Alfa Romeo Forums banner

1 - 12 of 12 Posts

·
Registered
Joined
·
2,610 Posts
Discussion Starter #1 (Edited)
Hi All,

I have for sale :

2X desiamised inlet alucast

for alfa 2000 touring /sprint 102 serie

does also fit 1900 engine




channels bored ,alu tubes welded in ,front/rear machined

for conversion to 40 ,45 weber dcoe and 40 ,45 dellorto dhla carbs



for best performance I also advise to rework the inlet channels of the cilinderhead for a perfect air/gas flow and make a new gasket because "standard" gasket does not perfect fit

price eu 500,-


for info/shipping PM

rgds Franco
 

Attachments

·
Registered
Joined
·
2,610 Posts
Discussion Starter #2 (Edited)
alu adapter plates

Hi All,

I also have the alu adapter plates for mounting between carbs and airplenum


if you are going to use the original alu airplenum you need these 2 alu adapter plates , if you put K&N filters , horns or other on it you don't need these adapters


price for a set adapters is eu 130,-


rgds Franco
 

Attachments

·
Registered
Joined
·
2,610 Posts
Discussion Starter #3
Hi all

someone interested ?


desiamised inlet alucast

for alfa 2000 touring /sprint 102 serie

does also fit 1900 engine




channels bored ,alu tubes welded in ,front/rear machined

for conversion to 40 ,45 weber dcoe and 40 ,45 dellorto dhla carbs

and the alu adapter plates for mounting between carbs and airplenum these are also for 2600

rgds Franco
 

·
Push hard and live
Joined
·
10,453 Posts
Franco,

This appears in all regard to be nice work, and will allow the continued use of the standard inlet air plenum. I'm not sure it will allow use of the original support rod. Is the combination of the Weber + "gender mender" the same length as the standard PHH44? Either way, a modified support rod would not be a difficult item to fabricate.

Back when we attempted to convert 102's to Webers by just bolting them on to still-siamesed manifolds, we found stock Weber parts that allowed them to have their shafts connected in the middle as on a 105, even though the spacing is different. I don't know if those parts are still available, but it's a more elegant way to adjust the synchronization than using the two independent throttle activating rods. Both ways work, however.
 

·
Registered
Joined
·
126 Posts
Hi Franco, I'm interested.

But When I look at the modified ports on your manifold and compare it to mine, yours look much smaller. How will they mate up to the head. Are you modifying your head to mach that new size?

Bernoulli's "principle of fluids" would mean that the air/fuel charge would slow down suddenly when it enters the larger port on the head. This might not be a problem, I'm just not expert enough to say.

Here is a picture of my unaltered intake manifold ports vs the smaller ports on your manifold.
 

Attachments

·
Registered
Joined
·
2,610 Posts
Discussion Starter #7
weber inlet

Hi All,

for best performance I also advise to rework the inlet channels of the cilinderhead for a perfect air/gas flow and make a new gasket because "standard" gasket does not perfect fit


it is also possible to modify the bored alu tube channels of the inlet at the cilinderhead side for a better fit to the cilinderhead

for a perfect air flow

see picture , I did for my 102 spider and needed 4 x 2 hours grinding......



rgds Franco
 

Attachments

·
Registered
Joined
·
1,484 Posts
I prefer using plates instead of tubes

I also experimented for twenty or thirty years on trying to make a good desiamesed intake manifold for my two liter spider -- 102/2000 -- engine. I felt cheated that my car did not perform like the first one I drove in Germany [the factory demonstrator with a sportiva engine that my fellow ski patrol buddy brought back to Bergtesgarten on a three day pass to Milan] I wanted Webers. Still, there seemed no benefit with merely putting them on instead of solex carbs. I realized the intake for a Solex was siamised and the Webers actually had need for individual throats. So in my first attempt to desiamise I welded up and ground out. The throats ended up much too small. The second time I used tubes, and ended reading up on the theory of weber carburetors as "speed of air flow" in comparison to the theory of solex's "wet plenum". I realized that with a "tubed" intake manifold the holes were too uniform and larger than the 32mm (or was it 36) chokes in the webers [maximum size on 40 DCOE but available also on 45 DCOE]. The result was momentary stagnation of air and precipitation of raw gas to run back out and drip on the rail edge under the out side of the webers. Consequently, I decided to slice into the bottom of the intake manifold at the exact spot where the siamese was occurring, and weld in a vertical plate, thus dividing the two throats exactly equal. I figured the bit of constriction and the flat side in the passageway through which the air would have to go would make it go faster and perhaps "roll" it a bit. That also allowed continued use of the water passages in the intake manifold and did not distort appearance either.

Then I wanted to somehow fit the outside of the webers to the cold air box so I developed what I call a "gender mender" [outside bolts on webers are exactly opposite those on solex]. The frustrating error [yes a big mistake] then was discovered when I also "plumbed" the smaller top hole of the weber carburetor [the one to the top side of the floats] into the cold air box. Somehow that old Bernoulli guy was right again because that error allowed the passage of the air across the open end of that small hole to drop the pressure a bit on top of floats. That caused too large a spurt of gas to initially flow upon acceleration. I finally had to resort to the same solution Alfa used on the Sportiva engine [which was developed out of 1900 like the 102/2000] by installing an air line run from that small hole to point directly into the stream of air coming into the cold air box. Alfa did that too for the weber system when used on the 106/2600 engine, but had to run hoses to the "crossover" and point the ends to the entrance from the air cleaner to get a direct flow. Then with the momentary added pressure on the floats I no longer had to lift my foot off the gas to keep the engine from momentarily flooding when I accelerated. Once I understood the problem, I decided to try leaving out the plumbing to the top of the floats and merely using a screen on the hole to the outside of passage to the floats. With the floats exposed to "ambient" air, it doesn't have the momentary stutter and stall problem. It all makes sense now. For those of you who recall how the 1300 and 1600 veloce webered engines had the crossover to the cold air box, realize that the air came directly through that to a collector location between the carburetors [which was the location for the lines running to the top of the floats] and then the air turned to go into the intake ports on either carburetor. But the 102/2000 and the 106/2600 engines have intake manifolds that feed from one or other end instead of from the center. It is enough to merely fit a small sink washer spout screen into the small hole of the "gender mender" and do nothing more but leave the hole open to ambient air. But I must admit there is a downside [yes, the tubes as found on the sportiva have advantages] in that air boxes avoid the consequent carburetor sucking noise, although with the screens that is not as bad as merely using air horns.
 

·
Registered
Joined
·
126 Posts
I also experimented for twenty or thirty years on trying to make a good desiamesed intake manifold for my two liter spider -- 102/2000 -- engine.
Wow Jay, thanks, great information! You really went through a lot of work to get it right. Are you happy now? Does it feel more like that first car you drove in Germany?

Also, did you end up with 40 DCOE with 32mm chokes? I'd love to see a picture of your engine bay.
 

·
Push hard and live
Joined
·
10,453 Posts
Carmonkey,

There is more than one way to skin this cat. Jay's approach retains most of the original look, and certainly allows the Webers to work in the way they were intended. I may have some different views on the science of his explanations, but it does lead one to understand why the plate method works where the siamesed intake runners will not.

I wasn't aware that Jay had tried the welded-tube approach, with unsatisfactory results. I would have thought that could be made to work, but it may be that the diameter(s) were problematic.

To take it a step further, however....

Some of the early 1900 and 2000 engines were used in performance applications, and these often had an intake manifold developed, I think, by Conrero. If you saw one you would immediately see the resemblance to modern 105-style Weber manifolds. They have one intake runner per cylinder, with no connection between the runners, and no heat provided by water circulation as with the Solex manifold. The heat is necessary to help the air-fuel mixture turn all those corners, but reduces the horsepower a little as heated air is less dense than cool air.

The welded plate approach still leaves four fairly crooked intake tracts, simply sealing the original connection point between them. The original tracts look somewhat like this )(, with the close points opened up to connect them. Straight tracts, in theory, should flow a bit more air, although it may be only a slight bit more.

The Brazilian version of the 2000 was made by FNM, and was progressively increased to 2150 then 2300 cc's, The 2300 version uses a Weber-style intake supposedly modeled on the Conrero, originally with Solex 40ADDH carburetors. Essentially clones of the Weber 40DCOE. The 2300cc engine is rated at 149HP vs the Italian 2000 being 120. As the cam profile is the same, we must think that the combination of 15% more CCs and better breathing is what produced a 29% increase in power.

Anyway...

You can buy a modernized copy of the Conrero/FNM 2300 manifold that uses standard 105-style rubber isolator blocks (this is a big cost savings) from OKP.

This approach increases the angle of the carbs, which is good in that it eliminates the fuel rejection generally observed on both the original Solex carbs as well as Webers mounted onto a Solex manifold.

However, the angle prevents use of the original air plenum or carb support rod. You can use something like K&N filters, and fabricating a rod and carb-securing plate is not all that hard. You must also organize a different cable linkage. I used a standard kit from Webcon that solved that issue neatly.

I am hoping my nearby neighbor JP gets his 2600 finished soon so we can drag race through Washoe Valley to compare the two cars.

Here's a quick pic of a 102-2000 I'm finishing now, using an FNM manifold and 40DCOE2's rebuilt for me by Gordon. I have yet to get the carb-bracing plate, or make the support rod. The FNM manifold uses unique rubber isolator blocks different from all others. PITA.
 

Attachments

·
Registered
Joined
·
1,484 Posts
How big are the holes?

Franco,
I sleeved one, and had problems because I made the holes 45 mm all the way through. That gave poor idling and starting, but with 45 DCOE 27's a pretty good top end. When I tried welding up and routering I could only get a 26 mm ball through. Never could get the engine really screaming. I decided on plates to as easiest manner to have individual runners bigger than welding and router but not as big as a straight pipe through. Webers work on a "puff of air" theory and the speed through the intake is what keeps the gasoline droplets suspended.

So, maybe your intake has possibilities. (a) what is the diameter of the holes in yours? , and (2) how many Rasbucknicks? Jay
 
1 - 12 of 12 Posts
Top