69 124 Spider dual Weber DCNF set up? ADVICE!

[69original124]

I would really like your first hand experience if going with the DCNF set up is seriously a good way to go. I was assured by a local owner this was a good set up, as he was going to do the work. But in talking with a few professional mechanics with many yrs of experience the DCNF route is less than ideal.

The better route seems to be going with IDF's. More consistent & reliable. (?) I have lost nearly 5 months due to a series of "set backs" because of the locals advice.....I won't bore you with the details.

I would just like to get some 1st hand exeprience from you guys. I would consider selling the DCNF's if needed.

[sptcoupe]

I have fitted three motors with DCNFs, and while they are a good carb, they are much better suited for a transvesely mounted engine (ala a Lancia or X/19). The positioning of the main jet pick up in the float bowl on a DCNF will cause fuel starvation under even mild cornering g's, because the fuel pick up will be momentarily uncovered as the fuel climbs up the float bowl sides under cornering forces in a longitudinally mounted motor. Not much fun when you are into a corner fairly hard and suddenly lose power! It will slo tend to uncover the fuel pick up port under hard braking, as well.

Take it from first hand experience - use the IDFs on a longitudinally mounted engine, the DCNFs on transversely mounted motors.

[69original124]

Thx!! sptcoupe ...I have not heard this particular comment yet, so I really appreciate your fast & insightful reply!!

I also hear the tuning of the duals can be an issue as well as configuring a throttle cable. (?)

[sptcoupe]

Have a look at the post right above this one - Dual IDF Tuning Guide. Take care of the fuel pressure, throttle linkage, float settings and jetting, and then it is a fairly straight proceedure to balance and synch them and set the idle mixture.

What other performance mods have you made/intend to make?

[69original124]

Sorry I was not more clear.......I understand the DCNF's are more difficult (than IDF's) to tune, sync, etc. for a 124.

In the end, a whole lot of mods I hope. Headers, cams......not sure yet. Maybe move to a 1592 or 1800 and build the entire engine.

[Fi8spider]

IDF's are definately the go over DCNF's for a Spider.
Personally I have DCOE's on mine which delivers a tad more torque (negligable really for a road/club track car) but I dont have a brake booster in the way because of it being RHD.

I have no experience with throttle cables on LHD cars so count me out on that one.

Regarding the myth that they are hard to tune, well an area often overlooked are the butterfly shafts which can bend (twist) over time if the full throttle screw wasn't adjusted correctly by previous owners with over zealous right feet. This twist in the shaft will make the butterflys sit uneven when closed and will result in many, many hours of unsuccessful tuning if not detected.

If it were me - When I'm not familiar with the condition the carbies I've just bought, they get a strip down, clean and a rebuild kit put through them ensuring I change the needle and seat and re-set the float levels as per spec.

I inform myself on the correct jetting for the application I'm faced with and then I hand the car over to my carbi specialist who has and knows how to use a carburetor synchronizer. You will usually find that long established Alfa Romeo dealers have this tool as they were a special tool supplied by alfa to tune the 105's, alfettas, sud and 33's , otherwise most carbie tune specialists will have one.

The reason I'm am harping up about the tuning aspect is because many times the effort is put into buying all the parts fitting them and leaving them as is. Unknowing to many that with a proper tune and set up you will get maximum fuel economy and performance out of your carbie investment.

Second to all of this if you have no need for your current twins I have a little Fiat 128 I would love to see with a set of DCNF's on it.
Good luck with it all.

[69original124]

any & all input is appreciated!!!

[Turbofiat124]

I have fitted three motors with DCNFs, and while they are a good carb, they are much better suited for a transvesely mounted engine (ala a Lancia or X/19). The positioning of the main jet pick up in the float bowl on a DCNF will cause fuel starvation under even mild cornering g's, because the fuel pick up will be momentarily uncovered as the fuel climbs up the float bowl sides under cornering forces in a longitudinally mounted motor. Not much fun when you are into a corner fairly hard and suddenly lose power! It will slo tend to uncover the fuel pick up port under hard braking, as well.

Take it from first hand experience - use the IDFs on a longitudinally mounted engine, the DCNFs on transversely mounted motors.

I've heard that as well. That there are front wheel drive carbs and RWD carbs. Or depending upon how the carb is positioned.

Someone posted somewhere they installed a 32/32 ADFA from an 1800 Spider in place of the 32/32 DFTA on a Yugo and said it worked well. Despite both are 32/32 carbs. I don't see what the advantage would be.

Based on both carbs, the float pivots from front to back.

I can see how the way the float is positioned could be affected from hard corning but looks like the same thing would happen under hard acceleration or hard braking.

[Fi8spider]

Based on both carbs, the float pivots from front to back.

I can see how the way the float is positioned could be affected from hard corning but looks like the same thing would happen under hard acceleration or hard braking.

That depends which way they are mounted.
In this case where the carbs will be mounted on a "124 BC" type manifold, the DCNF will have the float pivot laying east/west in the front of the carb. On an IDF it would be North South on the outside of the carb.

DCNF


IDF


I've only the word of people with previous experience to run by as I've never run twin DCNF's on a North/South motor.

But the way I see it, Fiat would have fitted DCNF's over IDF's on the 124 BC if they were better suited to the application.

Neither diagram shows what sptcoupe mentioned about the main pick up "in the bowl" but you can see from the main jet positioning on the DCNF that he is correct.

[69original124]

GREAT info, thx!!!

Looks like I am moving ahead with selling these if anyone is interested. May list on eaby if the right offer does not come along soon here.

[69original124]

Been focused on lots of other stuff.......so throwing it out there again to sell this set up.

Anyone?

[fiat218]

sucks that i got the DCNF too then, but my mechanic told me that he can fix the stall out on them. i haveno idea so when the time comes we will see