give nissan a call or swmotorsport

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Nissan

drove 16km each way from beacon hill to crows nest.. you'd think the car would 'heat up' by then.. alas no.. spluttering the whole way there and back!

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OK, firstly the Datsun engine has NOTHING in common with the Morris engine & even the most cursory comparison will reveal thet fact.

Secondly, it's the thermostat that controls the temperature of the coolant in the cylinder head.
There is NO back & forth flow in the lower radiator hose, the flow is simply a pump assisted thermo siphon principal.

Water that is cooled in the radiator decends while the water in the block & head is being heated & it rises. The pump keeps the flow going from cylinder head to radiator top tank, down through the core into the bottom tank, then into the lower hose, then into the block, then up to the head, past the thermostat & round & round she goes.

The thermostat restricts the rate of this flow & even redirects it back into the block to ensure quick warmups. The radiator can be from a Mack truck & it would make no difference to the engine.
The cool water from the radiator that is passed into the engine is exactly the same volume as the heated water that the thermostat allows out of the head & the temperature balance is well regulated when the thermostat is of the proper rating & is working properly.

As for the rough running, well that quite possibly has nothing to do with the coolant temp.

Most 1200's use an exhaust heated inlet manifold. It heats a small area of the inlet manifold directly under the carb & any fuel droplets that are too big to make the 90 degree turn in the manifold will hit the floor of the inlet manifold under the carb. This is the bit that is heated remember.
This liquid fuel is quickly turned to fuel vapour by the heat & drawn into the engine to be burned.

It must be remembered that it is only the fuel vapour that burns in the combustion chamber, fuel in liquid form does not burn & is passed out the back as "unburned hydrocarbons"

Lets add some extractors. Now we no longer have a source of heat to vaporise the fuel in the manifold.
The carb mixes the fuel & air in the right proportions but a significant percentage of this fuel is now passing through the engine unburned, which means that the remaining burnable fuel [vapour] is much less than it should be & the combustion chambers see a lean mixture.

Result? Power is down, & since more throttle is needed to restore power, fuel consumption goes up while driveability goes to hell.
See? Aren't extractors a wonderful thing on an otherwise stock engine?

This is why manufacturers switched to water heated manifolds. A much larger section of the inlet manifold can be heated & to a much more controlled degree.

The exhaust manifold can also be designed for better flow without he need for flapper valves etc.

So in winter, standard road going cars with carburettors need MANIFOLD HEAT to overcome the two refrigeration effects that occur at the base of the carb [on the inside] these being
1. Latent heat of evaporation. [huge heat is extracted from the air & fuel at the point of conversion from liquid to gas]
2. Temperature drop at the point of pressure drop. [this happens just under the throttle butterfly where atmospheric pressure is on one side of the butterfly while manifold vacuum is on the underside of the butterfly]

These two principals can be demonstrated by
1. soaking ones hand in petrol on a cold windy day, then hold it up in the wind. Brrrrr
2. Pump up your home air compressor to full pressure & allow the temperature [of the compressed air] to cool down to atmospheric temp, thn open the drain cock & watch the ice form on it as the air passes from high pressure to atmospheric pressure.

Exactly the same principal.

How do we fix these?
1. Fit a serviceable thermostat, new or used, genuine or not, just as long as it is serviceable.
2. Heat the bloody inlet manifold. It matters not how you do it but refitting the standard exhaust manifold would be a good start.
Smoother running, better driveability, more power & improved fuel economy should result.

Now you know why later cars had a hot air inlet system on the air cleaner too & they worked a treat.
Covering the lower half of the radiator will mean that the air passing through the core will be heated more & it's this hotter air that is being sucked into the carb that will provide vetter vaporisation & a small improvement in performance.
I did this with my 1200 ute many years ago & in sub zero air it was an advantage.

Damn clever those Datsun engineers, a damn sight smarter than most of us yet we keep ignoring their wisdom & we keep getting it wrong.

My dead stock 1200 Coupe starts first time even when the car is encrusted with morning ice. I just let it run at about 1000 rpm for a few minutes to let it get the chill out of its bones & with the heater on the ice on the windscreen quickly melts away.
By the time I can see clearly we are good to go & full performance is available after only a few miles.

Gotta love those Datsuns.

Wow.. All I can say is thank you.. That is the most informatve post I've had on this forum so please know I do appreciate the time you took to write it..

With regards to getting a stock manifold back on there.. What would be involved considering I have extractors.. Would I need to get a manifold and gasket and then get a new exhaust or would I be able to use part of my exhaust already?

So i'd keep the carb manifold and get rid of the extractors and replace them with a stock a12 exhaust manifold? on the tech wiki there are SO many choice.. how do i know which manifold is right.. the engine is a late model a12



Can you still buy manifold gaskets etc from supercheap or something?

now time to find a stock manifold that will do what is required..

just wondering if anyone has one for sale?

Cheers
Tom

what is the style /pressure of radiator cap? is it the same as a 1200 one? pressurised fluid has a different boil/freeze temp.
as for the cardboard, the sunny truck guys in Japan use adjustable alloy plates in front of the radiator to get some heat in(mind you it was -5deg during the day).

Hey disco bob yep same style

I think I'll get rid of those extractors and go with the standard manifold if I can find one suitable!

wow Dodgeman i actually feel dumber having read that misinformed load of monky spunk.
are you shour that your not the mechanic raping his wolet.

Dodgeman is correct, the Datsun A-series engine is no derived from the Austin. The Datsun C engine of 1957 was the Austin-derived engine. Nissan had licensed Austin patents back in the 1950s.




thomen, all A-series engine have the same exhaust bolt pattern. Exhaust manifold and extractors from A10 to A15 bolt on the same. But the exhaust pipe side varies, there are three kinds.

You can fit a hot air tube to extractors. You don't need a cast iron manifold. The hot air tube is to warm the inlet air -- not the engine coolant. Different purposes.

In any case, the engine running cool is not caused by extractors.

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Perhaps you could point out, in dot point form, each & every error in my post, along with the correct reply that I should have written & we can all be enriched by your giant intelect.
Learning to spell will lift our view of your educational standard & will help with your credibility.

Thomen

I have your e-mail & have replied.