teach me the way of carbs

[Leesfer]

As far as I know, dual 40 idfs is the best setup for an 1800 or 2000 engine but is this too much for, say, a 1608?

What carbs work best on which engines? Can you dual any of the engines or only the larger ones?

[So Cal Mark]

you can run dual carbs on any of the twin cams

[Curly]

In my totally biased opinion (I run them on both my Fiats and a couple of British sportscars) the best carby set up is a pair of Weber 45DCOEs. They can be jetted down to run on a 1608 or anything up to the 2-Litre, or bigger if you wish. The avantage over a pair of IDFs is the straight inlet tract - no 90 degree bend , the disadvantage is they won't fit on LHD cars without without relocating the brake booster and master cylinder.
It's almost worthwhile going through the RHD conversion just to fit these lovely pieces of Italian craftsmanship.

[stefhahn]

As far as I know, dual 40 idfs is the best setup for an 1800 or 2000 engine but is this too much for, say, a 1608?

Well, dual 40 IDFs were the standard setup on the european version of the 1608. So it should work out well.
ciao,
Stefan

[mdrburchette]

I"m running 40 IDFs on both my original 1608 and higher performance 1608. They're just jetted differently.
Curly, I don't suppose there's any room for those carbs you have if we run the master cylinder without the booster, right?

[Curly]

Curly, I don't suppose there's any room for those carbs you have if we run the master cylinder without the booster, right?

I wouldn't think so - unless you rigged up some sort of linkage arrangement to reposition the master cylinder lower down or perhaps vertically. Anything's possible with creative engineering and I'm sure they'd look nice with gold plating too.

[Leesfer]

now are airfilters universal? I'd like to buy a couple of the oval perf filters from vicks but I'm not sure if they fit

[mdrburchette]

Are you talking about air filters for the dual carbs? You may need to use modeling clay to determine the clearance between the carbs and the hood. My flat hood car is only running horns do to clearance but my 71 has a small bump hood and can fit the turtleback air cleaner over the carbs. Check out Pierce Manifold for different filter heights.

[bradartigue]

I wrote a whole bunch of stuff on this topic http://www.artigue.com/fiat/Pubs/Artigu ... 124_MM.pdf

IDFs work well if you have the right pistons/cams for them. They require a lot of tinkering and finesse to get set up, but once set you are in pretty good shape. I think I emailed you - maybe it was someone else - how much I dislike IDFs. I do, but they have their place. Like on a racing motor when driving around the city at low speeds doesn't matter, or when you have infinite time to tinker with carbs that are rarely operating as well as you hoped. And if you've got hot cams sometimes they are the only choice for good fuel delivery (except for the DCNF, which is another dual carb option).

DCNF is a better carburetor imho if you can still find the manifold for it, it is more "tune-able" and shorter. There were rumors of the DCNF getting fuel starved on tight curves but no one who ever actually owned them seemed to have this issue. I ran them for a while on a modified 2 liter and loved them, the same motor that the IDFs were a tuning nightmare.

Still, though, in either case if you are running a reasonably stock motor then the late model FI system does a really nice job. If you are more aggressively modified you can put a Weber 36 or 38mm carburetor and rocket around and still operate very well in city conditions. 36 ADL is still IMHO one of the best bolt-on-and-go carbs for the slightly modified 2000cc Spider. It has a kick to it when that secondary opens that none of the smaller downdrafts or even the twins have.

I will submit this, though, at highway speeds the dual carbs are a riot. Torque for days. As someone at Pierce Manifolds told me once "It's enough carburetor [the IDF] for a large bus."