Question for all the dual DCNF carb users.

[Warren Horby]

I am going to install dual carbs on my scorp ( I am going to give them a try before deciding to go to F.I ) and I just want to know what every one is using for jetting and choak sizes for the 40mm carbs. I have HC pistions and 40/80 cams and header.I have used the Weber book to get me in the ball park but I hate the fine tuning part. Anny help will be appreciated.

Thanks in advance.
Warren

[Allen Lofland]

YO ....I have a 77 with dual 40 dcnf's 2 liter engine with 9.8 pistons 40/80 alquati intake cam and stock lancia 2 liter exhaust. tuned ansa header and exhaust. Carb jets are 32 chokes--- Idle's 60----Air's 200---Fuel main's 125's....She runs real nice. I am at 1300 above sea level, Wichita Kansas.
Use 91-93 octane at pump.
You dont mention engine size, I guess you have a 1800. these settings should be ok for the 1800 with HC pistons and cams also. You might see what others are using. before investing, What do you have already with the carbs ???

[Warren Horby]

In my carbs I have 34mm choaks, f22 emultion tubes, 200 airs, 120 mains and 60 idle jets. I don't think the emultion tubes are correct, I will have to double check with the weber book. BTW Allan, I don't have Vac advance on my Dist either.

[Allen Lofland]

Warren: What did you carbs come of off ...... they may be ok that way. My emulssion tubes are F24's but yours might work depending on what they wherer set up for originally. Is you engine a 1800 stock.

[Warren Horby]

My carbs and manifold came from a 124 sport. I had the manifold modified so that it would work properly on a Scorp. Like I said, my motor is stock appart from the pistions, cam, and headers. I am in the process of making a filter box and then I am going to instal the carbs. Will the stock throttle linkage work on the duals?

[DJ]

You can download a copy of the Alquati instructions for their dual-DCNF manifold (Italian text) in the files area here:

http://www.lancisti.net/pafiledb/pafiledb.php?action=file&id=109

The top set of specs is for the NA engine and are interpreted below. The lower set of specs have been modified by hand by Chad (Monte Hospital) and is for the Monte with 2 liter.

Choke: 33 mm
Air Corrector: 0.200
Main Jet: 0.125
Idle Jet: 0.065
Accelerator Pump Jet: 0.045
Emulsion Tube: F22

Most common knowledge I've been able to dig up AND my experience has been that your chokes really should at 32 MM for a 40 DCNF, especially on an 1800. With anything larger you may gain a little way up on the top end but you lose a lot of torque. This is the first thing that I would change. It sounds like a small difference but this can make a big difference in torque and drivability.

I'd also say that your main jets are a bit small. I'd stick a set of 0.125s in as a starting point just like the Alquati specs call for.

The F22 emulsion tubes should be fine. Some sources claim that F24s are more appropriate but Alquati specifies F22s and you WON'T see much difference at all between them. In fact, it's so subtle that you may not be able to discern it at all.

I'd stay with the 0.060 idle jets until you get it set up and running. It should run fine with those. After you get it running, if you don't like the enrichment at idle you can adjust it from there. One thing that is critical about the idle jets is the difference in size between them and the main jets. If you get a flat spot around 2500 rpm, you need to get the sizes of the jets a bit closer together. This is the point where the carb transitions from the idel jets to the mains and if the difference in sizes is too great, you'll get a stumble. You can tweak this out with smaller mains or larger idles. With 0.125 mains, I'd adjust the idles first.

Hope this is helpful.

[DJ]

...Will the stock throttle linkage work on the duals?

The Alquati manifold has a spot to mount the Scorpion throttle linkage assembly. If your manifold doesn't have a spot for this, you may have to fabricate a way to mount it.

Alquati also provide a modified pivot arm and connector rod to replace the ones on the stock setup. The new pivot arm provides a longer throw.

You should be able to set it all up without too much trouble, though. Do you have the inter-carb connecting linkage?

[Warren Horby]

Thanks DJ.
My manifold is an Alquati and I have had it modified so I can use it on a Scorp. I printed the file off and it will be a great reference. I am going to see if my Italian friend can translate it for me.

[junior]

Hi there everybody,

I am now to the stage where I have bought 2 brand new 40 DCNF's for my S2 montecarlo. I was feeling impulsive, and maybe I should have waited to have found some good second hand ones, because they were not cheap. These are latest edition DCNF's, which should not have any problems going round corners, or so I was told. I have a rough casted inlet manifold made up which appears to fit the montecarlo (no modifications required). I now need to know the exact angles that have to be machined on both ends of the inlet manifold. Does anybody know these? Or better still have drawings? I suppose any montecarlo inlet manifold will be the same angle as any other montecarlo inlet manifold.


Regards to all