Thread: 4.6 engine questions

4.6 with Thor inlet or the common plenum chamber (trumpets)?

The Discovery II has a 4.0 with coolant operating temperature at around 97-98 Deg C, and presumably the 4.6 version found in the P38A will be running at the same temp.

I would be running the 4.6 as cool as possible, 75 degree? If you can figure out a way to trick the ecu into thinking this temp is 20 degrees higher - you'll be sweet.

High temps and alloy motors aren't a good thing.

Make a small hose tee (threaded 1/8 NPT with 5/16 nipples) to install into the bleeder line to the top tank of the radiator. Place it near the thermostat and you will read engine temp no probs. I would suggest an 80C thermostat is a good compromise between engine reliability and economy. 88 to 90C is best for economy, 75C is for brute force. My experiments indicate about 10% economy increase with every 10C rise in engine temp.

blitz wrote,...

Does anyone know what the optimum operating temperature of the 4.6 is?

Yes it very much depends on whether your engine is running carburettors or fuel injection.

I run twin SU carburettors on mine with a 74 degree thermostat.

Ron.

It's got the normal 3.9 inlet manifold on it and it is injected.

I dont want to use an adjustable thermostat I would rather get one from a car that has electric fans and adapt it to fit. There are hundreds of them I just need the right thread size and I will go fromt here.

Originally Posted by blitz

It's got the normal 3.9 inlet manifold on it and it is injected.

I dont want to use an adjustable thermostat I would rather get one from a car that has electric fans and adapt it to fit. There are hundreds of them I just need the right thread size and I will go fro mt here.

A fan temp switch wont control the engine temperature (well not directly or properly).

To find the correct temp for a fan controller setting - i'd find out the temp of the return water in the lower rad hose during a 40+kph cruise then add a few degrees. This way the fans wont turn on during normal driving, just as needed. I'm guessing 50 degree ish??

Originally Posted by Hardchina

A fan temp switch wont control the engine temperature (well not directly or properly).

To find the correct temp for a fan controller setting - i'd find out the temp of the return water in the lower rad hose during a 40+kph cruise then add a few degrees. This way the fans wont turn on during normal driving, just as needed. I'm guessing 50 degree ish??

I'm just going to fit a set fan temperature sensor switch in the same place as fords do, as I am using a ford electric fan assembly, i figure if ford are happy doing it that way who am I to argue - I just wanted the optimum running temp

Being fuel injected, is not 88 degrees C the typical operating temperature for such engines?

4.6 or 3.9, running the latter manifold and electronics would requre that the engine run at the temperature commensurate with that system,..would it not?

So that would be the minimum temp to run the engine for the system to function correctly, so running within a window of say 88 to 92 degrees at all times for fuel economy and engine longevity.

No point in going hotter than you need to.

Ron.