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[Spooty22]

Hi,
I have just purchased a twin carb (95hp) motor for my 1980 sud Ti. The motor was taken from an '85 33.
Having never seen a twin carb motor up close, i am wondering whether the Marelli distributor is supposed to have vacuum advance?? Mine doesn't - only mechanical advance. The Bosch distributor on my single carb sud had a vacuum unit.

Also, in each inlet manifold, there is a sensor. One has one connector, while the other has two.
What are these for? An idle cut off solenoid for each manifold?

Any help would be much appreciated!!
Thankyou
Spooty22

[Chris Notsis]

The Marelli in fact DOES have vac advance, as well as the mechanical set-up. Has the vac diaphragm been removed?

Sensors? THe idle compensator solenoid ( 1 only) sits inboard of the right hand carb. THese quite commonly fail and and the car tends to not notice its absence! As for the sensors you mention, inserted into each intake manifold: no idea. Could this be a local market inclusion? Are you sure this is where they are? If such sensors are in the intake tubes, then they would need to be air volume sensors, but the 33s of that period never had such sophisticated technology! Behind the right carbs is a sensor for oil pressure, but it is not in the intake tubes.
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Chris Notsis

[Spooty22]

Hi Chris, thanks for your help

The motor is actually an Australian model!
The idle compensator must be the strange device i see integrated into the throttle cross-shaft inboard of the right carb. It seems to form a circuit whenever the car returns to idle. Is this it?

The vac advance may have been removed from the dizzy, i'm not sure, but there doesn't appear to be any provision for one on the dizzy body - no holes, nothing. Only two small holes in the side of the distributor cap.

As for the sensors, when i say inlet manifolds i am talking of the very small air pipes underneath each carb, on the cylinder heads. In the side of each of these, (underneath the carbs) is a sensor of some sort, complete with electrical spade connectors.

Bit confusing i guess.

[Chris Notsis]

The fast idle compensator solenoid creates an over-run state when de-throttling. It holds the revs at about 2,000 for a couple of seconds. Not an issue at this stage of the game if it doesn't work. Corrosion gets into the shaft of the activated pin and the solenoid can seize. THey're too expensive to replace.

My guess is that someone has removed the diaphragm vac unit from the dizzy. Can't see why, unless the diaphragm itself leaked, or the someone thought it was reducing performance or something stupid. Either add one or relpace the dizzy. Without it, the advance is then dependent on the governor weights inside the unit - not ideal, since they activate only at about 4,300 rpm. In the meantime, the engine can ping. The vac advance makes the advance transitions smoother, allowing the ignition to better cope with load and timing changes based on this.

The terminals you mention - the one on the outer right hand side, near the throat for Cyl 3, is related to the fast idle compensator (and tachymetric device) and has a voltage when the throttle opens. You can usually see a small spark when the throttle opens. THe little wire terminating here can break. It also needs to be connected because the idle can rise if not. As for the sensors on the inboard side of the carbs - these are coolant related and need to be connected. They can affect temp readings and timing if not connected / functioning. They are not prone to failure; usually the wiring can cause problems.
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Chris Notsis

[spooty22]

Thanks Chris,

i had a closer look at the sensors. (removed them) One is a sensor for the water temp gauge (it has 'jaeger' written on it, just like my sud motor) while the other one is also coolant related and appears to be a switch. Not sure what it is for - most likely only important on the 33 as the sud never had anything like this. I will leave it disconnected on the sud. I am thinking i will also leave the idle compensator completely disconnected as i have no idea how to integrate it into the sud wiring loom.

Also - my sud has 3 lines coming from the fuel tank - fuel delivery, fuel return, and something which i assume is from a charcoal canister of sorts. I have no idea what to do with this third line as there is nowhere which wants to accomodate it on my new motor. (on the old single carb weber DATRA it plugged into the carb)

In regards to the dizzy, i am going to replace the Marelli with the Bosch JGFUD-4 electronic unit from my single carb sud motor. The Bosch has vac. advance. According to the Haynes manual, all late model suds (including the twin carb) had identical ignition timing. But i am not sure. Surely the single carb and twin carb had different advance curves???

I will try it out and see how it goes.

[Chris Notsis]

THe extra thermoswitches / sensors on the 33 are refinements of the Sud setups, in that by 1985, Alfa had begun to catch up to the idea that coolant temp, engine oil temp, air temp and engine response had something to do with each other! That and more stringent emissions laws in Europe, compelled a closer relationship been made by these systems in an effort to reduce emissions caused by a poor inter-relationship between timing, ignition output and fuel combustion being influenced by temperature.

As for moving to a Bosch from the Sud - that should be fine, since the late 1.5 Suds and the 85 33 shared similar tiimng responses. One appraoch is to have the thing dyno-tested, or use plain suck-it-and-see! As long as the engine operates in the temp range for which it was engineered, then timing issues won't arise. You could even advance timing by up to another 2 degrees.

Cheers

Chris.
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Chris Notsis

[Vecchio Alfisti]

I realise that this thread is nearly a year old but I have just come across a similar situation. Last week I acquired a 1985 1.5 litre Green cloverleaf in Melbourne, engine type 30182 twin carb and would you believe, the distributor has NO vacuum advance. and never had. As I have the books for the car from new plus a wad of receipts I have looked for replacement distributor and it hasn't happened. Nor is there any provision in terms of tapping points on the carby or manifolds for a vacuum connection. I am wondering what sort of engine I have got and what were people thinking when they produced it in the marketplace. Should I look for another distrubtor?

All ideas welcomed

The car will not be going anyplace for a little while because I think that the timing on one bank is out by one tooth. That is another story.
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Alfa 33 1.7 QF I think maybe now I m not so sure

[Chris Notsis]

Hi.

The models that appear to have a vac advance unit were the Series 1 33s. The 1985 Greens had lost the unit because better calibration and control by the ignition module, and that the mechanical advance created by the governor springs AND the rotor button compensated for the absence of a vac advance. I have been without my 33 that I had all but forgotten some details, but have checked my own files and records on the thing. As you have found, timing can be thrown considerably by one-tooth-out settings. The setting of the timing (both sides) is absolutely critical in the Series 2s and beyond. The Series 1s had a little more tolerance. Vac advance can allow a larger margin of error. So, in your case, the sooner you set the belts right, the better.

No, don't bother with a new dizzy. Consider replacing the cap and rotor before adjusting the belts. The rotor is a critical item in the Series 2s

Hope this helps.

Chris.
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Chris Notsis

[Vecchio Alfisti]

Thank you Chris. That is really helpful as I haven't found any reference to it anywhere else.

John
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Alfa 33 1.7 QF I think maybe now I m not so sure