Author Topic: Sidedraft carburetors  (Read 2588 times)

0 Members and 1 Guest are viewing this topic.

Offline zippyfiat

  • 2000 cc
  • *******
  • Posts: 185
  • 500
Sidedraft carburetors
« on: May 31, 2007, 07:56:19 AM »
I am wondering if anyone has had luck with a single sidedraft Weber carb. on an 850/A112 head?  I have heard lots of negative things about the manifold Alquati made and as a result, I sold the one I had without ever trying it.  I have a PBS one that I'd like to try.  It has a short intake runner which should help?

Thanks,
Gil

Offline Paul vander Heyden

  • 2000 cc
  • *******
  • Posts: 179
    • Scuderia Topolino
Re: Sidedraft carburetors
« Reply #1 on: June 03, 2007, 07:44:30 PM »
Gil,

My own personal experience has been that an intake charge does not like to turn a 90 degree bend, regardless of the motor or the installation.  Yes, the 40DCOE/PBS intake manifold will work (looks impressive too), but it is probably not the best carburetor intake manifold combination for this style of head.

There are a number of better performing alternatives.  In the main a two barrel downdraft combination will give a better airflow.  For years the favorite has been  the 36DCD type carburetor [two versions a) progressive linkage b) non-progressive linkage].  This carburetor with 29mm venturis is a good combination.  For all out racing, the non-progressive is preferred, however for street applications the progressive type may have the advantage with somewhat greater economy at part throttle and the same performance at full throttle. 

Weber makes another series of carburetor referred to as the DCN series.  This can be anything from a 36DCN, 36DCNVH, 40DCN, 40DCNF, even a 42 or 44DCNF.  Keeping in mind that the 29mm venturi will determine the actual airflow through the carburetor.  This  carburetor requires different intake manifold as it sits in-line with the cylinders.  Some say that the carburetor starves for fuel on right hand corners, but this is sort of an urban myth.  With the float level properly set, this type of carburetor works very well.

FInally, there is the Solex 40-42 CCH.  This little known and regarded carburetor was made by Solex in the 60s-70s purely for motorsport applications.  It is very basic, but very effective.  In addition it is cast in aluminum, versus the zinc alloy used for most Webers, so weighs considerably less. (Note: Some DCN Webers for Ferrari applications were made in aluminum as well).  It was used on German Ford V6 motors extensively as well as by Saab on the V4 powered rally cars.  It has replaceable venturis similar to the Webers mentioned earlier.

All three carburetors have a four circuit configuration consisting of an idle circuit, a cross-over circuit, accelerator circuit and a running circuit, so tuning is pretty much the same. 

All of these can be fitted to the Fiat 850/A112 type head with the correct intake manifold. 

Offline ChrisD

  • 2000 cc
  • *******
  • Posts: 156
Re: Sidedraft carburetors
« Reply #2 on: June 22, 2007, 12:48:51 PM »
From what I read, it is better to use the 36DCD, right? What if we use just one 40DCOE in a 1050 engine? will it be better than the twin 40DCOEs? If te engine is not highly tunled like a race engine, is there a chance the 40DCOE can chocke the engine with fuel? I am curently rebuilding a 1050 engine and trying to find the best carb for it. 40DCOE seems to be easier to find than the 36DCD, but if it doesn't work well I guess I'll go for the 36DCD. Any sugestions???

Thanks,
Chris
Fiat 600 Abarth

Offline Paul vander Heyden

  • 2000 cc
  • *******
  • Posts: 179
    • Scuderia Topolino
Re: Sidedraft carburetors
« Reply #3 on: June 24, 2007, 03:54:23 PM »
Chris,

Yes, the DCOE will be easier to find than a good 36DCD.  The DCD will likely be more expensive as well, as this is the carburetor that all of the historic racers need.  You will find them on older model Fiat automobiles, as well as some Volvo and Cortinas.

The problem with a DCOE is that the air stream has to make a rather abrupt right hand turn.  This short radius will tend to pull fuel out of suspension and drop it to the bottom of the intake port.  Overall the performance on a street car will be OK and it looks much more impressive than the DCD. 

Good luck,

Paul Vanderheijden
Scuderia Topolino

Offline ChrisD

  • 2000 cc
  • *******
  • Posts: 156
Re: Sidedraft carburetors
« Reply #4 on: June 25, 2007, 08:21:14 AM »
I managed to find one from a Cortina. It is in bad shape, but with a little cleaning and a repair kit I belive it will work ok.
What is the best to use in this one? A K&N air filer box or a benturi?

Chris
Fiat 600 Abarth

Offline Paul vander Heyden

  • 2000 cc
  • *******
  • Posts: 179
    • Scuderia Topolino
Re: Sidedraft carburetors
« Reply #5 on: June 30, 2007, 03:00:24 AM »
Chris,

If you are running on the street, use a filter, ANY FILTER, as to not do so will just wear things out faster.

Good luck.

Paul Vanderheijden
www.scuderiatopolino.com

Offline ChrisD

  • 2000 cc
  • *******
  • Posts: 156
Re: Sidedraft carburetors
« Reply #6 on: October 01, 2007, 02:11:22 PM »
Anybody has the part number of a K&N air filter for the 36DCD cabr? I think it is 56-9070, just need to check it!!!

Thanks
Fiat 600 Abarth

Offline marin

  • 1800 cc
  • ******
  • Posts: 31
Re: Sidedraft carburetors
« Reply #7 on: December 13, 2007, 10:35:31 AM »
the sidedraft  (DCOE) carburetors are best for "in line" engine and  idf and other carburetors are bestz for  v-engines and boxer engines ,.. you just need to find a jetting.exe software
tu ajust the carburetors