74C Thermostats

[Darkspeed]

Just in case anyone is looking for info or part numbers on the 74C stats as they are recommended as the performance option in place of the 82's and 88's

Quinton Hazel

QTH101 - Stat
QTH101K - Kit Stat and Gaskets

For 1.3 A series typically - Listed as a Summer use stat

There isn't an air bleed on the stat rim as such its just a groove in the seat so maybe worth drilling a 3 or 4mm bypass hole in the stat and placing at the top when installing.

Cheers

Andrew

[Paul B]

Just in case anyone is looking for info or part numbers on the 74C stats as they are recommended as the performance option in place of the 82's and 88's

Quinton Hazel

QTH101 - Stat
QTH101K - Kit Stat and Gaskets

For 1.3 A series typically - Listed as a Summer use stat

There isn't an air bleed on the stat rim as such its just a groove in the seat so maybe worth drilling a 3 or 4mm bypass hole in the stat and placing at the top when installing.

Cheers

Andrew

I ran an 80c stat in my Morris, but I had an electric water pump and rad fan. I can't imagine why you'd need a 74c stat in a 'normal' car, unless your cooling system was marginal.

[Darkspeed]

Generally because temperature robs power - good for economy but not much else - Anything above 70C and power drops off the hotter it is and the more the power losses -

The 74C stat is a compromise on a road car as the temperature usually settles about 4C over this.

Question is why would you run it hotter?

[katanaman]

Can you link to any sources that back up what your saying here? I agree with heat robs power but I didn't think it was anywhere near 70c. Also if your saving fuel your engine must be running more efficient and an efficient engine is a powerful engine. Or did you mean good for emissions?

[sidecar]

A 74 degree stat is a good idea on any of the larger RV8 lumps. I run one in my 4.6 and it runs at about 78 -82 degrees.

This could be an issue if you are running EFI!

Pete

[Darkspeed]

I did not write efficiency - but yep probably emissions as well

And my source for info regarding the temperature of 70C is David Vizard

Andy

[katanaman]

No it was me who wrote efficiency to qualify less fuel = more efficient = more power which knocks what you were saying.
I agree if you have an engine that is thermally fragile its a good idea to run it cooler though. I guess the only way would be to get back to back dyno runs at various temps.

[kiwicar]

From what I remember the Vizard temperature test was on a 1.6 (very) long stroke A series lump which was tuned to give about 115 bhp (in 1983 ish) from what I remember the engine produces maximum power with a head temperature of about 70-72deg C but it was run very rich as the petrol was not atomising well, you don't care how much comes out the exhaust with a race engine like this one I also remember it flooded below about 2.5K revs. He was running the oil very very hot otherwise the engine would pinch the pistons at the bottom of the stroke and partially seize.
He repeared it with a 2.3 pinto, to similar effect, but this time he put a slight taper on the bores to try and get over the bore pinching problem, one of his conclusions was that what was really needed was a split cooling systen, heads and block cooled seperatly and run at different temperatures.
The above would fit with some US megga power 5.0 ford turbo drag engines that seem to have extrawater feeds to (or from) the heads.
Mike

[topcatcustom]

Running the engine 10degs cooler would also no doubt help with the old liner slip problem- after all didn't that start becoming a major problem when Rover had to start using higher temp thermostats for emissions?! ..expansion rates of ally vs iron/steel etc...

TC

[sidecar]

Running the engine 10degs cooler would also no doubt help with the old liner slip problem- after all didn't that start becoming a major problem when Rover had to start using higher temp thermostats for emissions?! ..expansion rates of ally vs iron/steel etc...

TC

That's what I was getting at with my post, I just did not explain it very well!

In fact the block was only heated to 140-150 degrees before the liner was pressed in, so running it at 90 means that there is not much grip on the liner. The liners also lifted as the block cooled because they were not held down, Rover did not then push them fully home afterwards either.

My understanding is that they ran the lump hot and lean in order to get the old design through modern emissions tests. That in conjunction with less than good casting patterns and moulds resulted in whole load of problems!


Pete

[RoverP6B]

I run a 74 degree thermostat in my 4.6, which is fitted with twin SU carburettors. Depending on ambient temperature and driving conditions, coolant temperature will vary between say 74 degrees Cand 85 degrees C in most cases.

Engine oil temperature, as measured from the sump plug will also vary between say 75 degrees C and 90 degrees C in most cases.

On a country run averaging 100 to 115kph (60 to 72mph) fuel consumption will run anywhere between 24 and 29mpg. The best fuel consumption figures that I have achieved in all cases is when the coolant temperature is closer to 74 degrees C.

I covered 230km (144miles) today, returning to Sydney after having been away over Christmas. It is a route that I have covered on numerous occassions. Ambient temperature today was around 27 to 29 degrees C. In the car 37 to 42 degrees C Coolant temperature was pretty close to 82 degrees C for most of the time, and 27.5 mpg was returned.

Ron.

[Darkspeed]

which knocks what you were saying.

Well until I find advice to the contrary the 74C stat stays and D Vizard is a good enough nod for me.

[katanaman]

which knocks what you were saying.

Well until I find advice to the contrary the 74C stat stays and D Vizard is a good enough nod for me.

And of course your completely entitled to do that even although it would appear you have completely missed the point of his test.

[Darkspeed]

I'm alway open to new advice so if running it at 74(ish)C is a bad thing then please let me know.

I will also quote Bell from "Performance tuning in theory and practice"

"....... I have found that a water temperature of 70C to be ideal, from the aspect of best power and lowest bore wear.A side benefit of lowering the water temperature is lower oil temperate......"

He explains why 88 is used in production vehicles and the why's an wherefores of 70C if you want more detail buy the book

As for Vizard neither of the examples above is where my information comes from so you can keep your incorrect assumption regarding missing points.

[Paul B]

Generally because temperature robs power - good for economy but not much else - Anything above 70C and power drops off the hotter it is and the more the power losses -

The 74C stat is a compromise on a road car as the temperature usually settles about 4C over this.

Question is why would you run it hotter?

Hmm, so why does every car manufacturer in the world use a pressurised cooling system, that runs well above 74c?

How long before you have emulsion and goop in your oil if your motor never warms up properly?

I've always thought that heat is power, and sucking heat from your motor is just sucking power out and dumping it in the atmosphere.