DMSA or keep dual DCNF?

[ScotcH]

I have a 78 with dual DCNF carbs with the red intake. Looks nice, pulls hard (I think?) but it sucks in turns ... starves of fuel, and that's no fun. Also has a lot of missing in the top end, but that might be ignition related. Car has an aftermarket header (4-2-1), and I think ANSA exhaust ... no idea about internals, but I suspect stock.

I also have a couple parts cars, a 73 and 74. One has a DMSA carb and matching intake in good shape. So I can use that to swap back to "kinda stock" 1.8. So:

- Someone mentioned I can add a fuel pressure regulator and that will help the starvation issue. Thoughts? I can also go to an electric fuel pump if that will help. How big FPR? 4.5psi?
- Swap the intake and carb to the DMSA (after a rebuild). Will this totally kill the performacne of the car, or will it be similar to the dual DCNFs?

edit: fixed DSMA -> DMSA ... duh!

[carl]

If the DCNFs are oriented with the two venturis front to back then they might starve in corners as they were not meant for that orientation, should be both venturis running left to right. That would not affect high speed performance in a straight line. I have a DMSA on my 2L spider and it works just great, this was the largest single carb Fiat used on the 124s. If you use the DMSA, get an 1800 intake manifold, the 1608 manifold is a two plain design and is a real performance killer. If you still want dual Webers, get IDFs.

carl

[ScotcH]

Thanks carl,

I have an 1800 intake from the 74 (the DMSA is bolted to it), so no problem there. I know WHY the DCNFs are starving ... I'm asking if maybe a pressure regulator will help alleviate the issue, and if It were to swap back to the DMSA, would I really loose any performance over the dual DCNF. I don't want to look into any other setups at this time ... want to use the parts I already have

[Daniel]

if you play with the float levels and have good psi on the fuel line you should be ok unless your racing the car.
DCNFs are a good carb and can be tuned nicely if you have issues on the top end my be fuel pressure.

[sptcoupe]

The "starving" could be because of jetting, float adjustment, needle valve too small, too little fuel pressure, or too much fuel pressure (foaming the gas)(you need a good pump and a decent fuel pressure regulator to keep the fuel at 2.5-3.0 psi), or ignition (does your tach jump around when it is missing?)

What jetting do you have?

[ScotcH]

Thanks for the info, guys ... I look at the spider every other week, so sometimes it takes a while to confirm stuff

But, I did notice that it indeed has an electric pump already. Mech pump is there, but unplugged (makes a silly noise ... going to remove it once I find a block off plate). I don't think there is a FPR, and I think the fuel filter cup is empty, unless it so full I can't see any fuel in it. It starts fine, and idles ok (misses occasionally). I think it's time to review the fuel system completely before I do anything else. No ide on jetting or needles ... I wouldn't even know how to measure that yet I know my BMW race car down to every bolt, but the fiat is a total black box at this point!

Btw, tach does not work, so no idea if it jumps when missing ... it's on the list!