Hmm just buy a whole other A12 that runs, when you start buying carbs and thermostats and all that jazz plus paying for a mechanic to do it all then you might as well just buy a running A12 that RUNS.

Otherwise stop pissing about and shove a sensor up the tail pipe or get the thing to a shop that will dyno it and know what they are doing, the good old rolling road is very useful. The great thing about a Datsun is that they are cheap to run, but they are only cheap when they work and they can get just as expensive as any other 4cyl modern engine when they need to be repaired by a professional.

old-tin get a link up for this thread that you're on about.

And if you disagree with the previous comments with such objection then explain and clarify the errors and let us know what your theory is behind why Isuzu, Subaru, Nissan and Datsun (Mazda, Mitsu?) find it necessary to preheat the inlet manifold either via water/coolant circuit and or exhaust platform.

Look forward to hearing about it all because it appears I too have had it all wrong.

sorry but your not making much sense to me- he thought the problem might be associated to extractors- mechanic said to him:

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this make sense in regards to the thermostat not opening. nothing directly involved to the extractors, just an idea omen had.

im no mechanic but in cold eropean and even alpine regions in australin winters, they do restrict airflow to the radiator by blocking off the airflow- cardboard is just a rudimentary way of doing it.

ive had extractors on every datsun i have ever owend, never had this issue related to extractors, just issues with radiators.

personally try the cartdboard, if it works your onto something. if it doesnt,move on through process of elimination.

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http://www.morrisdownunder.com/forum/index.php

you forgot holden, ford, audi, volkswagen, bmw ext and as i have said for emissions..... as i have been told some of the more moden cars are controld with a vave during for the cold european climates.

i don't know of 1 single petrol marine engine(what i'm most familiar with) that has heated manifold's because it is not necessary, even when the water temp is below 0deg c thay run vary well with no iced up jets.
now why did the holden grey motor have no heated manifold?
and the first of the hoden reds have no heated manifold?
then the hr 186 has a heated manifold?
you guest it emissions, thay even sold a alternative manifold and thermo housing to piss the emissions crap of why? because the heated manifold poorly affected prformence. what do you think happens when you have a 80deg c manifold in 40deg c ambiant? thats right you carn't get the optomum fuel-air charge in the chamber, in turn restricting engine input and out put. piss it of faten up the mixture presto better overal engine. the turbo boys don't run intercoolers just for looks and the n/a boys don't run cold air intakes because it's the done thing.

Yeah alright, I'm still convinced that it helps with startup/warmup on a stocker but once you go chasing horsies you need to get rid of it, hence why aftermarket performance manifolds don't accommodate a water jacket (bar a select few).

I understand the intercooling concept and the NA thing, but I really doubt that all the manufacturers that you and I mentioned had missed the mark that much. They were onto something, maybe poor fuel quality of the day needed the additional heat to get the best out of it? but don't modern efi motors have the same thing? Hyundai, Woo, Holden etc.

I guess we need someone who knows their fuels to explain how it all actually happens.

For a stoker yes, for a power-up engine no.

Ultimately cold air is more dense and more will go in. The trade off is cold fuel hitting a cold port wall will coagulate and pool. Air and fuel need to be mixed to burn. High RPM and high flow velocities will pick it up again as fast air is lower pressure and helps revapourise the fuel as the partial pressure it experiences is lower and the turbulence will help pick it up from the wall.

Carbs with cold walled manifolds also have poor transient response. A good thing to read to understand this is reading about X-tau acceleration enritchment on the megasquirt website.

Well, my 1932 Dodge 6 cylinder sedan uses an updraught manifold with a hot spot & my 1933 Coupe used a downdraught manifold with a hot spot.
From memory, so did my FJ Holden & every single carb Datsun I ever saw
This was all well before emmisions regulations came in.

One must ask the famous Julius Sumner Miller question, .... "Why is it so?"
Why did hundreds of auto makers, over a period spanning 80 years or more, include inlet manifold heating when they could have left it off, still [as you claim] provided perfectly normal engine operation, & saved a few sheckles on every engine that they produced.

Would it be the same reason that the thermostat was never eliminated either?

I speculated that the overcooling & the unsatisfactory running of the engine that is the subject of this thread were in fact separate problems.

The overcooling is, I believe, a thermostat problem that it easily fixed, but unsatisfactory stock engine performance, during a wet winter, when operated at low speeds in an urban environment may well be caused by the lack of fuel vaporisation resulting from the removal of the inlet manifold heating function.

I then went on to describe the two main refrigritaion principals that take place at the throttle plate & the resultant loss of fuel vaporisation.
These are
1. Latent heat of evaporation &
2. Temperature drop at the point of pressure drop.

I provided easily demonstrated examples of these principals. [Perspiring is an example of No. 1]

Some symptoms of this can be
1. Reduced power. [Due to the resultant lean mixture as seen by the combustion chamber]
2. Increased fuel consumption. [Due to the higher power settings required to maintain performance]
3. Backfiring through the carb. [again, due to lean mixture]
4. Possible carb icing, resulting in the blockage of some small air passages within the carb. [Fuel jets never block with ice, every mechanic should know that]This results in a rich mixture as a result of the emulsion jet no longer receiving sufficient air, or indeed, any air at all.
A byproduct of this is the reduced atomisation of fuel as it is passed into the airstream from the discharge nozzle because it is not being 'premixed' with air. This in turn makes the problem of overfueling with liquid fuel even worse as the hot spot is no longer hot.

These problems will be greatest in winter, particularly in high humidity conditions such as fog or mist.
They will also be induced at high vacuum settings such as at modest cruise speeds with very low throttle opening.

In warmer temperatures, particularly a hot summer, all of these symptoms may well be non existant as the ambient temperature can easily be high enough to negate the effects completely but right now it's winter in Australia [or soon will be] & it's been wet & bloody cold, just the right conditions for the problems being experienced.

Higher speed engine operation & sub zero temperatures will often overcome some these problems due to higher gas velocity in the inlet manifold, lower vacuum figures & a low humidity due to the sub zero temperatures.

That's my reasoning, but am looking forward to a properly researched counterview instead of a lot of running off at the mouth.

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that statment is perfectly valid but in real terms what efect would it have on an engine at any level of performance? next to 0 i think. and do you mean ports or runners? because about 1min arfter start up your intake ports would be fairly worm and aslong as your not doing 6k everywhere in a cold climate the runners would get plenty hot enough just from engine bay temp. it is realy nither hear nor thair.

dude you make no sense

from what i gather your comparing what dodgeman is saying to heat soak (or something similar) which to me are 2 different subjects

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Actually, old chap, you are right in some respects for reasons you probably haven't thought of yet.

In really cold weather, particularly sub zero, the coolant circulation through the radiator is VERY low & since the coolant that is flowing into the engine is also VERY cold, it has the ability to soak up a LOT of heat before it becomes hot enough to open the thermostat, or to keep it open.
The amount that it opens in an efficient engine can be quite small & the flow is likewise very small.

This means that the coolant in the radiator is exposed to the icy airflow for often a surprisingly long time so if we restrict the airflow through, lets say, half of the core, then we have much less of the core now exchanging heat from the coolant into the air. [The radiator is nothing but a water to air heat exchanger remember]
The result?
Since the radiator is now a less efficient heat exchanger the coolant that reaches the block is a little warmer & absorbes less heat, resulting in an increased coolant flow which puts more hot water into the radiator core which in turn heats the [now restricted] air flowing into the engine bay & this air is being drawn into the carb.

The cylinder head/thermostat will not really see any effective change but the overall temp in the engine bay will be warmer & the engine will thank you for it.
This assumes of course that the engine does not already use a heated air induction system.

Oh yeah, the covering of a portion of the radiator will also reduce the risk of the coolant in the radiator freezing solid in extreme cold, particularly if the coolant is untreated water.

Back in the 1980's & early 90's I was the district Fleet manager for Telecom [as it was known back then] based in Goulburn. My teritory covered a fair bit of south west NSW including Cooma, Berridale, Bombala & the snowfields.
In winter I noted with interest the number of private cars at the various repairers that we used that suffered from this exact condition.

Stock engines with extractors that ran fine in the summer but were absolute dogs in the bitter depths of winter. My own Valiant fleet car was also a victim of this when I had the cracked manifold replaced with extractors in the summer of 1980. [I was the manager, I could get away with this sort of thing]

Refiting a stock manifold rectified the situation overnight & this is how several of the local yokels cars were fixed also. Additionally, I blocked off a portion of the radiator in that Valiant & in my 1200 Ute when in sub zero temperatures & reaped the benefit.

just looking at the manifolds in the tech wiki.. with the ones with the flap inside them and the spring.. how does that operate?

also what bolts to the top of the area with the flap if the carby is sitting right above?

Cheers,
Tom

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