Best Carb 4 Drivability ?

J

jeffsc

Daily Driver
Hey guys,
I am thinking of replacing my dual dcnf40 carbs with a single carb for better drivability. This car goes great as long as I'm on the go but often sputters and dies when I get off the gas, requiring a throttle blip until the idle stabilizes. The main engine modifications by PO are serra big valve head, no emissions, bottom end is stock, I don't know about the cam.

I want good drivability, I'm ready to chuck them and replace with a single carb if that will fix the issue, hopefully not losing to much power in the process.

I figure my options are
1) Find some local carb guru and pay them whatever it takes to adjust the existing carb settings until they are right.

2) Replace with simplier 1 carb setup gaining drivability.
If so which ones are best ? How much power will I lose ?

or 3) go with stock FI

I'm thinking the single carb is the cheapest and simplest route to go, and the local fiat mechanic recommends also. But I'm also willing to pay some guru to adjust the dual carbs if sufficient behavior modification is possible. I appreciate any thoughts the braintrust here has even though I've asked before...sorry if I sound like a broken record, I only have the time, expertise todo simple stuff and just want to drive my X !
Thanks !
Jeff
 
carb gurus are becoming an endangered spieces try to raise the idle a little, mine HAS to idle at 1100 to idle at all
 
BB 4RE has a single 36 DCNF...

....Excellent power. Just need to have a single DCNF intake for it, though.
 
BlueX (Scuderia Fiat) has

a single 40 DCNF. Was like having dual carbs, but without having to sync them up. Took me a little tweaking to get the idle, full open, and daily drivability worked out, but once I did, man, it was nice. She will be mine again one day.
 
Plenty of cars running around with 2, 3, 4, or even 6 DCNFs that idle and drive just fine. It's a matter of selecting the right components for the intended use. The parts used in a motor have to work well together.

In order to modify an engine and improve its output without severely compromising drivability the engine has to be considered as a package. I suspect that a carb change alone will not completely solve the issues you're experiencing.

///Mike
 
Just one "FI" comment from an old "Carb" guy...

If yur gonna go with a STOCK FI it would be best to start with an FI car... but otherwise, you'll need to replace most of the wiring harness, get an additional FI harness, and then all the componants along with a high pressure pump. A lot of work...

The best of both worlds would be to use an aftermarket FI like MegaSquirt...

Let me know when ya wanna ditch the duals...
 
34 DMTR

Hi Jeff,

dual DCNFs can be made to run nicely, as Mike states, that also depends on the rest of the engine.

However, the duals will never be quite as nice as a single 34 DMTR.

OTOH, if your driveablility problem has to do with a very hot cam, your idle will be worse with the single carb, resulting in a very high idle.

If you have a carb guy that you can go to, by all means, try that first.
First step is to see what kind of jetting you have in the carbs and post it here. If there is something completely wrong, we will tell you.
 
Almost.

One correction: The stock F.I. wire harness piggy-backs on the stock wire harness, everything needed for F.I. is in the add-on harness. So if you were to go this route, you would only need to get the F.I. harness. Typically it goes from the F.I. computer to a dual relay, and around the engine bay.:nod:
 
I notice that

BB-4RE has more pep than my 86 FI car.
Probably also has something to do with the lack of AC and emissions garb as well. But I agree the 36DCNF rocks! :headbang:
 
Double correction...

You're absolutely right about the 'add-on' FI harness, but the late model harnesses include wiring for the fuel pump (and subsequent fuel pump relays!) and manifold fan wiring, plus the (non-related) AC wiring.

Granted, this can be added but with some hassle. (as the fuel pump relays are inside the spare tire compartment so you'd have to run the wires) Hence I think Tony's point.

Still, I don't think it'd stop me from doing it if that was my goal...
 
Thanks, won't give up on duals yet

Thanks for feedback, my X is at the only local fiat mechanic I could find changing the front ball joints and a motor mount and some bushings-but he doesn't want to mess with the carbs, so today I started going down the list of carb "guru's" to find someone who can help me get this right when I get her back.

Anyone who knows any good in Tampa area pls let me know.

Thanks, Jeff
 
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