Topic: Advise on A112 70HP+40DCOE

[bibito]

Hello, everyone,
recently decided to go with the weber 40dcoe on the standart A112
abarth 70HP engine.
Please, advise need adjsutsments and possible pros and cons of that set up.
Thank you.
Lubo

[Pantdino]

Hello, everyone,
recently decided to go with the weber 40dcoe on the standart A112
abarth 70HP engine.
Please, advise need adjsutsments and possible pros and cons of that set up.
Thank you.
Lubo

I don't recall seeing a 40DCOE on a 4 cylinder engine with the standard Autobianchi A112 / Fiat 850 style single inlet head. Those are usually seen on "4 canal" heads, either Abarth, Aztek, or other aftermarket type, and use 2 of them.

Does someone make an intake manifold for that?

I saw one on an Abarth 695 motor and 2 liter Alfas run a pair of them, so it should work.  But you'll probably have to put the car on a chassis dyno and have someone who knows Webers well do the venturi, jets, and airs to make it run right.

Jim Oddie

[Carlos]

Hello pantdino!

Have a look on this side!
newbielink:http://www.abarth-motorsport.nl/ [nonactive]
There you can find inlets for one 40DCOE!

Greatings
Carlos

[guy moerenhout]

a intake manifold of this type was made for the A112 like one piece valvevover/intake on the 58 hp.The difference with a single one is only 2 our 3hp but easy regulation.On the old mini you have the same set.You can better play with the venturis.But fuel becomes hotter and for this the changes it back.Hot fuel =loosing power and vaporlook but is a nice looking set and drives very good.

[Paul vander Heyden]

I have tried using a single side draft Weber on several customer engines, and I have NEVER made more (usually less) HP than with a two barrel downdraft carburetor.  The preferred down draft is a 36DCD7, although I have also done successful installations of 38DCNF, 40 DCNF and Solex CCI 40-42.

I have intake manfolds to suit any of these carburetor combinations.

Paul Scuderia Topolino
www.scuderiatopolino.com

[bibito]

Thank you, Paul, Guy,
the reason beening that it looks better and should perform about the same, + a have a few of those/40dcoe/  I have to use.
Any ideas on the ventury and jet sizing, cams..
Paul perhaps you have a cam to suit.... ? and I still plan on getting those ARP's...from you
so might just combine them, so if you have any ideas pleas,share.
Thank you,
Lubo 

[zippyfiat]

Hi Lubo,

I have had a few people tell me that they tried the sidedraft Weber DCOE only to find that the engine ran poorly after ("like crap" according to one).  They all said they immediately switched to downdraft carbs and the engines ran much better.  The DCOE sure looks good but you should be prepared to be disappointed with the results.  The design of the stock Fiat cylinder head just does not work well with a sidedraft carb. 

You can still find a DCD carb with a bit of patience, but finding a "correct" older version (eg., DCD7) can be harder.  You could always try a DCNF as Paul suggests.

Gil

[Pantdino]

Hi Lubo,

I have had a few people tell me that they tried the sidedraft Weber DCOE only to find that the engine ran poorly after ("like crap" according to one).  They all said they immediately switched to downdraft carbs and the engines ran much better.  The DCOE sure looks good but you should be prepared to be disappointed with the results.  The design of the stock Fiat cylinder head just does not work well with a sidedraft carb. 

You can still find a DCD carb with a bit of patience, but finding a "correct" older version (eg., DCD7) can be harder.  You could always try a DCNF as Paul suggests.

Gil

Anyone know why a side draft does not work well?
I have read that the fuel has to make a sharp turn, which is a problem.

Also, having a long distance between the throttle butterfly and the intake valves will tend to tune the engine for lower- rev operation, which is not where these engines make power.

Jim

[zippyfiat]

Jim, I think that is a question that Paul would be a good one to answer.  I believe the reason is that because of the extra 90 turn and longer runner the fuel does not stay in suspension properly.  I think that by the time the fuel/air gets into the combustion chamber there is actually gas in liquid form that washes onto the surfaces of the chamber.  I might be somewhat off on this, but it's something like that.

To compound the problem, with the design of the Fiat head, cylinders 1 & 4 always run leaner than 2 & 3 because of the extra distance the fuel/air mix has to travel.  It is my understanding that a sidedraft carb. only makes this situation worse.  PBS used to make their "stager" cams to delay the fuel charge getting to cylinders 2 & 3.

The only successful application of sidedraft carbs is with two sidedraft carbs.  These setups (PBS, Abarth OTR for example) have intake runners that are quite short and are of equal length to each cylinder.  There have been some heads where people have welded up the stock opening and added 4 new ones for dual carbs along with a custom intake manifold.  I've seen 2 or 3 of those on ebay in Germany in the past few years.

Maybe some expert out there will correct what I've said or add to it.....

Gil

[bibito]

Thank you, Gil,Jim,
for shearing your thoughts.... but still,
is there anyone, in the forum, that has been or still is using that set up?
I already got the manifold , so I guess I'll have to give it a try, any practical tips will be welcomed thou.

Lubo

[guy moerenhout]

I use it on a 850 spider and works very well.Use very small chokes 25 our 28 .The adventage from this set is that you can find all parts easy for a 40 Dcoe.Start with 125 /190.Think on a NSU 1000 TT our TTS,this have also very long and high intakes.Also the first prototype  A112 (with TCR head)had long intake manifold and over the engine.

[bibito]

Hi, Guy,
I have the manifold with holes for 38mm, I guess 38DCOE,
should I be looking for a 38DCOE or just use 40 and change the chokes and jets accordingly.
Could you please, post some pictures of your car with that set up.
Thank you,
Lubo

[guy moerenhout]

you can open the holes to 40.The 38 dcoe was use on fiat 2300 S.Car is sold .A populair set for the A112 first serie was a intake manifold and valvecover in one piece for the DCOE.

[grant gauld]

I also made a 40 DCOE to work very well on a 850 sports motor (903cc).The car won its class in a few hillclimbs and a 4 day classic rally.You just have to find someone who is genuinely skilled at jetting when you run the motor on the rolling road.I made a large kidney shaped inlet port in the head,about 75% larger (to suit the manifold).
 I think I have tried 5 different carbys and I do prefer a 36/36 DCD,but if its what you want,go for it.
 A pretty common cam grind like a 30/70/70/30 worked well with the DCOE.If you can reduce your cars weight this will also make a very big difference.
Grant

[trevor]

Re Guy's comment (reply #11) re A112 with TCR head; see photo; one wonders how vibration effect on dcoe's was controlled, if possible ?
Trevor