Author Topic: DCD carburetor linkages  (Read 2434 times)

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Offline zippyfiat

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DCD carburetor linkages
« on: November 23, 2007, 06:32:27 PM »
Hi all, I am wondering if anyone can clarify what is the correct arrangement for the linkage for a DCD carburetor on an Abarth?  The first two photos are a later type DCD carb I have sitting on the head along with a 600 rocker cover (aftermarket alloy one).  The third photo is an earlier DCD3 carb.  Note how on the DCD3 carb, that the linkage arm on the carb points down, but on the later DCD carb, the linkage arm points up.

It seems that by looking at various photos I have seen, the linkage on the Abarth cars points down.  I also understand that a DCD7 carb was "standard" fitment?  Using an earlier DCD carb (DCD3, DCD7) the linkage rod from the rocker cover would push to the passenger side of the car. 

However, with a later DCD carb, the linkage rod would pull to the driver's side of the car.  Using the later DCD carb works easily with the linkage arm on top of a  standard 600 rocker cover, as the stock arrangement pulls the linkage rod.

How is the linkage on top of the rocker cover set up on an Abarth so the the linkage rod pushes towards the passenger side?  Or should I just rotate the linkage arm on the carb and be done with it?

Also, can anyone tell me if it matters much if I use a DCD3 or DCD7 carb?  Were they both made as a 28/36, or is one a 28/36 and the other a 36/36?  Can I get away with a 36/36 on the street (with 1050cc)?

Thanks,
Gil


Offline grant gauld

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Re: DCD carburetor linkages
« Reply #1 on: November 23, 2007, 08:16:20 PM »
For an example of a DCD 7 36/36 on a 1050cc motor (NOT an A112),see 'Fiat Abarth 1000 OTS Melbourne'.The description 'street' has many different interpretations.

Offline Pantdino

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Re: DCD carburetor linkages
« Reply #2 on: November 25, 2007, 02:01:32 AM »
I remembered that I shot video of an original 850TC and 1000TC in the Moell collection. I'm not at home at the moment, but when I get home tomorrow I'll try to look at it--it should show the carbs of both engines.


Jim

Offline Pantdino

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Re: DCD carburetor linkages
« Reply #3 on: November 26, 2007, 05:27:13 AM »
i looked at the video I have--
Herr Moell has a car labeled as "1962 850TC Nürburgring Corsa Specification".  The carb linkage is the "push toward the passenger side" type.'
He also has an original 1000TC, but I didn't film the exact year. It appears to have an IDF carb, with the "pull toward the drivers side" linkage.

The video is shot so that the bellcrank and linkage itself is blocked by the distributor, so I can't tell you much about that.

I don't think it makes any difference which type you  use. 

Jim Oddie

Offline zippyfiat

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Re: DCD carburetor linkages
« Reply #4 on: November 29, 2007, 06:40:56 PM »
Hi Jim, thanks for you info.  I think I have the answer.  I am pretty certain, although I can't find a photo, or anything in my parts books, that the 600D uses a linkage on the rocker cover so that linkage pushes, whereas the earlier 600 covers have a linkage that pulls to the driver's side.  I am sure I have a 600D cover somewhere here, and will have to go searching.   I looked at an 850 rocker cover I have, and it operates like the early 600.

The 600D linkage would explain why all the photos I have seen, show the linkage pulling.  It's because only the later cars with DCDs were based on the later 600D model...

Gil

Offline Pantdino

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Re: DCD carburetor linkages
« Reply #5 on: November 30, 2007, 07:18:13 AM »
I have the Autopress 600/600D repair manual and the Fiat factory manual for the 850
All the photos show the carbs with the "ball" for attachment to the linkage above the throttle plate shaft. So I think they would all be the "pull toward the drivers side" type

Jim

Offline viotti600

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Re: DCD carburetor linkages
« Reply #6 on: December 01, 2007, 12:11:44 PM »
I am pretty certain, although I can't find a photo, or anything in my parts books, that the 600D uses a linkage on the rocker cover so that linkage pushes, whereas the earlier 600 covers have a linkage that pulls to the driver's side.  I am sure I have a 600D cover somewhere here, and will have to go searching.   I looked at an 850 rocker cover I have, and it operates like the early 600.

Nope. 600D linkage "pulls" just like on the 600 & 850.

  The 28/36DCD is a particular variant of the 36DCD, and is known as a "progressive" carb, with the smaller primary opening first & the larger secondary opening later. This provides a little better fuel economy & slightly smoother driveability for street/traffic driving. The other 36DCD variants are more "non-progressive", with both large primary & secondary opening together (actually slightly staggered, but still close together). Less fuel economy, a little more grunt.

  I have 28/36DCD, 36DCD3 & 36DCD7 carbs. The ones I used on my old 600 & 850 a long time ago had a short flat throttle arm pointing up to the right, so the standard 600/850 "pull" type linkage could be used effectively. My DCD7 even has this type of arm, and it has a vintage dual-trumpet type of top intake similar to yours. You really should have some type of filtering over the 2 vent holes near the base/center of the trumpets - mine has small mesh screen domes on it similar to the large ones (my screen domes are flatter than yours, though). If I recall, these cover the air corrector jets?

  You can simply remove the long arm on your carb & replace it with something better suited to your needs. Lots of different crank arms here: http://piercemanifolds.com/linkage.htm

  I could swear I have some photos somewhere of the 36DCD setup on the 850tc/1000tc...I'll try to find them this weekend. ;)

-JS.
« Last Edit: December 01, 2007, 12:19:58 PM by viotti600 »
Jeff Stich
Norco, CA, USA