Direction of Coolant Flow with 1600 Motor

[SP3]

Seeking understanding on how the coolant recirculates through the R16 motor - specifically which radiator hose is carrying the coolant before heat exchange in the radiator and which one carries the cooled coolant back to the motor. Does waterpump move cooled or heated fluid through system?

Also with temperature reading, what is the understood temp where the motor should be shut down to cool off to avoid warping head.

With cold starts in morning, what is the advised warm-up temp before pulling off and driving - when thermostat opens at 160? (running 160 t-stat). Car resides where minimal choke is needed to start - only 1 hooked up.

Getting some guard rails for newby to Roadsters for safe engine operation until further bulletproofing.

[Florida Roadster]

Most radiators run top to bottom and I would assume the R16 is the same. The thermostat resides on the top front of the engine and when sufficient temperature opens it up, the coolant flows up and through the top hose to the radiator. Then coolant flows down, with gravity, through the radiator and returns to the engine via the bottom hose. Others chime in and correct me if I'm wrong on the Roadster.

[Bwk2000]

Jeff is correct.

General Flow: Bottom Rad Hose > Water Pump > Block/Head > Thermostat > Top Rad Hose to Radiator
Manifold Flow: http://kendo-usa.org/datsun/manifoldvalve.pdf
(Diagram courtesy of Curtis)

As for the operating temps, with a 160 thermostat, you may still see 170-180 temps depending on the day.
I typically run a 192/195 thermostat (it’s cooler up in these parts) and will see 200-210 temps.
If I was getting anywhere near the 240 mark, I would shut it down to save the head.

[Gregs672000]

I think the red line for temp was 240 on the gauge. Not a bad idea to confirm temps with a laser as the gauge can vary some with the inline regulator that controls temp and fuel gauges. The engine typically likes around 180-190 as that's what I think it was designed to run at. I used to warm up my engine for several minutes with carbs as the engine was kinda high strung so I preferred to wait (not much wait now with EFI). The chokes are there to add a bit more fuel when cold and bump up the idle a few hundred rpm when working correctly (which often they are not). They should make the car driveable when cold, and it won't hurt the engine to do so. I ran no chokes on mine before the conversion to EFI (Mikuni type carbs).

I gather you are trying to advise folks who may be new to such manual (choke) set ups. Advise them that the car will be a little temperamental when cold, so be easy with the the throttle (don't mash the gas, or worry if she pops some and hesitates until it's warm. Don't expect it to respond fully when you're turning onto the street/into traffic when cold... it might hesitate so add more space between cars) and that the engine can "load up" some when it's warm AND the chokes are still on (too much extra fuel, will run rich and "chug"). After a few drives they will understand!

[SP3]

Thanks all for replies. Very helpful.

Yes Greg trying to keep him from blowing a head gasket or warping head.

To add more accuracy/reliability swapping out OE electric gauges for mechanical water temp and oil pressure thus question on the radiator hoses and which is better choice. Mounting pickup there to get away from header heat with stock sender location in head.

Once he learns the ropes on “care and feeding” agree he will love the experience. Intention is to use as a daily driver.

[Gregs672000]

It's best to pull temp info from as close to the head as possible from what I understand. For my EFI, I was directed to put the sensor before the thermostat, and ended up tapping into the port opposite of the stock temp sender (on a U20, which is different from an R16 set up). You'd be fine pulling temp from the upper hose no problem, pretty sure they make an adapter that adds a port for the hoses.