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Discussion Starter #1
Here's a tricky (or not) one for you expert's.
Fitted a New pair of 40DCOE's with the following:
Inner Vent 32
Outer 45
Pumpjet 45
Idle Jets 50f9
Main jet 130
Air Corr 180
Emulsion F2
Have Trumpets as cleaners
Living in Florida so always warm in the winter (80'sF) and hot in the summer.(95F)
No Cat as not required here.
Using a Strobe light the Carbs were set to TDC with timing mark P and cam marks exactly on the marks, then adjusted to the " F" mark for balancing the carbs.
Using non Ethanol fuel ( 89 octane )
New Electronic Dizzy and Bosch Blue Coil from Centerline.
New Alternator and Starter motor from Alfaholics ( uk) cheaper to import from the UK with the current exchange rate and no VAT.
The idle mixture screws have been set-up as per the Instruction from Weber and various youtube videos.
Engine starts - no problem and idles at 900 rpm when cool, once it gets to its working temp one or two of the cylinders start to spit back and
the exhaust starts to "pop" faintly as the rev's and speed start to decelerate.
Anyone here experienced the same problem and can pass on their wisdom ?
 

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F2 is a strange choice of emulsion tube for your application. F16 is the most common.
What does "outer" refer to? What is the full model number of the carbs?
 

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OK, "Here's the thing": (I learned that from one of the guys running to be our president)
We would do better getting you going if we had a bit more information.
1. What model carb. are you using. 40DCOE XX
2. Did you just have them worked on and have just mounted them?
3. How did you sync the carbs?
4. I don't understand your procedure using the strobe light. If you could see the cam
marks using a strobe light you must have a good coating of oil just about every where.
Now you could do that if you had a clear plastic valve cover.
5. Lastly and most importantly (according to Click and Clack ) what is the color of the car?
 

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Richard Jemison
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To start, the F2 emulsion tube has no place in any Alfa installation. This tube is for very high fuel flow or alcohol applications. As Ed said F16 tubes are the common ones to use. They won`t work.

Your distributor is an aftermarket one. Set timing to the max mark and leave it there.

What are the cam timing marks LCs? Spitting is generally caused by leaking intake valves or too much overlap.

What cams? Old early 1300/1600 Veloce cams had such a probled due to too much overlap and agressive lobe centers.
 

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Discussion Starter #5
Hello Guy's
Thanks's for the many replies ...
The Carbs are 40DCOE 151.
I was going by this recommendation from Selection and tuning of Weber DCOE carburettors
Emulsion tube Selection for a 2L ENGINE
Below is a table showing suggested emulsion tube type, for a given single cylinder capacity.
Cylinder capacity Suggested tube
250-325F11
275-400F15
350-475F9, F16
450-575F2

The outer Venturi or choke 45 came with the new carbs.
2. Did you just have them worked on and have just mounted them? I fitted them myself on aluminum mounts not rubber.
3. How did you sync the carbs? Using an air flow meter and adjusting each idle screw mixture to see how the engine responded to each turn of the screw.
What cams? Old early 1300/1600 Veloce cams had such a probled due to too much overlap and agressive lobe centers. Not sure - both were on the vehicle when I acquired it 4 years ago. It's taken me this long to get it running as it was virtually a "goner" when I bought it.
Set timing to the max mark and leave it there. The timing has been the "F" MARK.

I will fit an F16 to see if there is an improvement in the problems I have been having.
 

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Discussion Starter #7
Set the timing to the M mark at 5500 rpm - also ordered the F16 tubes, will update you when they are in place.
 

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Discussion Starter #9
Only about 1 degree anti clockwise turn on the dizzy.
Going to check both Cam numbers now as I can remember when I first looked at them about 3 years ago they had different numbers on them....
will revert.
Thank you for your question..
 

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Make sure your auxiliary venturis aren't loose or rotated. The 15s use a pointed screw with locknut to hold them.
 

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Discussion Starter #11
The Inlet Cam is a 105480520001 and the exhaust a 105200320000
I have the exhaust 105480520001 in my spare parts box given to me by the last owner (it has wear on the #4 lobe so i expect he changed it for that reason)
 

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Discussion Starter #12
F2 is a strange choice of emulsion tube for your application. F16 is the most common.
What does "outer" refer to? What is the full model number of the carbs?
The strobe light was only used for reading the timing marks on the front pulley sorry if I didn't make that clear.
I stopped listening to " Click and Clack " years ago - their humor and constant laughter was annoying!
 

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The Inlet Cam is a 105480520001 and the exhaust a 105200320000
I have the exhaust 105480520001 in my spare parts box given to me by the last owner (it has wear on the #4 lobe so i expect he changed it for that reason)
That is fine. You have a bit more lift and duration on the intake which is good.
 

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Richard Jemison
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Download a cam timing template from Centerlinealfa.com and set the cam timing to 104/104. With the
F-16s installed you should have a good running engine, however the main jet will likely need to be a 130.
 

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Discussion Starter #15
Morning all.
Lobes now at 104, F16 replaced the F2 and timing set to the "M" at 5000rpm , Main Jet is 130.
Car runs better but still has the occasional low " pop pop" sound during deceleration and at idle (traffic lights,STOP sign's etc. Could this be because I don't have a "Cat" on the car (Not needed in Florida) ?

Any more thoughts ?
 

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Popping on deceleration is not unusual with Webers.
 

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Hi, I had spitting carbs on my 89 spider 1600 with DCOE's, Turned out to be a stretched timing chain, after changing and resetting timing no more spits!
 

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Richard Jemison
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Are you using the 50 F8 idle jet? You do not want one larger, as well lean out the idle with the 4 adjustment screws before you do any thing else. Turn then in 1 at a time until that cylinder runs rough then turn iy out slowly until it just picks up again. Those screws only control the mix when carb butterflies are closed.

If your popping is in the exhaust, with the cams you have, lash is important as these cams are very slow ramp rate with too much off the seat duration for best valve event timing. Too tight lash makes it worse. Intake should be .018". Exh .019"-.020".

It might seem contrary re:"overlap", but with the exhaust cam you are using, retard it to 101-102 LC (about 1 hole on the sprocket). This will open the exhaust valve later to lengthen the power stroke (more Torque/Power), but it also increases overlap where that allows intake fuel/air mix to escape into the exhaust.. But if the performance increase comes with more popping of un-burned fuel in the exhaust you have to make a decision on which is preferable, a little more umph, or less noise.

Popping less tolerable? If it`s coming from your exhaust (asked in the first sentence) you can advance the exhaust cam 1 hole (105-106 LC ) and see if it improves the popping as that reduces overlap.But as well with these cams that will come with a cleaner/smoother idle and less fuel in the exhaust, along with a minor drop in power from your current 104 LC position.

Or you might have a leaky valve....

Bottom line, You need a wide band O2 meter to really know your carb tuning is correct, and a leak down check (not a compression check" too see if you have a truly sealed combustion chamber.
 

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Discussion Starter #19
I have 50 F9 fitted. Thorntid mentioned a stretched timing chain - how do you check that ?
Or should you change the timing chain after a certain time frame - as far as I know the chain is the original , 39 years old and over 110 thousand miles on the clock ....
 

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Timing chains don't stretch much and the adjuster is used to take up the slack. Take a picture of it and post it and let the experts give their opinions on whether you are getting ready for a replacement. If you do replace it, do not buy the cheapest one you can find. Their are some poor quality chains out there.
Having said that, the story of a slack chain causing misfires/spitting back is a new one on me.
 
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