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A bit late to this topic, but thought I'd chime in.

I believe the problem with the stock 102 setup, at least in large part, is on the intake side of the air canister. If you look at the opening for the incoming unfiltered air, it is, imho, way to small to support any sizable volume of airflow. The opening's area is no where near the area of the bellows end opening. I've wondered if even drilling larger holes that run along the side of the opening would help. I think the overall fix would entail a bit of customization on the one end - a good fabricator should be able to both widen and increase the height of the opening while still maintaining a mostly stock looking unit. Just a thought, but one I've been thinking about. My engine is at the machine shop and the pistons made for the rebuild are larger then +4 - so the volume of air is going to be greater and having heard Ken's story (while admiring his car in person) starting wondering "why" and what happens if this hits me.
 

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Chokes

I think I have set hares running with my description of the effect of different size chokes on my 2600 . This was purely to illustrate how in my case restrictive air flow causes loss of power as revs increase.

For the 2000 32mm chokes seems to be correct .

Have a look at this old thread from Marc Guisti where he spent a lot of time finding the correct jetting for his 2000 .

http://www.alfabb.com/bb/forums/1900-2000-2600-1950-1968/161591-good-great-sprint-parts-needed-4.html

For some reason unknown to me 36mm is correct for a 2600 - this was the original choke size for the Weber set up on a 2600.

I ma off to a rolling road next with the 2600 to find out what the power delivery actually is
 

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Discussion Starter #43
If you look at the opening for the incoming unfiltered air, it is, imho, way to small to support any sizable volume of airflow. The opening's area is no where near the area of the bellows end opening.
Now that you mention it those openings on the side of the filter canister do look too small and restrictive. (The photo does not show the larger opening)



Mark
 

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Discussion Starter #44 (Edited)
I think Dan hit the nail on the head! After taking some measurements and doing a few quick calculations, the surface area of the intake opening on the air filter canister (2.25 x 1.00) has approximately 2.25 square inches of surface area (discounting several ~1/4" holes around the 'snail shell shaped' spiral intake) . The air plenum intake (3-1/16" in diameter) has approximately 7.7 square inches of surface area. Gee, why would that be; a self induced restriction, a miscalculation? If each carburetor throat is roughly 40 mm in diameter or 32 mm venturis (is that right for a 40DCOE or 44 mm for a PHH44?) how large should the intake be? I have not had any fluid dynamics classes lately but the car runs better with more air. Perhaps I'll put the "air canister" back together without the filter to eliminate the filter as a possible source of the restriction.

The way the filter canister is designed the air comes in the outside of the canister, through the filter, which is sealed top and bottom, into the intake plenum and through the carburetors. I can envision the air filter canister drilled on the back side, with a hole saw, to resemble Swiss cheese. Furthermore, I wonder if the stock PHH44's would not benefit from a few extra cubic feet of air; if the filter is not the problem!

I remember the interesting thread about the Two-Liter Sprint daily driver. It looks so good you'd think it was a trailer queen. That article prompted me to order the Pertronics units that are somewhere in the garage. I guess that I missed the 36 mm choke description but I will not argue as Tom Sanor told me the 2600 factory Weber cars came with 36 mm chokes and 45 DCOE's although he set his 2.6 Sprint up with 40DCOE's and 28 mm chokes and said it ran great. He figured the factory 36 mm chokes were for race cars that did not need low end torque for stop and go driving.

Mark
 

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I need to check some things.

I seem to recall the main air inlet source being a large gap in the bottom between the plate and canister, not the tiny holes up higher. Maybe you have the wrong element?
 

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Or, maybe I remember my 14 year old girlfriend's phone number better than the design of an Alfa canister?
 

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She was 14. So was I. 1965
 

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More on chokes

Your comments

" I guess that I missed the 36 mm choke description but I will not argue as Tom Sanor told me the 2600 factory Weber cars came with 36 mm chokes and 45 DCOE's although he set his 2.6 Sprint up with 40DCOE's and 28 mm chokes and said it ran great. He figured the factory 36 mm chokes were for race cars that did not need low end torque for stop and go driving.
"

Are all absolutely correct but I seem to be unable to go down the road of smaller chokes for more bottom end torque/power on dellortos. All the Weber development posts on the 2600 alfabb suggets a move to 30mm or 28mm chokes to remove a large flat spot on acceleration , I will start a seperate thread on this as it has little to do with this thread "two litre down on power"
 

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Discussion Starter #50
Like most, this thread is starting to degrade...perhaps I should have titled it "What is choking my Touring Roadster beside the choke!

Don the air intake has an opening on one end of the snail shell shaped rib around the center of the canister. It is ~2.25" X 1" but not shown in my photo above.

Mark
 

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This is an interesting topic. I have been contemplating choke size for my yet-to-be-built 102 engine. Most of the literature that I have come across seems to indicate something in the range of 30 or 32 for a mild 2 liter. The guy that designed my pistons and connecting rods said 30 would be plenty. More evidence; if one averages the choke sizes (by area) for the old Solex 44s, the number 30 comes up again. The 102 engine seems to be more of a stump-puller than a Formula-1 contender, so bigger might not be better in this case if you want to keep the low RPM grunt. I would think that after the 50+ years these cars have been around, someone would have come up with a tried and true recipe.

Regarding the air filter box for this car, I too find the small inlet rather annoying. In my earlier days, I spent most of my automotive time with BMWs, for years driving a 2002 ti powered 1600. This engine had side draught Solex 40s, with independent throats like Webers rather than the two-stage 44s like on 102/106 (Choke size: 34, for anyone who might be wondering). It also had an inlet system similar to the 102, but had 2 filter elements at each end of the plenum, rather than one at the front. These filters were capped with inlet air being fed via a narrowing snorkel-pretty much the same situation as the 102. I "corrected the problem" by removing the end caps and retaining the filter elements by clamping them together to the plenum with a long section of all-thread. This did increase the air flow significantly, but the point I wanted to make here was that this also came with increased leanness. To compensate, I had to re-jet both the idle and main jets. Mains went from 130 to 145, if I remember correctly. I do not recall what I did with the idles. Replacement jets came from old Opels and the like that were well represented in self-serve wrecking yards at the time. I have no idea where to locate Solex jets today.

My plan with the future 102 engine is to make a modified air cleaner cap, the piece held on at the bottom with the wing nut, to keep things looking relatively original, apart from the upgrade to Webers. In theory, the cap would be as minimal as possible, basically covering the end of the element, with the rest , or much of it, open, which should allow for a reasonable air flow improvement. I didn't have an actual element originally, so I purchased a new one not too long ago from Classic Alfa that allegedly fit the 102 (UFI brand p/n 2708400). This turned out not to be the case, as the diameter was much too large, barely being able to stuff it in. After contacting Richard at Classic Alfa with this result, the air filter is no longer being offered there. But, other suppliers may still be selling these exact ones, so beware. Installing one in your car will result in some flow issues as very little air will get around the element.

Mark, from your photo, your element looks rather large. The inner diameter should be, apparently, around 3 inches. The one I have (pictured, from Classic Alfa) is about 3 1/2.
 

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Discussion Starter #52
The inner diameter of the air filter is about 3-1/2" and the outside diameter is about 4-1/2" it looked like a perfect fit.

I guess I tempted fate last night, taking the car out for a 'short' test ride, with the air filter removed but the rubber hose connecting the empty air filter housing to the air intake manifold. Again the car started and ran weakly down the street and back (0.2 miles). It stalled in the couldesac in front of my house and refused to restart. The rubber hose was removed, I even gave it a shot of starter fluid but it refused to start -so it spent the night covered, under the street light, protected by one of those little orange reflective triangles.

Mark
 

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Bummer!!! May I offer a suggestion.

Mark,
I wish we lived closer. Seattle is so far away from Georgia. I'd love to be there to celebrate with you if what I suggest suddenly solves your problem. Yes, there is something just not rightl But "fluid" mechanics misses the point. Webers work on speed of air passage. Air compresses and merely rushes faster through a smaller opening. Your latest experience says to forget the carburetors and air intake. If you stalled and couldn't get something moving even when you used starter fluid, then you have AN ELECTRICAL PROBLEM.

Experience is the best teacher. Long ago one of my two liter friends could not get his car to perform not long after I had just worked on his engine and it had run fine. He could not get his engine to run faster than 2500 rpm. Doesn't that sound like what you have been complaining about? He finally trucked it back to me to see if I could fix it. I tried everything. I couldn't get it to run any bit better. I fiddled with carburetors until I dreamed about them. Nothing I did made any difference.

Finally, after a week or so he happened to tell me about how he had put some wonderful new spark leads on his car so there would not be so much static on his radio. And I did a wonderfully smart and simple thing. I changed all his wonderful new spark leads back to a set of mine with solid copper wire. Then it ran super. Didn't you comment that you saw lots of sparks under the hood and changed your spark plug leads?

Seriously: Carbon track non static making spark leads do not work on two liter Alfa cars. They are NOT able to handle the high RPM involved. If you did switch leads, then try the old ones that used to work. I hope that finally solves your mysterious problem. I believe it will.

Or let me describe another vexing experience. I sold a 1750 spider to a young man who joyfully drove it home. Next day his father in great anger accompanied him when he brought it back, demanding a refund because it would barely run. I was amazed. It had run perfectly just the day before. I wondered what had been done to it. I was proudly told that the boy had even put in some new wonderful spark plugs. I said nothing, just puled out an old set of used ones I had not thrown out, put them in the car, and it ran perfectly. The boy and his dad said nothing, got back in the car and drove off. The wonderful new plugs were NOT in the proper heat range. If it is not the spark plug leads, then put in NGK BP7ES or Champion N9Y plugs. Some of those amazing new fangled plugs don't work as good as the old tried and true ones.

I was reminded recently that I should first try simple solutions when I face new problems. My mother turned 103 on the Fourth of July and I was home in Idaho. She asked me to fix the washer. It would not progress from wash to spin, etc. I suspected the teeny electric motor that moved the timer controls. In desperation I had to trace down a sawmill electrician on Saturday and found him getting his hair cut in the town barbershop. After he patiently proved to me the teeny electric motor that moved the timing mechanism was okay, he sized me up as "one of those guys who thinks it must be electrical when a bigger hammer doesn't fix things." He was right. I finally fixed the wash machine problem with a hammer and chisel. A metal disk was not supposed to be sliding back and forth on a shaft. Try the simple solutions first.

Jay
 
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