New 1500 build + new 5 speed install

Agnelli

True Classic
I could never get the transition region to work well with F25 emulsion tubes. I'm currently using F36 tubes and I've heard that F24 tubes also work well for this application. Probably best to get the carbs cleaned up and in working order before swapping parts. I'm currently running 50 idles, 130 mains, 220 air correctors.
Helpful thanks Don. Checked my carb parts box, as luck would have it probably have all or most of what's needed to rebuild / refresh the DCNFs. Good info on the emulsion tubes. Also, my chokes are 30mm

Also, measured the distance between carbs on the Alquati vs. the Abarth intake manifolds. The Alquati places the DCNFs 26mm further apart, which does not permit use of the aforementioned repro linkage.
 
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fiatfactory

Steve Cecchele
if the reproed linkage is too short to join the carbs, just lengthen the tab on the cam drive side carby linkage that the adjuster screw / sprung pin (on the transmission side carby part of the linkage) are supposed to hold captive.

it's a little pedantic, but it makes a difference... although with your pictures I cant see the interlink very clearly... but the side of the linkage with the ball that your pulling on...should, and it definitely works best if it does... be pushing against the adjuster screw when it actuates the trans side carb...it shouldn't be pushing against the sprung pin (like I think your linkage is doing but the pics are not clear)

what happens if that is the case, is the carbs never sych properly, the initial off idle move compresses the spung pn and the balance goes off... off idle stumble isn't in the transition phase of the fuel circuit... it will more than likely be sychronization that's your problem IMO.

SteveC
 

kmead

Old enough to know better
This is a great thread. Thank you for bringing us along.

Tons of great learning and an excellent process displayed on how to get through the foibles of building up complex subsystems of the car.

Excellent work.
 

Joe F

Hi Miles, Lo Maintenance
This is a great thread. Thank you for bringing us along.

Tons of great learning and an excellent process displayed on how to get through the foibles of building up complex subsystems of the car.

Excellent work.
I whole heartily agree, Karl. I have owned X's since 1975 and a set of dual DCNF's for 5 years now and I am revamping my throttle linkage with knowledge I gained from this thread.
This site is simply amazing and has been for some time now.
 

Agnelli

True Classic
if the reproed linkage is too short to join the carbs, just lengthen the tab on the cam drive side carby linkage that the adjuster screw / sprung pin (on the transmission side carby part of the linkage) are supposed to hold captive.

it's a little pedantic, but it makes a difference... although with your pictures I cant see the interlink very clearly... but the side of the linkage with the ball that your pulling on...should, and it definitely works best if it does... be pushing against the adjuster screw when it actuates the trans side carb...it shouldn't be pushing against the sprung pin (like I think your linkage is doing but the pics are not clear)

what happens if that is the case, is the carbs never sych properly, the initial off idle move compresses the spung pn and the balance goes off... off idle stumble isn't in the transition phase of the fuel circuit... it will more than likely be sychronization that's your problem IMO.

SteveC
Steve -

A more clear photo of the carbs interlink may be found at the link below. I took a close look at it per your advice. This particular linkage has two solid screws from either direction of side with the ball activating the linkage (driving side). The transmission (driven) side has a curious round barrel capturing the end of the lever. Both screws from the ball side contact that barrel a bit off axis of the centerline of the barrel. In looking for the potential problem you identified, it didn't appear that the transmission (driven) side varies to the ball side. Butterflies on those appear to move consistently, without any play. I have not fully ruled out the linkage as the problem yet, want to further measure differences. Also, I wonder if the off axis adjusters put lateral pressure on the throttle shafts, which does not seem like a good thing.

Back to work on the carbs report: Pulled the idle mixture needle screws, idle jets, and main jets. Interesting to observe the left side carby needles were clean, and its main jets dirty. Just the opposite for the right side carby! Cleaned these, then reinstalled with fresh o-rings gaskets on the idle jets. Car starts great and idles well, which tells me the idle circuits are clean and working. Still has the sneezing and popping, and loads up / stumbles as it transitions into the mains. Downhill, pops a lot. Next steps:

Remove carb tops and verify / adjust float levels and check float needle valves. Order F36 emulsion tubes. Close air correction jets and perform tuning protocol. Set timing (new lamp arrived last night). I've read a ton about jetting and carb function here, on Mirafiori, Guy-croft.com (RIP), and Turbo124. Starting to learn about how carbs function, will post additional links about how emulsion tubes and air correction jets work. Still awaiting arrival of carb synchrometer.

 

Agnelli

True Classic


These you may find good to understand carb function and theory. Also, I will pull a plug, take a pic and post up.
 

Agnelli

True Classic
Photo of plug #4 att'd below. And the interlink mechanism so you can see what was described above. After those photos I did manage to clean the linkage area and carb bodies that were hard to reach with the air cleaner baseplates on.

Removed those, and carby tops. Fuel bowls had a bit of fine dirt at the bottom, not outrageous amounts I've seen worse. Removed fuel with syringes large and small and cleaned the bowls. Thoroughly cleaned the tops and inspected the floats and needle valves. All look good, valve free and dirt / corrosion free before cleanup. Measured the float ranges, one side perfect the other within a mm on one metric, made the tiniest bend. New carb top gaskets installed and banjo gaskets. With the tops off the carbs were not so dirty. The small air inlets above the idle jets were clear. Noted all four of the air correction are in the closed position.

Thanks NEG for the helpful manual, and to Karl and Joe and the rest of you supporters. To me the plug here below certainly doesn't look to be lean.
linky.JPG
linky2.JPG

plug.JPG
 

kmead

Old enough to know better
Definitely not lean. The tip looks good the plug ceramic definitely looks rich though not horrible. But you really haven’t driven it much so it is more rich than it should be. Though you may be seeing the richness of idling and not getting fully up to temp.

I wouldn’t obsess over it yet. Get it running decent and then move on it. Better a little rich and than too lean for now.
 

fiatfactory

Steve Cecchele
This manual is usually pretty helpful with nfo / dimensions. Has a full list or E tubes too, a translated copy of the italian manual, so some of the translations are only so-so.

That balance / interlink style s a PITA, you need to back one screw off to tighten the other...very fiddly to get the balance right, plus as you noted, the rod on the trans side carb isn't actually designed to be an adjuster, thats for a cable pull style setup on a single carb / nterlink for a boxer engine... and it's not sitting central so it won't make it easy for you to get right.


SteveC
 

Attachments

Agnelli

True Classic
Thanks Steve. Took some measurements, modifying the new preferred link will require adding ~30mm to the cam / driving side of the tab.

Meanwhile, the carb synchrometer just arrived.

And in studying the DCNFs, tuning guides, and parts diagrams ascertained I will need o-rings on the idle mixture screws. Tried the light green ones I had in stock which did seem to work on the idle jet mount screws but did not work on the mixture screws (they deformed under spring pressure load). Looked all over eBay and carby vendors then went with this McMaster Carr solution:

Chemical-Resistant Viton Fluoroelastomer O-Ring
1 mm Wide, 6 mm ID
9263K111

Bag of 25 for $8 vs. paying $1.25 + each.

Karl, completely agree with your thought above - get it to run right, that is the goal.

F36 E-tubes due to arrive on the 19th.
 
Here is a Weber manual specifically for the DCNF
Looks to be Chapter 13 from the Haynes Weber manual - good book. The appendix also has some useful DCNF information such as application info by part number and info regarding jets, tubes, etc by application.
 

Agnelli

True Classic
Thanks Steve. Took some measurements, modifying the new preferred link will require adding ~30mm to the cam / driving side of the tab.

Meanwhile, the carb synchrometer just arrived.

And in studying the DCNFs, tuning guides, and parts diagrams ascertained I will need o-rings on the idle mixture screws. Tried the light green ones I had in stock which did seem to work on the idle jet mount screws but did not work on the mixture screws (they deformed under spring pressure load). Looked all over eBay and carby vendors then went with this McMaster Carr solution:

Chemical-Resistant Viton Fluoroelastomer O-Ring
1 mm Wide, 6 mm ID
9263K111

EDIT - the 1mm wide is too narrow they've just arrived. Ordering 2mm standby will report back.

Bag of 25 for $8 vs. paying $1.25 + each.

Karl, completely agree with your thought above - get it to run right, that is the goal.

F36 E-tubes due to arrive on the 19th.
 

CnC79X19

True Classic
Ok Jim it's the 19th?? The arrival date of the O-rings. I was expecting big things from you today. Hopefully when I wake up for tomorrow's shift you will have already posted that it was a stellar, successful day and the engine (with those 39.5 valves?) is running like it came just off the assembly line?
 

Agnelli

True Classic
Ok Jim it's the 19th?? The arrival date of the O-rings. I was expecting big things from you today. Hopefully when I wake up for tomorrow's shift you will have already posted that it was a stellar, successful day and the engine (with those 39.5 valves?) is running like it came just off the assembly line?
Second set of O-rings still not right (too large ID). However, the F36's arrived today. Today: pulled the existing main jets/emulsion tubes/air correctors. Extracted mains and AC's from the F25 tubes. With a jewels loop, carefully inspected the mains, and mechanically cleaned them trying to be as gentle as possible. Jets now reinstalled. Changed the idle jets to 48's (the existing jets were 50's).

Removed the throttle linkage, affirmed butterfly valves on both carbs are even, and baselined the idle speed screw to one turn from fully closed per the Weber manuals. And baselined the idle mixture screws to open 1 1/2 turns from closed. Per SteveC, stood up the linkage lever on the cam box pivot shaft. I need to cut down the fixing bolt / nyloc on the pivot to enable free movement. The linkage is now set to (1) allow butterflies to close fully and open fully freely (2) optimize throttle effort.

I will cut that bolt tomorrow, then fire and measure vacuum across the barrels. I did a ton of reading on jetting, and maybe most important the tuning order protocol per that 1974 124 Sport Coupe Haynes manual (which is of course for IDF's but according to Obert is the best explanation of how to). I will image page 60 for the good of the order and post it up.

Stay tuned, pun intended.
 

fiatfactory

Steve Cecchele
turn the bolt around on the cambox lever and it may not touch the camcover....

F36 will be better than f25, so a good step.

45/47/50/52 idle jets on hand is always number one tuning tool for dcnf/dcnva etc... they spend a lot of time in the idle circuit so this is important and affects (nearly) the whole range of operation as they also control the progression and also spill fuel at wot... remember its cross section that matter for flow of fluids, and the difference/ increase in area/cross secton between 45/47/50/52 is quite a lot and not linear (as Pi is involved)

edit. I just grabbed an image from earlier in the thread and had a close look... your webers look to be the type with idle mix screws wth the cupped washer below the tension spring... in this image it kinda looks like the cup washer is cradling the spring... that's wrong. the cupped washer should be keeping the idle miture screw O ring in place. There are also maybe four different styles of idle mix screw (different taper and also different O ring positions) and check the tips of the idle mix screws, they get bent/ mashed up if someone is ham fisted and tightens them way too much

SteveC
 
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CnC79X19

True Classic
There you have it Jim. I don't want to use the term spoon-fed but I think Steve has offered it up closer than if he were there to do it himself. We all have faith in you!
 

Agnelli

True Classic
There you have it Jim. I don't want to use the term spoon-fed but I think Steve has offered it up closer than if he were there to do it himself. We all have faith in you!
Solved the linkage yesterday. Angles are right, and have full closed and full open butterfly valves. Quite like the swivel end Redline rod linkage. Test drive after the above jetting and cleaning: still has the inconsistent hesitation / load up issue above idle, though some improvement. Ordered correct idle speed o-rings, and more jets. Need to check for air leaks. Confirmed aux venturis are not leaking, so float needle valves may be functioning correctly..

All that said, the motor pulls well, no issue with power, it's quite eager. Just need to dial in the DCNFs.

Also ordered adapter for the STE-BK synchrometer. The large BK model is too big for DCNF40s.

linky3.jpg
 

CnC79X19

True Classic
Solved the linkage yesterday. Angles are right, and have full closed and full open butterfly valves. Quite like the swivel end Redline rod linkage. Test drive after the above jetting and cleaning: still has the inconsistent hesitation / load up issue above idle, though some improvement. Ordered correct idle speed o-rings, and more jets. Need to check for air leaks. Confirmed aux venturis are not leaking, so float needle valves may be functioning correctly..

All that said, the motor pulls well, no issue with power, it's quite eager. Just need to dial in the DCNFs.

Also ordered adapter for the STE-BK synchrometer. The large BK model is too big for DCNF40s.

View attachment 38792
Great news Jim, I'll cross my fingers for you. If we can help with anything let us know.
 
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