Yes, I agree that the SU's are a better choice if you are going to set them up properly (professionally rebuilt and dyno tuned). I've run just all the popular types of induction on my A15, stock Hitachi, Weber 32/36 DGV, GX dual SU's, and 40mm Dellorto's. I think the SU's were the best for all around performance and reliability. They performed a lot better than the 32/36 Weber and got the same gas mileage (~35-38 miles per gallon), and while the Dellorto's definitely give the most power, the SU's weren't far behind and the gas mileage is worse with Dellorto's and it's constant upkeep. The SU's once set right don't require a lot of attention at all. I cheated mine and instead of going with a different needle/spring (not much SU support in the US) to set my mixture richer, I just thickened the damper oil and it worked great! They really are a simple carb when you learn them too.

I'm still anxious to see how a properly tuned EFI setup would go on the A series though in comparison to the rest. My poor A15 that I've been running for about 8 years now has never been truly "tuned" with a dyno or wideband O2. I bet there's still a lot of power to be had out of it. Maybe when I return to the US I'll give it a shot.

-Andy

Hi

Dodgeman & L18_B110 know their stuff.

I just want add a couple of things,being a Carby guy.

The biggest problem with SU carbs besides the excessive wear they are prone to in the throttle shafts & bushes which happens because they are both made out of brass,(this can be fixed permanantly by installing teflon bushes & new shafts) is LINKAGE SETUPS thats where the myth comes from.

The "coming out of tune thing" is because the majority of people out there using multiple SU's have absloutly disgusting linkage setups. You can NOT tune and balance any multiple carb setup which has crap linkages.

Always use rosejoints, high quality thottle arms and correct tension return springs on each carb(SU). Theres only two main jet sizes for SU's,90thou & 100 thou,depending on the model. There are many metering pins. Once you get the pins right and good linkage system SU's are excellent.

Theres a lot less stuffing around with a 32/36 weber, and they are a good carb so dont go chucking your DGV just yet.They are very low maintanence once jetted correctly.

As for the Hitachi's (SU type) definatly dont throw them out. They are original equipment, and in my opinion work better than a lot of the SU models. The kits are getting very expensive for them.

Anyway, hope that shed some light.

P.S LINKAGES!!!!!!!!!!!

Quote:
Huzzah. I've been saying this for years, except that i always refered specificly to the Hitachi's as i have many driving years of experience with mine. The only genuine SU's i ever actually used were on my '52 Morris Minor [i didn't know any better, OK]

Nobody really wants to know about this, as a pair of these SU / Hitachi's don't look as sexy, or sound as horny, or make as much top end power as Webbers, but on a car that you actually drive,... a lot, they are a very good choice.
Low maintainance, modest initial cost, & good all round performance are attributes that are hard to beat in a driver. Thats why the factory used them.
If you are going to use the Genuine British SU's on an A12 or A14, then I guess that a pair from a Mini or Sprite / Midget might be a good start.

Sarav1200
You got the linkage problem absolutely right. This is probably one of the reasons that the stock GX setup is so good. The factory linkage is well designed & the carbs stay in phase. I think we have all seen some linkages that could have stood a little improvement,... well, OK, a lot of improvement.

lets not get too carried away, they do have some limitations in performance engines.

when you use even a moderate street cam, idle quality and mixtures are quite poor due to the lack of (or fluctuations of) idle vacuum. once off idle though everything is OK. I think the lumpy idle was a major factor in the breaking engine mount problem I had.

The exposed fuel bowls are also very sensitive to heat soak, and fuel is prone to boiling or vaporising during extended idle periods in warm weather. This is more of a problem if you have extractors - which most of us would. Good heat sheilding and thermal wrapping the fuel bowls overcomes the problem pretty easily and cheaply.

On the up side, they are great for fuel economy, especially on the highway. And have very good low end transitional response.

I just wondering which part of the carb is the "damper"? I understand you put some oil on it!

On the top of each carb is a large, wavy edged, serated, or knurled knob. If you unscrew this by hand, you will be able to pull it out. It has a rod on the underside with a brass collar. This thing is a crude form of shock absorber & stops the internal piston, which is suspended on air pressure on one side, & partial vacuum on the other side, from bouncing up & down when driving. It also regulates the speed at which the piston rises when you hit the "power pedal".

Some blokes reckon it's the hot setup to leave it out, or at least run no oil at all. This is a total falsehood. Oils of difering viscosity are used to fine tune the opening rate & auto trans oil is often the recomended oil, but i used engine oil. This is a heavier viscosity & slowed the opening rate. The trade off is that my maximum possible acceleration was less than optimal, but i got great cruising characteristics & fabulous mileage.

L18_B110
The cam in my engine is described as a "Light Sports Grind" but no actual specs were forthcoming when i bought it from Repco in about 1983. I pushed the idle up to about 900 or 950 rpm & low speed characteristics were "quite acceptable" Like everything else, it's all a matter of balance, & i built my engine for my particular type of driving. It worked a treat for me & my particular application..

By jingoes

I didnt realise there ws soo much to it..
Well the throttle inkkage looks ok to me, but im not an expert on them. I am thinking that I will get them done by the pros and tuned by them as well.
I will be doing a pics session this break (next week) and i will get them up so that you guys can ave a captn cook...

Lately my 1200 Datsun pickup 1993 has been hestitating and slightly jerking when I accelerate.
It happens both when the car is cold and warm and in the beginning of the acceleration.
Even when I change gear and start to accelerate!
There is a serious lack of power and it is so annoying... sometimes the engine stalls.

I recently changed my plugs, oil, and air/fule filters, battery etc...
Imagine, joining a High-Way and want to accelerate before the approaching cars arrive, there it goes duf duf, hesitate!

I have read many articles on this problem and they say the culprits are:

1). A light stumble only when accelerating from idle could possibly be caused by the idle adjusting screw,
being turned in too far. or

2). The accelerator pump circuit. http://www.theautoist.com/weber_carb.htm or

3). Acceleration hesitation is caused by Vacuum leaks.

Point (1) cannot be my problem, because I have adjusted idling and it's good.

Point (2) might not be the problem. But it is a potential. When I opened up the carb last week-end I made sure the Accelerator Jet squirts a fine spray into the throttle.

I have cleaned my carb many times making sure there is no blockage. One time I put bigger jets (two times bigger that what are there).
The problem disappeared but fuel consumption doubled, and the exhaust pipe turned black. The link above discourages
people from putting bigger jets to cure hesitation.

Could it be Vacuum leak? I suspect this because I realised that the Primary Throttle Shaft has too much free play.
On the contrary, the Secondary Shaft is tighter. Can this be re-built?

What do you guys suggest? I am feeling so bad about this problem.
I do not want to buy another carb if this can be solved.

It is a Hitachi carburator.

AlphDoti
If your engine is stock, then do not change the jet sizes away from stock sizes as these are a proven combination.
The primary throttle shaft is the one that will wear the most as it is in use ALL the time, while the secondary is used only occasionally.
Contrary to what some may say, the original Hitachi carb is a good, proven design carb, & it is ideal when used in stock applications.

If you have a vacuum leak, it would mess with the idle more than anything else. If this leak was at the "manifold to head" gasket, the leak would affect one cylinder more than the others & may even show up as a missfire at idle. Vacuum leaks often whistle if they are in the carb area. Check the tightness of all manifold & carb bolts.

A worn throttle shaft may well have the effect that you describe. So will a faulty accelerator pump, which you have checked. If the primary shaft is badly worn, you have four options.
Live with it
Fit a good used base or carb.
Have the base reconditioned with new bushings & shaft.
Fit a new base assembly.
The last three are my recomendations.

A blocked intermediate circuit will also give you "off idle" problems. This can be checked by simply screwing the idle speed screw progressively open.[not the idle mixture screw] What happens is that as the throttle slowly opens, & the rpm's rise, the idle circuit can no longer supply enough fuel, & the airflow is not yet enough to start to draw fuel from the main metering circuit.

There is a small orifice, just up from the idle port, just above the throttle plate when it is closed, & it starts to feed fuel once the throttle is open a little bit. This fills in the gap between idle speed fuel needs, & the time when the airflow is enough to draw fuel from the main metering circuit. If this intermediate circuit is blocked, the engine will lean out as you screw the idle speed adjustment in. & the engine will stumble. It may even stall. The accelerator pump will have no role to play when the throttle is opened as slowly as this, so it will not mask the symptoms.

Make sure that the engine is properly tuned, & all the idle settings are right on the money BEFORE doing this simple test. Also make absolutely sure that the fuel LEVEL is correct in the float bowl by inspecting the little window in the carb while the engine is idling. It should be in the middle of the window, level with the little dot marked in the glass. If it is not correct, then fix it before proceding further.

If this intermediate circuit is the problem, then pull the carb down & blow compressed air in the reverse direction through the port to clear it.

I hope this is of some help.
Chris

Hi AlphDoti

Dodgeman pretty much covered it,I just want to add 2 things:

1- Make sure that you get instananious pump squirt opening the throttle SLOWLY,you should be able to see fuel almost dribbling out the pump Jet.

2-Make sure you havnt got manifold vacum at your vacuum advance on the distributor,
( It causes a similar symptom to what your describing)