Whoh,

Seeing that theres so much to do and so little time, to pep up a bit of power to the Datto, without taking of the head, conversions etc, I think that I rather put up with sluggishness, and rather then put on a complete 2nd hand motor and g\box from a newer model a14 ute.

I'm sure this would be an easier option and cheaper as well.

Thanks alot guys, I'm glad that I didnt purchase these carbis and mainfold, without consulting with you all.
Cause at first I thaught that it'll be a perfect, hassle free solution, well I was wrong..



PEACE OUT

Quote:
The original post in this thread refered to the original GX carb setup, & i have stayed with that all along. I know that some people have installed SU's on their "A" series engines, but i am sticking with the Hitachi's in my posts.

Ddgonzal
There wasn't ever a factory twin Hitachi, or SU setup for the 1000 as far as i can tell. I lament greatly the fact that i passed up on a twin SU maniflod for the 1000, by Aussie maker "Lynx," at a swap meet about 20 years ago. They were asking $35, with a tatty pair of carbs.

These manifolds will also fit the later round port heads, but were actually made for the 1000 as they have no provision for a PCV valve, & the 1000 had a draught tube crankcase ventilation system.
Surely "someone" made a 1200 version

One of our members has one of these 1000 manifolds & it should make a 1000 engine run quite nicely with a well tuned pair of suitably small carbs.

Quote: The original GX carbs are Hitachi's, while the carbs that are the product of "Skinner Union" are SU's
Both of these two carbs are of the "variable venturi" type but there are no SU Hitachi's, & no Hitachi SU's just Hitachi, or SU carbs
The Hitachi carbs on the GX are, as i wrote, semi sidedraught, variable venturi types, & those on other 1200's are of the downdraught type.
Adding the letters "SU" when describing GX carbs just confuses the issue.

confusing ... as some have fitted SUs to a 1200 using euro or custom manifold ... so be careful what you write. i would expect less takeoff power he only carb and manifold is changed. D-man, are not the 1000 dual setups round?

Dodgeman

I know they are Hitachi SU's.
This you have mentioned to me a couple of times. Even in the mails I send you in the past asking for some advice.
I am just too lazy to type out HITACHI SU's.
It is quicker for me to type only SU.
If I mislead someone in this I am sorry.
About the A15 or A14 cylinder head story.
I think it was discussed before I joined this site.

Tommy.
Basically check everything that moves inside the carbs to see if they have grinding marks or a play on them.
Check how clean they are on the inside.
If they are clean, the guy probably used a aircleaner.Witch is good.
What I did in connection with the butterfly wear, I held the carb up into the sunlight with the butterfly in the closed possition.
There must not come any sunlight in around the edges of the butterflies and the bushes that opens and closes the butterfly.
This is where mine had wear that I bought as spares from someone.Small amount of sunlight was visible around the bushes.
This will cause them to idle too high as too much air and fuel will be coming in.

Dodgeman.
I leave the corrections to you if I made any mistakes on this.

how do i check the butterflies and all that on SU's as i am buyin a pair from a bloke and am havin a look at them on Saturday. They are apparently in good nick. How much should i expect 2 pay. There on a a15 manifold 2!

As has been mentioned on this site, many many times, the A14/15 heads have the oval ports & the correct bolt pattern.
There are really only two manifold bolt patterns. One for round ports, & the other for oval ports.

As has also been mentioned in this thread, they are NOT SU's,... they are Hitachi's.
If the throttle shafts become worn, any decent carb specialist worth the name can drill the carb body & fit bushes. They should also be able to replace the shaft, thereby restoring the carb to "as new" condition.

The A14/15 heads can be used on the 1200 block, but
A. Check the combustion chamber volume of the replacement head before using as a larger chamber means lower compression, &..

B. Modify the head so that the rockers get oil. This may mean grinding a small groove in the gasket face from the place where oil comes out of the block, across th the nearest head bolt hole.
Machining a groove would be best.

Dodgeman.
Yes, you are right the manifold will not fit onto his head.
But I saw yesterday at the suspention place where my suspention rubbers were replaced a A14 utility that they fitted a SU intake manifold and two SU's.
It is maybe possible it is a oval A14 head with the correct bolt pattern.
Do you know if the A15 cylinder head with oval ports have the correct bolt pattern for the SU intake manifold?

Reeves.
I think your best option would be for a single 40 sidedraft weber and extractors.
Your problem will be that you will have to fabricate your own intake manifold.
If my SU's gets worn out so that they are not usable anymore, I am going to fit a single sidedraft weber.

1200GXman
If he has the standard head, then the GX manifold will not fit, & even if it did fit the head, the manifolds oval ports are bigger than the standard round ones, so it would be better to get an aftermarket twin SU manifold, & see if it is possible to get the whole carb setup from a Mini cooper, or MG sports car.
This would be a great time to switch to a set of extractors/ headers too.

Once the carbs are correctly tuned, the fuel consumption will be totally controlled by the drivers right foot.

Always remember this.
Power is made by burning fuel. You want more power, you burn more fuel. It really is that simple.

I managed to get over 50mpg from my engine one day when i drove strictly for economy, yet it delivered all the performance that i needed when i asked it to, & mine was a slightly improved 1200GX engine. [big bore] Thats better than 17.6 killer-metres per liter of fuel.

On a midnight run from Albury, in NSW, to Bendigo in Victoria one night, i averaged just over 71mph [114kph] for the 250 mile [400k] trip & averaged just over 42 mpg [14.8 k/l]
Is that good enough economy at cruising speed?

Thats what i loved about my car, good performance, or great economy, it was all up to me.

Oops.
Dodgeman are right.

The GX engine did come with all those extra stuff as mentioned.
But Dodgeman I would like to know something.
Will he not get a bit better performance with the Su's and still have good fuel consumption?

A Nissan mechanic friend of mine said that SU's give better torque than the standard carb that the deluxe came out with.
The head will also help with torque because it gives better compresion and as far as I know higher Comp gives more torque.
I am trying to help Reeves with a cheap power upgrade without opening the engine.

The Datsun 1200GX did NOT get it's higher performance from the twin Hitachi's

To assume that a single thing will make all the diference is pure folly.
Those really clever engineers at Datsun built a whole GX engine instead of just adding carbs to an existing one

The GX engine had more compression from it's flat top pistons
It had the twin carbs as already noted.
It had a well designed free flowing dual outlet exhaust manifold.
It had a better cam profile that was tailored to the engines new performance level
It had double valve springs to cope with the higher revs that it was capable of
It had a whole new cylinder head with larger, oval shaped inlet ports. This head also had a diferent bolt pattern to bolt the manifold on & the manifold will not fit the standard 1200 head.
Even the fuel pump was changed to provide slightly more fuel pressure.
The water inlet pipe on the block is diferent to accomodate the water hose from the inlet manifold.

Other than that, they are pretty much the same. From this it's obvious that the carbs are just a part of a well balanced package of components, & thats why the GX is so good.

You may be able to duplicate the GX pistons if Datsun 1000's were sold in SA. The 1000 used a flat top piston with a longish skirt. When the 1200 came along, with it's longer stroke, they shortened the skirt to prevent it hitting the crank, & they made a dish in the crown to maintain the compression ratio.

In Australia, Repco decided that they could cut costs by making pistons for both engines by using the shorter skirt 1200 blank They machined a flat top for the 1000, & a dish for 1200's
If one uses the "replacement" 1000 piston, you get a flat top piston for use in your 1200. If you have replacement piston makers in SA, then check to see if such a thing is available.

This is what i used in my wife's green 1000 two door. The pistons for both models of engine were the same price, so i got a modest boost in compression for FREE

By all means, get the GX inlet system, but get the rest of it as well.