[383494]

I have searched the threads with no real conclusions so in a sense I am calling for a fresh, clear discussion on Webers, old and new regarding streetabilty, reliability and suggestions. In my eyes dual 40 DCOE or smaller makes more sense for the street and tuning of a relatively mild motor. Yes dual Webers are sexy as hell but do they work well for street/hot street?

CFM required for a 1600 to 5500-6000 rpm is 140. Seems to me that this is a tough match.

I am here to learn, so please constructive comments please. I have the dual manifold and am very curious to everyone's input.

Cheers, S

 

[Gordon Raymond]

Yes, 2 40DCOE's are fine for 1600's. Choke range for stock street is 27 to 30 mm. Generally non-emission Webers are easier to work with than 40DCOE151 type or other emission. Whichever, both must be the SAME. (ie, both 40DCOE2's) and of the same build period.
For hot street, seriously modified engines, choke size for 40's can go up to about 35mm, or with 45DCOE's to 36mm or so, depending on cams, compression, gearing and more. Generally for street application, 40's will offer better low end torque, 45's better high rpm Hp.
This is a pure race 1600 I use on the street.

It runs custom cut 35.7mm primary chokes in 40DCOE2 Webers. 10.7 /11:1 compression, custom RJR Richard Jemison cams 10.55 lift.

 

[383494]

Yes, 2 40DCOE's are fine for 1600's. Choke range for stock street is 27 to 30 mm. Generally non-emission Webers are easier to work with than 40DCOE151 type or other emission. Whichever, both must be the SAME. (ie, both 40DCOE2's) and of the same build period.
For hot street, seriously modified engines, choke size for 40's can go up to about 35mm, or with 45DCOE's to 36mm or so, depending on cams, compression, gearing and more. Generally for street application, 40's will offer better low end torque, 45's better high rpm Hp.
This is a pure race 1600 I use on the street.

View attachment 1666372
It runs custom cut 35.7mm primary chokes in 40DCOE2 Webers. 10.7 /11:1 compression, custom RJR Richard Jemison cams 10.55 lift.

Sweet! I am a bit detail oriented on actual vacuum signal on the venturis and this has served me well. Torque/HP balance is essential, and I love the high rev capability of the Alfa Bialbero if it bogs on launch what's the point? Thanks Gordon!

I am also a little OCD on tuning intake and exhaust length/velocity...for another time.

Cheers, S

 

[Gordon Raymond]

Most we set up on either engine or chassis dyno for >close< to actual set up, regardless if a street or track engine. EACH set up is build specific, and initial set-up a general base line to get it running. Final / final set-up is only minor corrections, street or track.
This IS the only way to get it right that works 100% of the time.

 

[383494]

This is a GREAT post! Nice find Samakijoe!

All you wanted to know about DCOE carbs and were afraid...

 

[PSk]

Yes dual Webers are sexy as hell but do they work well for street/hot street?

I'm confused. Alfa Romeo, and other manufacturers, produced hundreds of thousands of road cars with this set up. Of course they work well for street work.

Pete

 

[383494]

I'm confused. Alfa Romeo, and other manufacturers, produced hundreds of thousands of road cars with this set up. Of course they work well for street work.

Pete

Well, regardless of the success of the setup, I am always inquiring to learn as many others I am sure to have conversations about HOW to achieve success as we now have to scrape and search for functional units whether Italian originals or modern knock-offs. These are not exactly dead easy carburetion configurations for the average and even above average wrencher. I always respect your input PSk, please respect mine.

We should always show respect and encourage the spectrum of knowledge that is potentially available from members. My number one reason for abandoning a forum is when knowledge and education are blocked. So far so good on AlfaBB.

Again I refer to this excellent post a day after mine:

All you wanted to know about DCOE carbs and were afraid...

S

 

[PSk]

My recommendation is to set them up exactly as Alfa Romeo did. A great starting point 🙂, and at least for 70s Alfas they work very well.

But yes your post makes sense if you want to modify the tuning. I just did't understand your question on them being streetable, apologies I've driven carbs for years.

Pete

 

[383494]

My recommendation is to set them up exactly as Alfa Romeo did. A great starting point 🙂, and at least for 70s Alfas they work very well.

But yes your post makes sense if you want to modify the tuning. I just did't understand your question on them being streetable, apologies I've driven carbs for years.

Pete

I have driven carbs for 40 odd years. Recently I rebuilt my '51 Ford Flathead Holley 94. This may sound straightforward but I found the jetting and other minor tweaks were necessary to successfully get this iconic American 2 barrel carburetor to provide the driveability I needed. This is an approximately 3900CC (239 CID) V-8 and the Holley 94 provides about 200 cfm. While flathead v8 enthusiasts constantly (as well as others) overcarb this is an extremely important issue...for a useful streetable motor this is an important factor. If I were (which I will not) to add a second 200 cfm Holley/Stromberg whatever to my old Flathead, I would blank, as in a solid plate ,fake carb to keep this motor running practically on the street.

So, what does this mean for the Alfa owner? Or anyone else trying to achieve performance regardless of application? Learn from those who are the experienced and willing to share their wisdom.

S

 

[PSk]

Remember these Alfas are a carb per cylinder so very different to your very cool flathead

Pete

 

[alfaparticle]

Alfa and Weber worked together to get the best settings for the production cars. Nobody on here has resources that approach theirs. However if you live in an unusually cold or hot climate or at significant elevation above sea level then your car may run better with some minor jet changes. But if you install aftermarket cams, exhaust systems, intake systems then tuning using a wideband AFR instrument to tune the carbs is essential to get the best results from your modifications. There is a wealth of knowledge and experience that has been posted about this on the ABB which is easily found with the search function.

 

[DPeterson3]

I’m going to try to make this short. I’ll probably fail.

One of the things I’ve never read in any book is a discussion of why Alfa, and maybe others, plumbed their float bowl vents to various locations in the inlet tract. With the 60’s 105’s the air inlet for these was displaced to where the intake tube coming across the engine dumps downward into the plenum. The 2600 with Webers had three separate lines snake all the way around to a point on the cross tube over the top of the engine.

With the work being done by Keith Franck, I’ve come to believe that Alfa would start with an OK jetting, then locate a spot where either pressure, or vacuum, or a standing wave could be used to massage the E-tube transfer curve in a way that smoothed the transition from idle to main circuit. My 65 Sprint GT had zero bad behaviors and returned pretty good mileage. It’s common that we’ll set up our idle jets too rich, or have our mains come in too soon, to avoid the transition “bog”. I believe the displaced bowl vent system was a way to get the mains to come on sooner without making either circuit too rich.

I doubt any one of us have done a Weber conversion, then drilled 50 holes along our intake tract in order to perform 50 dyno runs looking for the magic spot.

Somewhere, that knowledge/art was documented.

 

[383494]

I’m going to try to make this short. I’ll probably fail.

One of the things I’ve never read in any book is a discussion of why Alfa, and maybe others, plumbed their float bowl vents to various locations in the inlet tract. With the 60’s 105’s the air inlet for these was displaced to where the intake tube coming across the engine dumps downward into the plenum. The 2600 with Webers had three separate lines snake all the way around to a point on the cross tube over the top of the engine.

With the work being done by Keith Franck, I’ve come to believe that Alfa would start with an OK jetting, then locate a spot where either pressure, or vacuum, or a standing wave could be used to massage the E-tube transfer curve in a way that smoothed the transition from idle to main circuit. My 65 Sprint GT had zero bad behaviors and returned pretty good mileage. It’s common that we’ll set up our idle jets too rich, or have our mains come in too soon, to avoid the transition “bog”. I believe the displaced bowl vent system was a way to get the mains to come on sooner without making either circuit too rich.

I doubt any one of us have done a Weber conversion, then drilled 50 holes along our intake tract in order to perform 50 dyno runs looking for the magic spot.

Somewhere, that knowledge/art was documented.

This is helpful. I am already losing interest in this site as I paid for premium membership. No big deal 20 bucks. My hope was for fresh, new perspectives including mine would be encouraged. So called self-anointed experts pontificating that I just use the search function is a clear signal of stagnation and smug mentality that the community has it all figured out. I do not doubt and in fact have received very good information has been provided that is indeed worth more than 20 bucks. Thank you DPeterson3. I seek education, and already I am finding that in fact there are other sources providing more engaging content.

Properly setting up carbs is something I have known all my life, growing up in a good old fashioned junkyard my Father (RIP) started and we encountered all sorts of carb challenges going back to cars from 1910's onwards. FordBarn is an incredible forum, an example to all. This knowledge is dying, I intend to do my part to preserve and advance that old valuable wisdom , as I do for all my projects forward to the next generations. I am encouraged by every positive constructive post I find or is responding to mine. So thanks.

Shout out to Jim Steck, Paul Spruell, and all the positive posts and private conversations I have received, otherwise I "change the channel, fellas".

Perhaps this may not be the place for me, nor anyone else looking for pure sharing of experience or knowledge. A pity.

Best Regards, S

 

[alfaparticle]

None of the members who took time to respond to your questions are "self appointed experts". Any advice that I give is on a take it or leave it basis. You will continue to be frustrated when you ask questions and then challenge the answers that you receive. Some of us who have posted detailed specific advice advice don't feel like repeating it over and over again to members who are reluctant to use the search function.

 

[PSk]

I'm not sure what you are after, and I assume if I can't work it out, unfortunately others probably cannot either.

If you are modifying your engine, then I suggest you post your specs, such as camshafts, compression ratio, etc., and many people will be able to offer their advice as many Alfisti do enjoy modifying and extracting more power from their engines, and want it to work for the road well also. And yes as Ed says, the search function is really useful because the same questions have been probably asked and solved before.

If not modifying, as I have already recommended, use Alfa tuning specs and go from there
Pete

 

[DPeterson3]

This is helpful. I am already losing interest in this site as I paid for premium membership. No big deal 20 bucks. My hope was for fresh, new perspectives including mine would be encouraged. So called self-anointed experts pontificating that I just use the search function is a clear signal of stagnation and smug mentality that the community has it all figured out. I do not doubt and in fact have received very good information has been provided that is indeed worth more than 20 bucks. Thank you DPeterson3. I seek education, and already I am finding that in fact there are other sources providing more engaging content.

Properly setting up carbs is something I have known all my life, growing up in a good old fashioned junkyard my Father (RIP) started and we encountered all sorts of carb challenges going back to cars from 1910's onwards. FordBarn is an incredible forum, an example to all. This knowledge is dying, I intend to do my part to preserve and advance that old valuable wisdom , as I do for all my projects forward to the next generations. I am encouraged by every positive constructive post I find or is responding to mine. So thanks.

Shout out to Jim Steck, Paul Spruell, and all the positive posts and private conversations I have received, otherwise I "change the channel, fellas".

Perhaps this may not be the place for me, nor anyone else looking for pure sharing of experience or knowledge. A pity.

Best Regards, S

After reading your reply, I can’t tell if your “thanks” to me was sincere or sarcastic. Interesting.

My larger point was to help you identify the fork in the road. If you have a stock 1600, and are considering shifting from an OE downdraft 2-bbl to a pair of Webers, your best bet is to exactly duplicate the factory set up. It will address the possibly undocumented tuning hurdles. If you want to add Webers to a highly modified engine, then you might reach out to some people that have faced those hurdles.

As I noted, the factory setup delivers an entirely satisfactory drive.

 

[Gordon Raymond]

Both for street modification or all out track competition, there are those here that have addressed these issues with undeniable accuracy. Have you?

 

[383494]

After reading your reply, I can’t tell if your “thanks” to me was sincere or sarcastic. Interesting.

My larger point was to help you identify the fork in the road. If you have a stock 1600, and are considering shifting from an OE downdraft 2-bbl to a pair of Webers, your best bet is to exactly duplicate the factory set up. It will address the possibly undocumented tuning hurdles. If you want to add Webers to a highly modified engine, then you might reach out to some people that have faced those hurdles.

As I noted, the factory setup delivers an entirely satisfactory drive.

DPeterson3, my thanks were sincere, no confusion intended. And again thanks, as a forum is a forum, and should initiate conversation. I appreciate both your responses. Some others here have been not been so considerate, the reason I vented off steam.

Cheers, and all the best,

 

[383494]

Both for street modification or all out track competition, there are those here that have addressed these issues with undeniable accuracy. Have you?

And Gordon nails the forum bully persona. Say "good-riddance" to me if you like but this is something else. I thank those who have provided me their time and patient advice.

Otherwise the worst snob moderators in any forum I have belonged to. Cancelled my premium membership. And thanks Gordon, for clarifying I am in the wrong place.

Ciao

 

[65Sprint]

Wow. Right, Gordon, "the forum bully persona". You ought to read his posts when he's "really mean". Thanks, Miller91, needed some Monday morning humor. Cheers and all the best.