**Caution I have no experience tuning Solex carbs nor do I have a
running Solex engine at this time**
Ken,
Your question is of interest to me since I just obtained a restorable 68
2000 with a spare Solex engine. Since I have not seen a response, I
thought I would add some information to a least fan the flames ;)
Solex carbs appear to use the same jet size designation as Webers, the
jet number refer to the jet hole diameter. For example Jet number 160
has a 1.60 mm diameter hole. In general terms for gas jets the higher
number is richer, for air jets the higher number is leaner.
ken pletcher wrote:
> ...
> Second question is about solex jets.
> for idle is the higher number richer or leaner<
I'm unsure here since the idle (pilot) jet meters gas and air -- the
number appears to refer to the gas jet diameter so a larger number would
be richer. Mine are #55 (.55mm) and the holes in the side and top (air
bleed) are >.55mm (~1mm). Note the pilot jet also meter fuel for
mid-range response (transistion from idle to main jets), if the car
stumbles off idle one might go to larger pilot jet for mid-range
enrichment and use the idle mixture screw to lean out the idle if
necessary. However, the emulsion tubes also affect mid-range so a change
may be in order there as well. BTW, Weber uses a combined designation
for idle jets like 55F9, where 55 refers to the gas jet diameter and F9
is an air bleed code that defies logic (from rich to lean:
F6,F12,F9,F8,F11,F14,F13,F2,F4,F5,F7,F1,F3).
> for main fuel is the higher number richer or leaner<
The main fuel jet is in the bottom of the fuel block and the larger
number is richer. This appears to be confirmed in the Factory parts
listing:
Part# Part Name
16033-25520 Jet-Main #160 -- stock jet size?
16034-25520 Jet-Main #155 (1000M) -- leaner jet for high altitude
(~3200ft)?
16034-25521 Jet-Main #150 (2000M to 3000M) -- leaner for higher
altitude (~6500-9750ft)?
16033-25522 Jet-Main #145 (4000M) -- leaner for runs up Mt Fuji
(~13000ft)?
> for main air is the higher number richer or leaner<
Using the logic above and the Weber convention the higher numbers are
leaner. According to A. Graham Bell's book "Four-stroke Performance
Tuning" (refering to Webers) a larger air bleed leans the mixture more
at high rpm than at lower rpm. A change in main fuel jet size affects
the mixture strength uniformly at both high and low rpm (remember you
need to be near WOT to get the main jets going at low rpm). BTW, Bell's
book (ISBN 1859604358) is an excellent source that covers a wide range
of engine mods for performance tuning. Bell resides in Maitland, New
South Wales -- any of Australian Sports owners heard of him?
I disassembled one of my Solexes and noted all the jet sizes; they
appear to be different from stock. Can anyone confirm the best jets for
street? These carbs were on a U20 with a Solex ("B") cam and 1.5" OD
header (I assume stock pistons and compression ratio -- but I haven't
pulled the head to confirm). Here is a jet listing with the Factory
Manual and Parts list for reference:
Jet My # Shop Manual # Parts List #
---- ----- ----------- -----------
Main Gas #135 #180 #160
Main Air #140 not listed not defined
Pilot (idle) #55 #60 #60 (#55 optional)
Starter #160 not listed not defined
Accel pump #35 .3mm (#30?) not defined
Fuel Block #8 not listed not defined
Emulsion tube #M not listed not defined
(inside fuel block)
Also my carbs have 34mm chokes (venturis) where the shop manual lists
37mm as standard. 34mm seems better suited for the street (this is what
Bell recommends for a 4 cylinder with 500cc per cylinder) and may
explain the leaner jet selection on my carbs. I wish I had these install
and running on my car to verify the performance -- I hope to prior to
Shasta.
Does anyone have a list (and source)of Solex jets available.
If you have read this far, thanks for your time -- I hope someone holds
the decoder ring.
Todd Osborn
68 2000 DATSFUN (SU, B cam, Comp springs...)
68 2000 Solex (low chassis# but in many pieces)
San Jose, CA
|