This has an ID of .089.
A 1" .049 wall 5052 AL tube has an ID of .902.
The radiator has inlet/outlet fittings that take a 1.25 ID hose.

Assuming I hook all this up, are there any odd or problematic things that happen when the 1" line dumps to a 1.25 radiator opening then upon exit, flows from 1.25" back into a 1" line?

Apologies if this is rudimentary. I'm new to H2O cooling...



Thanks,

Chris

I've seen little difference between 3/4" and 1" I.D. tubing fitted with hoses compatible to the outside diameter of the tubing. I've also not experienced any issues with the radiator outlet reduced to a smaller size line. This is with a 355 SBC with electric water pump, A/C and summer city driving in Tucson. The biggest effect I've seen has involved changing how the air moves through the radiator, such as using an air dam under the car to increase pressure ahead of the radiator and help reduce hot air recirculation out of the wheelwells.

Smaller diameter hard lines shouldn't be a problem, I think the 996/986 do the same thing. The actual ID of the engine outlets is close to 1" anyways.

Some of the other things has me concerned. Can you elaborate on your design?

Let me know what, in particular, if this doesn't clear it up.
A couple things. If a small drop in ID isn't a problem, I'll up the wall thickness.

If you've seen my build thread, you'll see I plan essentially a complete tunnel update.
The current plan is to replace the tunnel with a pair of 1.5" bars that run from the lower fire wall to the front of the car. The top of those will be skinned w/sheet metal but I'm planning to remove the floor under that section. So essentially I'll have a 1.5" tall tunnel that's open on the bottom. That will covered with a removable, ventilated cover that is part stiffening element, part bash plate. The underside of the car/tunnel area will be sprayed with something like LizardSkin or other heat/sound barrier.

Critique away!

And thanks in advance for any help.
Chris

Sounds like a great idea...build it.

T