Weber with 34mm chokes - experiences? whodunnit?
Posted: Mon Dec 31, 2018 2:06 pm
Hi,
I have a question: “Who has (first hand) experience with a 34mm choke/venturi in his Paso 750 Weber?”.
After having read the Weber article on the 906 Weber from Higgy and Romus, I decided to switch the standard 36mm chokes/venturis for the 34mm versions after the complete rebuild/overhaul of my Weber.
At first I decided to use the standard jet settings for my baseline (57/150/170 idle-main-air) but after having read the various articles/manuals on the Weber I doubt this is the best way to proceed.
From what I’ve read the main jet should be roughly a 0.10mm smaller if the venturi is 2mm smaller, so instead of 150 size I should use a 140 size etc. (again to start with).
The air corrector on the other hand is much more of a mystery to me: I’ve read somewhere that normally the difference between the 2 is about 30 (but to be honest in all application tables for the DCNF I’ve seen so many derogations going from 125/220 to 135/170).
For the idle jet I think I will leave it standard (size 57) since I will buy sizes from 50 to 60 anyway since they are responsible for the sub 3000 rpm region.
Also I assume the change of choke/venture size has not a huge impact on the idle jet size.
So again, all considered I would love to know if someone has actually done this exercise and has any experiences with the jetting.
I struggle to decide if I should change the auxiliary venturis for the 4.5 versions (obtained) but due to lack of experience with the 34mm chokes/venturis, I think it’s better to first wait and see how it behaves with the 3.5 auxiliary venturis and try to optimize it without the 4.5 auxiliary venturis.
Playing with the pump jet cam is an exercise which will have to wait for later (I've bought a spare cam after reading Brutus's work on the Weber's cam profile), since otherwise I will loose track as result of all changes compared to the Original configuration.
Hope for some reactions/advise from you!
Frank
I have a question: “Who has (first hand) experience with a 34mm choke/venturi in his Paso 750 Weber?”.
After having read the Weber article on the 906 Weber from Higgy and Romus, I decided to switch the standard 36mm chokes/venturis for the 34mm versions after the complete rebuild/overhaul of my Weber.
At first I decided to use the standard jet settings for my baseline (57/150/170 idle-main-air) but after having read the various articles/manuals on the Weber I doubt this is the best way to proceed.
From what I’ve read the main jet should be roughly a 0.10mm smaller if the venturi is 2mm smaller, so instead of 150 size I should use a 140 size etc. (again to start with).
The air corrector on the other hand is much more of a mystery to me: I’ve read somewhere that normally the difference between the 2 is about 30 (but to be honest in all application tables for the DCNF I’ve seen so many derogations going from 125/220 to 135/170).
For the idle jet I think I will leave it standard (size 57) since I will buy sizes from 50 to 60 anyway since they are responsible for the sub 3000 rpm region.
Also I assume the change of choke/venture size has not a huge impact on the idle jet size.
So again, all considered I would love to know if someone has actually done this exercise and has any experiences with the jetting.
I struggle to decide if I should change the auxiliary venturis for the 4.5 versions (obtained) but due to lack of experience with the 34mm chokes/venturis, I think it’s better to first wait and see how it behaves with the 3.5 auxiliary venturis and try to optimize it without the 4.5 auxiliary venturis.
Playing with the pump jet cam is an exercise which will have to wait for later (I've bought a spare cam after reading Brutus's work on the Weber's cam profile), since otherwise I will loose track as result of all changes compared to the Original configuration.
Hope for some reactions/advise from you!
Frank