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Discussion Starter #1
Hi
I just found this 2600 intake manifold for a 2600 at friend of mine. Take a look at the pictures..this manifold is identical to a 64 manifold except there is a vacuum connection on the number 6 intake. it looks factory like..but I cannot figure out what this connection could be for..is it for the distributor vacuum ? Has anyone seen this connection before.??
 

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I've never seen that hose nipple before. Given that it is located at the top of the manifold, it should stick out like a sore thumb and should be relatively easy to spot.

As for the purpose, I have no idea what it might have been used for. Ignition advance seems to be a sensible application, but I'm not aware of any distributor ever made for the 2600 that used vacuum advance. So, this (for now) remains a mystery too.

The pictures don't show enough detail to tell for sure whether the hole for this nipple was machined or a cast modification. Can you show us a detail of the base of the nipple behind the carb flange?

One way or the other, one wonders why it was necessary to modify the manifold when a T-piece could have been inserted in the vacuum hose for the brake servo system. If this was done by the factory, there must have been some very rational reasons (both in terms of technical and economic requirements) for adding this nipple.
 

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Discussion Starter #4
Hi Ruedi
The piece looks like an alfa part with the correct slot on the opening and the hole in the manifold was threaded..very strange. i am going to have the hole plugged and use it on my black 2600. i just did not want to use it if it was a rare and valuable occurrence . Could it have been used to create vacuum for a windshield washer system? for a berlin a or a are 2600?
Herve
 

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I just wrote response to a different thread about 2600 OSI with power steering when I noticed what might be a manifold with a similar nipple in a picture I took of Gippo Salvetti's 2600 OSI with chassis number 395012.

There seems to be a small piece of hose with a plug to block it off (or possibly something connected to a black bracket) in the same area your manifold has the nipple. This is a cropped image detail at full resolution of the original image. A close-up would be required to understand whether the hose is plugged or what it is connected to.

So, we know your manifold is rare. Whether it is or ever will be valuable I don't know, but I would not remove the nipple or change the manifold as the manifold will always be an interesting discussion piece in its current form.
 

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Discussion Starter #6
Hi Ruedi
I will find an allen screw to block it off and keep the air nipple handy...
Maybe one day someone will will explain this mystery...
Herve
 

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Discussion Starter #7
unsolved mystery

Hi Ruedi
Since I have not been able to find out what this vacuum port is actually for..and no one has responded with any other example of this anomaly my machine shop advised me to plug it , so no vacuum leak takes place...an other alfa mystery ..
thanks
herve
 

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Hi Herve/Ruedi

I wonder if it might have been used for an inlet manifold vacuum guage - perhaps even attached to the dashboard of whatever car it was originally fitted to.

Herve - you may recall giving me some advice on the inner headlining material for my 2600 Spider back in March. I bought a cashmere/silk fabric offcut on ebay and the hood was eventually fitted two weeks ago - the day before I went away on holiday. The hood requires a little stretching/settling to get all of the tenax fasteners to hold but when it eventually stops raining here and the hood has settled I'll take some pictures and add a new post. My thanks again for your advice.

best wishes

Brian
 

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Hi all,
I have fitted three 40mm Dellortos to my 2600 (ex 2000 GTV still with standard jetting) but while every thing runs perfectly in the garage, the moment I apply throttle when on the road, it all bogs down. I have received mixed messages on the cause which vary from the need to de-Siamese the inlet manifold through to needing to double all jet sizes. I am seeking more info before I consider doing anything that is irreversible.
I have read about Weber Manifolds but have no other information.
Can anyone who has done such work already, offer me some comment.

Thanks

Paul Crosbie, Ballarat Australia
'66 2600 Sprint
'80 Spider
 

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Hi

Yes I have been watching the email correspondence on alfa2600 with interest.

I'll let you know what I know , although it may be BS.

I have tried as you 40mm dellortos jetted for an alfa 1750 x3 on a std siamised manifold with the same results as your state.

Same units on a de-siamised manifold run well ( I am lucky to own an original Weber manifold) - easy starting and good progression , but I currently have a lack of top end power. But this is more likely to be the tired state of my engine with low compression on two cylinders.

Weber 45 that I have show the same problems on a siamised manifold and on a de-siamised manifold , I am currently following the path of adding one further progression hole.

I have heard statements that Webers /dellortos can be run on the siamised manifold but no-one yet has come up with the numbers jet sizes etc to back this up.

To be honest my car ran best on Solexes set up as std

good luck

Ian
 

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I have the luck to navigate with my friend in a couple of different tarmac and dirt cars. Ian's (Merlin's) comment echos my friends standard reply which is the manufactures has spent millions getting their designs right so the best thing to do is keep it standard. Of course like the rest of us, he also does the opposite.

Thank you all for your replies

Paul Crosbie, Ballarat Australia
 

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Regarding the additional vacuum outlet on the 2600 inlet manifold,my original 2600 workshop manual refers to the distributor on the sedan has a vacuum advance. Perhaps this is its use although why not do the take off at the front end of the manifold. Need to check with someone who has an original Berlina. The same manual refers to a dual point distributor on the Sprint and Spider but the two Sprints I have had ('62 and '66) had single point units.

Paul Crosbie, Ballarat Australia.
 

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Berlinas had a completely different manifold with Solex C 32 PAIA downdraft carbs. The vacuum advance was connected to these carbs, not the manifold.

Distributors were either dual-point Marelli or single-point Bosch units. I have not yet found any documentation that would indicate whether such equipment selection was based on destination (country to which the cars were delivered) or relatively random based on what they had available.
 

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A CRY FOR HELP.
A lack of sufficient information has prompted me to forget getting three 40mm Dellortos to work on my 2600. I have gone back to the Solexes and now have to solve the problem that prompted my attempted change in the first place.

My nice new engine will not rev over 4500 rpm under load and I can't fimd out why so I am beeging for any ideas. It pulls nicely to 4000 then stagnates. My suspician is that its suffering fuel starvation and perhaps even the second throats just not opening. (Is there an easy way to chack?
I have done the following:
rebuilt the carks with new kits including the vacuum chambers to actuate the second throat. I have replaced the fuel pump with various alternatives to ensure I have both the pressure and volume required. I have tried it without an air cleaner in case that was the cause. Obviously I checked ignition timing and spark advance and they are both OK.

Some days I wish I had just bought a Nissan or a Honda.

Any ideas would be greatly appreciated.

Paul Crosbie, Ballarat Australia
 

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I agree that I would look at the ignition first. As RPMs increase, the charge time for the coil is reduced, which leads to a weaker spark and possibly to incomplete combustion (i.e. less power). Check the rotor first, and make sure it's a correct one (as ignition advance shifts the position of the contacts in relation to the contacts on the distributor cap. Then, check contacts and capacitor, then coil and cables.

If it's not related to the ignition, I'd next check if valve timing (camshaft alignment) is in spec (including if there's slack in the driving chain).

Last but not least, check the exhaust system for flow problems (back pressure) by removing the mufflers for a quick drive.
 

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4,000 rpm limit

Strangely I have a similar problem with my 2600

Running on Dellortos DHLA 40 jetted as for a 1750 GTV with a Weber manifold The car starts fine and runs up to around 4,000 rpm and then produces no more power. I am not going go try and fix it until my engine is rebuilt, as I have two cylinders with less than 60 psi pressure.

If I fit Webers instead of Dellortos , I have the familiar flat spot on acceleration
but no limit to revs . So I would suspect the carbs

The Solexes should be fairly easy to test . The balance weights for the secondary chokes should be free to move. If you pull the up to open the butterflies on the second choke they should easily close when you let go .

To test function should again be easy if noisy - get someone to accelerate the engine and see if the secondaries open at around 3,000 rpm - if not they are sticking and this as you suspect is the reason for no power above 4,000 rpm

cheers

Ian
 
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