my 77gtb has the following carb set up: individual air cleaners 135 main jets 55 idle jets 220 air correctors F36 E TUBES plugs NGKBP6ES stock ignition the car did not like the NGKBP5ES plugs, they were lean and the cars water temp was a few degrees warmer with them. i switched to the bp6's and the plugs are a near perfect brown-tan color. i believe the car can use a bit more fuel, so i plan on going to a richer aircorrector, say a 200. my ( old) 78308gts 125 mains 55 idles F36 etubes stock ignition NGKBP5ES plugs 55 idles open air cleaners. this car had some vaccum leak issues somewhere. i suspect the brake booster had a leak. car was always either too rich, or too lean. i could never get it perfect. the hotter plugs were a band-aid fix for the rich condition, which is a better choice from bieng on the lean side. my Dino 1974 135 mains 55 idle F36 E tube Crane x700 ignition ( dual) 190 air correctors stock airbox plugs ( unknown yet) this car has a burbble in the off throttle. also, right at the transition from the progression to main jet it has a slight hesitation. idle is clean and wide open throttle is fun. car will spin the tires loose in 2nd and 3rd gear. my plan is to pull the plugs to read them, go with NGKBP6ES plugs, and order the individual air cleaners. i believe the 190 air correctors are too rich, so i am going to switch to 200's and see. i will have the 220's from the GTB to use also. car smells rich at idle, but just a tad rich, just enough for me to want to perfect it, but not too rich as to indicate a problem. question: the dcnf40 's on the dino have different tops and velocity stacks that are part of the carb housing. i will attatch pics, but i already know that the Pierce Manifolds individual air cleaners from my GTB will not properly fit the webbers on the dino. it is not possible to use the rubber gaskets at all. am i to assume there is another style of individual aircleaner for this webber top? or must i assume that i will have to replace the tops on all 4 carbs??? i would really like some help with this question as i need to place the order Monday for the parts. also there is much less airflow through the dino engine compartment , so i am going to watch and see if the engine heat grossly affects the way the carbs idle and run in traffic in the summer heat. will post updates. the gts /gtb's have enough slots in the hood to allow better airflow. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
I'd bet that the carbs on the 308GT4 have been replaced with a set of 4 each of the 40-DCNF-12 and the specialized linkage bits were moved over from the original 40-DCNF-35/36/37/38 set (or whatever WW/XX/YY/ZZ set is "stock"). I had bought a set of the 40-DCNF-12 for my ex-308, and they also had the non-removable airhorns, and the other difference was the top cover of the carb is held onto the main casting by only 4 screws (instead of 5) -- is your GTB 5 top cover screws and the GT4 4 top cover screws? The Weber "part number" might also be stamped into the outside forward-facing flat vertical surface of the fuel bowl. IIRC someone mentioned that SuperformanceUK could machine the 40-DCNF-12 to accept the stock 308 airhorns, but I don't know the details.
great, i have never even heard of the -12's. ill do some looking around. i may as well just buy a set of used dcnf 40's.
Or just leave well enough alone. It will break the rear wheels free in 3rd? Why do you need different air cleaners?? I'd say it's working fine! Birdman
I bought a set of new -12s and the stock 308 air horns and air box fit fine, no mods; the -12s also readily accept the Pierce filters no mods. Many pics in 3.2 carb conversion threads. As pointed out, the -12s have a 4 screw top. I believe that the integral stacks may be another dash number, but this IS an italian carb.
Russ, are you back?? How are things? Michael, hesitation in the transition zone between idles and mains is often a sign of poor synch. Birdman
so nice to see you posting here! i hope all is well with you! the airhorns on these carbs are part of the whole top of the housing. the Pierce Manifolds air filters wont fit with the rubber seals installed. i assumed the flared airhorns are preferred over the straight ones. the difference in the air correctors seems to be part of the issue with the the way the gt4 sounds and feels. the gtb is always on the lean side. i have a friend here that has been having ongoing carb issues with his 79gts. i am planning on installing fuel pressure guages on both cars and see what the pressure delta is for both as an average and compare the numbers to his GTS. i changed the fuel filter on the gtb yesterday, however, the weather has been too bad to play with it and i still have the 2 girls here from out of town staying here. Birdman, will check the sync....... and ignition timing.
Russ -- Who was your source for the -12s? Did they come with some other air horns that you discarded? (I'd still swear that mine were -12s too -- at least that's what's listed on my receipt from Pierce Manifolds and in my memory of the marks on the fuel bowl surface.) Another difference that I just recalled between the 12s and the stock F set is that the stater (choke) valve lever action is reversed (as shown in michael's photos) so the stock F choke cable system can't be used to actuate them (but not an issue really).
Howdy all - not back yet, still 68 km north of Baghdad in 117 degrees, but here with my Ferrarichat buds even while being mortared by insurgents through the miracle of the internet. I bought my -12s new in the Weber box, stock 308 airbox and air horns from Bill at GT Auto Parts in Az. They DID NOT come with other integral air horns. I've used 3 variations, the stock 308 rolled air horn, the tall meshed Superformance trumpets and Kermit's low rise - all fitting without mods as I've shown in the previous threads. Yes - the starting enrichment lever mechanism is reversed, but I didn't even hook mine up and it does fine. All of the parts diagrams I've seen do not show the squarish integral air horns as on some DCNs or early DCNFs I have heard that some induced hesitation in transition is not uncommon, depending on year and jetting, especially later as mixtures leaned out. A slightly richer idle may make that hesitation go away, but at the expense of a bit richer low end running and emissions best to all from Babylon Russ
Russ - Mine came in an "official" Weber box too so I'm not accepting that evidence . Since you were buying a "package" from an experienced F supplier, I'd still guess that your 12s have been modified to use the seperable, stock 308 airhorn. Stay safe...
mine are 2 1/2 inches tall. if you tell Pierce what carb and what Ferrari you have they will match them up for you. best, Michael.
