Any Dellorto experts?? 40 DRLA's?

[Paul Reveres Ghia]

I bought these carbs on ebay as they were sold as being "perfect for vw 1600's" - I am a total novice when it comes to these things but really wanted to run dual carbs on my motor so they seemed like a good idea-











I believe them to be from an Alfa- Any of you guy's tell me what is necessary to convert them for an ACVW?

Cheers

Seth

[deanosvws]

hi there, you need to take the cold start off (last photo) as it is not needed. on the top of the carbs you have two divets that need drilling and tapping to take two extra studs for air filter bases. depending on which linkage you use will determin what arms you need to fit to the spindles. cb hex bar is one of the best linkage kits for these carbs. also the jetting and venturi's need to be checked to see what you have and what you need. the carb on the left needs the vacuum pipe sealing of (top right).  cheers dean

[Paul Reveres Ghia]

hi there, you need to take the cold start off (last photo) as it is not needed. on the top of the carbs you have two divets that need drilling and tapping to take two extra studs for air filter bases. depending on which linkage you use will determin what arms you need to fit to the spindles. cb hex bar is one of the best linkage kits for these carbs. also the jetting and venturi's need to be checked to see what you have and what you need. the carb on the left needs the vacuum pipe sealing of (top right).  cheers dean

Thanks Dean,



Is this the Vacumn pipe? What's the best method to block them off?? I was thinking of getting the CB linkage- Guess I will now- (Unless the new CSP cross bar linkage looks as good or better?)

With the cold start- Do I just remove it? Nothing needs blocking off or changing??

Finally, How do I route the fuel lines? Why are there so many unions for them?

Many thanks for your help.

Seth

[Bruce]

Is this the Vacumn pipe? What's the best method to block them off??

The best way to plug that vacuum tube is to connect it to your vacuum advance distributor.

[Neil Davies]

When I ran 36 Dells on my 1600 I had the fuel pipe coming into one carb, then another pipe joining that carb to the opposite one, finally blocking off the smaller fitting on the union. You could run a return to tank I suppose, but I just blocked it off with a small piece of pipe with a plug in the end. The nice thing about doing it that way is that you can use a solid fuel line P-clipped across the back of the fan shroud (I used copper) and there is very little chance of there being any leaks.

[deanosvws]

 the vacuum pipe can be conected to the dissy as bruce says but if you are running a 009 for example it needs to be blocked off at the carb. you could use either a bit of rubber with a bolt in the end or epoxy the end, as long as the air is not being sucked in. the cold start just needs to be taken off.
cheers dean

[Paul Reveres Ghia]

Excellent- Thanks for your replies guy's- I am indeed running an 009 so will block off the vacumn pipe- I'm going to have a try at removing the cold start now- 

[Fasterbrit]

Is this the Vacumn pipe? What's the best method to block them off??

The best way to plug that vacuum tube is to connect it to your vacuum advance distributor.

The single signal from one barrel to the distributor advance mech will result in a very erratic advance. It will literally 'bounce' up and down non-stop as much as 20 degrees! On a stock setup the signal is from all four cylinders and is nicely balanced. These even pulses make a for a smooth advance.

[Rasser]

Make sure the venturis are sized properly, this will the engine MUCH easier to drive.   
Stock 1600?   -  I would choose 26 or 28mm for this kind of engine.

Also you should check what the numbers are on the emulsion tubes. I can´t remember what the best tubes are for acvw, but do a search, it is mentioned on this forum somewhere, if I remember correct.

[Bruce]

Also you should check what the numbers are on the emulsion tubes. I can´t remember what the best tubes are for acvw,

9164.2

[Bruce]

The single signal from one barrel to the distributor advance mech will result in a very erratic advance. It will literally 'bounce' up and down non-stop as much as 20 degrees!

How did you observe this?

[Corally]

Hi there. Im curently running 40 mm dells on my stock 1600 with a 009 bosch distributor.

118 main jets
55 idle jets
28 mm venturi's

runs like a dream. Vacuum blocked of by soddering the end shut. In my setup i use a hexbar from CB but i'm not really pleased with it. It's got a lot of play in the ends of the hex bar. Think you're better of with a bell crank from CSP.

i'll follow the topic!

[Fasterbrit]

The single signal from one barrel to the distributor advance mech will result in a very erratic advance. It will literally 'bounce' up and down non-stop as much as 20 degrees!

How did you observe this?

With a strobe timing light.

[Torben Alstrup]

In my setup i use a hexbar from CB but i'm not really pleased with it. It's got a lot of play in the ends of the hex bar. Think you're better of with a bell crank from CSP.

NO! The CSP push pull is definitely not worth the swop IMO.  The new CSP hex bar system is very nice though, if you have straight manifolds. Take the Cb hex bar and the pivot joints and send them to me. (35 € labor) I will do a slight modification on them and you will be in business for the next 40,000 miles.

30 mm venturies work fine with a fresh stock cammed 1600. I only use 28´s when the customer wants max torque below 2500 rpm.
T

[Bruce]

The single signal from one barrel to the distributor advance mech will result in a very erratic advance. It will literally 'bounce' up and down non-stop as much as 20 degrees!

How did you observe this?

With a strobe timing light.

Sounds like you had a distributor problem.  Or maybe your cam didn't provide enough vacuum.

When I looked at the timing of my distributor using only the one tube from the left carb, the timing was dead steady.  Given the number of carb pairs with only one tube installed on Alfas and Fiats, I don't think the single signal is a problem.

[Fasterbrit]

The single signal from one barrel to the distributor advance mech will result in a very erratic advance. It will literally 'bounce' up and down non-stop as much as 20 degrees!

How did you observe this?

With a strobe timing light.

Sounds like you had a distributor problem.  Or maybe your cam didn't provide enough vacuum.

When I looked at the timing of my distributor using only the one tube from the left carb, the timing was dead steady.  Given the number of carb pairs with only one tube installed on Alfas and Fiats, I don't think the single signal is a problem.

As a test on the same engine/carb combo I then linked the four carburettor sync balance ports to one pipe and attached this to the distributor advance port. The erratic advance pulsing vanished and the timing held steady. If you think about the logic of the single barrel signal from one cylinder, then it will only be pulling vacuum when that given cylinder is on its induction stroke. When the other three cylinders are doing their induction stroke there is no signal to the distributor. Therefore for 75% of the time a single port is not going to be pulling enough vacuum (if at all) to cope with a VW distributor. This is why the timing 'pulses' wildly in VW mode. Whether Alfa had a much more sensitive advance mech on their distributors is a question I can't answer as I have no experience there.

[Torben Alstrup]

You need a pulse dampener to run the vacum from only one port. (A simple moped fuel filter will do the job.) I´m not sure how the vacum reacts at higher rpms when taken through the sync ports. My first reaction would be no go, as it will only work just off idle. But I will have to look at a carburettor to make sure.
T

[Bruce]

... I then linked the four carburettor sync balance ports to one pipe and attached this to the distributor advance port.

That's manifold vacuum, not ported vacuum.  I don't think a test involving that irrelevant source of vacuum is all that useful.  Sure, 4 will have less fluctuation than 1, but you can't use manifold vacuum. 
I don't deny that hooking up more than one should be better, but when you buy a matched pair, you only get one port.  The biggest influence on how much vacuum you can get is the cam.  A smaller cam will give a lot stronger vacuum signal.
I just realized that I have a spare orphan 40DRLA.  I wonder if it's got a vacuum port.......

[Torben Alstrup]

Yeah, that´s what I thought. But couldnt picture the holes on the inside in my head at the time.
T

[Fasterbrit]

... I then linked the four carburettor sync balance ports to one pipe and attached this to the distributor advance port.

That's manifold vacuum, not ported vacuum.  I don't think a test involving that irrelevant source of vacuum is all that useful.  Sure, 4 will have less fluctuation than 1, but you can't use manifold vacuum. 

Hi Bruce. Just had a good look at a DRLA and when the throttle plate is fully shut, the original vacuum signal intended for the distributor is half exposed to manifold vacuum i.e. the throttle plate does not fully cover up the distributor take off port. Therefore, the port is exposed to manifold vacuum, just like the 4 balance ports. I am a little fuzzy on what you describe as an irrelevant vacuum source. Is there any chance you could explain this a little so that I can get my head round this issue. Thanks in advance, matt

[JamieL]

AFAIK - Alfa fitted an Anti-Pulse Valve in between the carb and distributor on some such DRLA + vac advance engines to avoid this single cylinder vacuum problem.

The only time I have lifted DRLA's off an Alfa from the scrapyard I also managed to get the APV, but haven't had a chance to test this on a motor yet...

[viNce]

Take the Cb hex bar and the pivot joints and send them to me. (35 € labor) I will do a slight modification on them and you will be in business for the next 40,000 miles.

Something like this? 





viNce