[alfaparticle]

You usually have to increase the main jet by 5 when you go up 2 mm in venturi size. Nothing else is likely to change. If you see an improvement it is likely to be at higher rpm.

 

[gigem75]

Thanks, I put in 135's over the 130's they came with a couple of days ago. I have 140 & 145's if I need them. This is a new set up so I'm slowly feeling my way around. I'm sitting on my dyno so it may not be the most emprical method out there. I do have larger intake valves and opened seats along with the cams I'm hoping the 32's will help all that work together. Since there is no increase in displacement all I can do is hopefully increase the volumetric effencicy.

 

[flivesay]

I'm sitting on my dyno so it may not be the most empirical method out there.

maybe not empirical, but the best for the guy sitting in the driver's seat

 

[alfaparticle]

32's are not too big - they were standard on 1750's with mild cams.

 

[gigem75]

I suppose I'll have to push it to the limit.

 

[gprocket]

Hey Gig, Are yours 40's or 45's? Can you run down your motor specs - sounds like I'm building a clone of what you're doing ( with 45/151s). I know so little about carbs so this is a really helpful thread.

 

[gigem75]

No sweat, 12mm intake 11mm ex cams, hd valve springs, head, intake ported to JimK specs, big intake valves, seats opened 50 thou, gta style headers, motronic pistons, rml distributor, msd6al. And the new 40 dcoe 151's. These are new to me on this car as I had been running a HP pump but I was experiencing detonation at 4000 due to a lean flat spot I couldn't tune out without having it way to rich everywhere else. I'll hopefully figure that out but it will be with my spare motor on the test stand I built. I wouldn't necessarily call it a race motor but a healthy quick street motor. How is yours working for you?

 

[alfaparticle]

Some people have had problems with 45 151's that were fixed by drilling an extra progression hole. Richard Jemison is one person who has done it.

 

[hunttheshunt]

Some people have had problems with 45 151's that were fixed by drilling an extra progression hole. Richard Jemison is one person who has done it.

Are you sure you don't mean 45DCOE152 ? They often need for some applications an extra progression hole drilled - while the 152G already has it from the box. 40DCOE151 & 45DCOE152(G) are what they call "Spanish aftermarket carbs".

 

[alfaparticle]

Are you sure you don't mean 45DCOE152

That may well be the case.

 

[gigem75]

"They", that's a good one I've had both and would be hardpressed to tell the difference. Both are "aftermarket".

 

[gigem75]

I did notice some 4k+ increase with the 32 chokes but just as enlightening was the wide band going from 11 to 12.5 and a readjustment of the idle screws. Bottom end didn't seem to suffer. I haven't looked yet but I suspect the plugs will look lighter (better as they were a little dark) causing me to stick with the 135 mains for now. Driveability still great no bumps, spits, or stumbles.

 

[Alfar7]

Progression holes

Here`s a thread on the subject:
http://www.alfabb.com/bb/forums/cah...-air-intake/32856-weber-dcoe45-152-45dcoe-progression-circuit-modification.html

 

[gigem75]

Page not found?

 

[Brandman]

I found the Weber ID for the two different pump jets.
76801. (classic)
76818. (emission)
But i guess the short version (76818) is a special design just for Alfa romeo.
(a dealer in UK called them also "Alfa type")
In the exploded view for the 40 DCOE 120/121 you can see the same pump circuit system (no back bleed) but the pump jet ist the long one (76801).
I am not sure, but i think the 40DCOE120/121 are never used in Alfas.
In my opinion the long version should also work in an emission carb.
For what Alfa needed the short one ? I don´t know.
So i´ll try the long ones, size 0.30.

 

[Alfar7]

Thread on Progression holes

Again...corrected

http://www.alfabb.com/bb/forums/car...-air-intake/32856-weber-dcoe45-152-45dcoe-progression-circuit-modification.html

 

[alfaparticle]

40DCOE 120/121 were fitted to Simca 1000 Rallye 3 according to http://gazoline.net/forum/technique...ion_des_carburateurs_par_Constructeurs_et_modeles_de_RENAULT_a_fin_de_liste.pdf

This list also shows other emissions Weber applications.

 

[papajam]

I am not sure, but i think the 40DCOE120/121 are never used in Alfas.

Correct. The 120/121 were never factory fitted to an Alfa The closest (suffix number wise) were the 124/125 on the Alfetta GTV 2000 (engine type 01655).

 

[gigem75]

Wow, Simca, haven't heard that since high school, reminds me of old friends, Saturday tuning for Sunday, our group had the MG's, TR's, VW's, and there might even have been a Simca in there somewhere. Thanks

 

[Alfar7]

Link

This is the 3rd time I have posted it. The link is two lines long and the BB software is changing it when hitting reply....

http://www.alfabb.com/bb/forums/car...-air-intake/32856-weber-dcoe45-152-45dcoe-progression-circuit-modification.html

Did it again! ***!

Search the BB for Weber DCOE 152 progression curcuit modifications.