Rich running Webers
- Thread starter Brian
- Start date
decoupe
(deceased)
Brian:
My 73CS is not stock and is running 38/38 DHAS downdrafts (dual), 282 cam and a bunch of other stuff and I'm running "50" jets. I know that this is a very different carb but my guess is you are still to big on the primary jetting. Also be sure of the pressure on the fuel delivery is around 3.0 psi.
I attached the Lean Best Idle link for progressive carbs in case you haven't seen it. This was critical for dialing in mine at 4000' versus the sea level tuning that it had when I bought it.
Good luck.
Doug
http://www.redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm
My 73CS is not stock and is running 38/38 DHAS downdrafts (dual), 282 cam and a bunch of other stuff and I'm running "50" jets. I know that this is a very different carb but my guess is you are still to big on the primary jetting. Also be sure of the pressure on the fuel delivery is around 3.0 psi.
I attached the Lean Best Idle link for progressive carbs in case you haven't seen it. This was critical for dialing in mine at 4000' versus the sea level tuning that it had when I bought it.
Good luck.
Doug
http://www.redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm
Honolulu
Well-Known Member
jets jets jets
Here's what I have gleaned from other lists over the years. YMMV. And I will say that I still run my Zeniths. Do what you like, it's your car, but at idle the carb should be feed gas through the idle jets only. Thus, main jet size is usually unimportant at idle; but float level setting can be influential.
32/36: f7 emulsion tubes, 140 to 145 primary jets, 185 air correctors, 50
accel. jet, 4.5 venturis if you need parts, call autobahn at 310-821-5050
32/36: The primary venturi is only 26mm, whereas the minimum recommended by Weber would be 28mm. However, you can make them work OK with 140-145 main jets and 160/170 air correctors. The 3.0 litre and the 2002 engine have the same size cylinders, so you can use the 2002 jetting.
3.0 liter M30 (9:1) Weber 32/36 jet settings: Primary air correctors = 170 and 140 mains, secondary air correctors 160 and 140 mains.
3.5 liter M30 (8:1, 3430cc): Primary air correctors 185, 145 mains, Secondary air correctors 190, 150 mains. This 3.5 jetting had previously produced a light-throttle stumble, but this is currently tweaked out with the idle mixture screw, and the motor pulls cleanly at all RPMs/ throttle positions. If it returns irrevocably, I will try slightly smaller primary air correctors.
Rule of thumb for jetting: Choose a main jet number four times the venturi diameter; e.g. a 30mm venturi equates to 120 main jet (=30*4) or 1.2. Then you can adjust the main jet size by increments of five, both smaller and lager..... 115, 125, 130, 135
For air-correction jets, larger jets means more air and larger main jet means more fuel. Start an air-correction jet with a value of 60 larger than the main jet, e.g., if using a 120 main install a 180 air-correction. Go for a drive and pay attention to 3k-5k RPM range, tailpipe and spark plug deposits. Use a smaller air-correction jet to establish a richer mixture or bigger air-correction jet for leaner mixture.
If the engine coughs and stumbles until it reaches 2k RPM, then you need to look at the idle jet.
38/38 DGAS is usually jetted for a 3 liter V6. idles .045 mains 142 airs 185. 142 mains, 45 idles, and 175/185 for air correctors, f50 for emulsion tube, 0.55 for the pump jet, 2.50 for needle valve, to richen the mix go up on the mains or lower on the air correctors.
Stock jetting for 38/38 is 145 mains 185 Air and 045 Idle jets according to the tech guy at www.redlineweber.com who was a great help to me.
Weber 38/38 Jets - My mechanic used a portable exhaust gas analyzer to re-jet: main 130, Idle: 60, Emulsion Tube: F57, Air Correction: 185, blocked the power valve, floats set to maximum (would need to dig out what level that is)
.
At cruise, the car is pretty much running on the idle jets, and you step on the gas a little and it almost transitions to the main jets and in the middle is some turbulence and stumble. Since the 38/38's are so big compared to the comparable flow of a 32/36 in this situation, you have some issues. Punch it and the car goes, but on smaller transitions in normal driving, the 38/38's don't work as well at 32/36's (or so some say), thought you get a lot more performance out of the 38s.
So we added a MSD ignitiion (6A) a month ago to get a hotter spark
(http://www.msdignition.com/ignition_4.htm) (also read Andrey Yurovsky's article at http://www.thedotcommune.com/msd_install.phtml). Now the car feels like it should...much smoother, idles better, hardly any stumble left, and a bit - not a lot, but a bit - more power. So after about 3 years, long talks with my local mechanic here in Dallas, reading stuff on the list, the coupe is finally running very nicely!
38/38's that are now on the 3.5L. Mains 135 Air 205 Idle 140. I am using the solenoid valves supplied by JAM (one on each carb) on the inboard set of venturis. For whatever reason the idle screws on the inboard vents seem to have more control of the idle than the outboards. I have tried running the outboard idle mix screws completely shut down but ran better turned out 1/2 to 1 turn. Am running the stock cam (whatever was on the 3.5) also running a 008 (last digits) distributor but running it w/o vacuum advance. Runs better that way.
Weber 40 DCOE Carb settings are: Choke 34, Main Jet 120, Air Correction 180, Emulsion Tube F11, Pump Jet 40, Idle Jet 55F8, Aux Venturi 4.5, Float Level 8mm
Alpina 45mm setup, thanks to a guy on this board (he has a '74 with Alpina stuff). I can't remember his name... it will come to me: Choke 34, Main Jet 120 Air Correction 180 Emulsion Tube F11 Pump Jet 40 Idle Jet 55F8 Aux Venturi 4.5 Float Level 8m
Here's what I have gleaned from other lists over the years. YMMV. And I will say that I still run my Zeniths. Do what you like, it's your car, but at idle the carb should be feed gas through the idle jets only. Thus, main jet size is usually unimportant at idle; but float level setting can be influential.
32/36: f7 emulsion tubes, 140 to 145 primary jets, 185 air correctors, 50
accel. jet, 4.5 venturis if you need parts, call autobahn at 310-821-5050
32/36: The primary venturi is only 26mm, whereas the minimum recommended by Weber would be 28mm. However, you can make them work OK with 140-145 main jets and 160/170 air correctors. The 3.0 litre and the 2002 engine have the same size cylinders, so you can use the 2002 jetting.
3.0 liter M30 (9:1) Weber 32/36 jet settings: Primary air correctors = 170 and 140 mains, secondary air correctors 160 and 140 mains.
3.5 liter M30 (8:1, 3430cc): Primary air correctors 185, 145 mains, Secondary air correctors 190, 150 mains. This 3.5 jetting had previously produced a light-throttle stumble, but this is currently tweaked out with the idle mixture screw, and the motor pulls cleanly at all RPMs/ throttle positions. If it returns irrevocably, I will try slightly smaller primary air correctors.
Rule of thumb for jetting: Choose a main jet number four times the venturi diameter; e.g. a 30mm venturi equates to 120 main jet (=30*4) or 1.2. Then you can adjust the main jet size by increments of five, both smaller and lager..... 115, 125, 130, 135
For air-correction jets, larger jets means more air and larger main jet means more fuel. Start an air-correction jet with a value of 60 larger than the main jet, e.g., if using a 120 main install a 180 air-correction. Go for a drive and pay attention to 3k-5k RPM range, tailpipe and spark plug deposits. Use a smaller air-correction jet to establish a richer mixture or bigger air-correction jet for leaner mixture.
If the engine coughs and stumbles until it reaches 2k RPM, then you need to look at the idle jet.
38/38 DGAS is usually jetted for a 3 liter V6. idles .045 mains 142 airs 185. 142 mains, 45 idles, and 175/185 for air correctors, f50 for emulsion tube, 0.55 for the pump jet, 2.50 for needle valve, to richen the mix go up on the mains or lower on the air correctors.
Stock jetting for 38/38 is 145 mains 185 Air and 045 Idle jets according to the tech guy at www.redlineweber.com who was a great help to me.
Weber 38/38 Jets - My mechanic used a portable exhaust gas analyzer to re-jet: main 130, Idle: 60, Emulsion Tube: F57, Air Correction: 185, blocked the power valve, floats set to maximum (would need to dig out what level that is)
.
At cruise, the car is pretty much running on the idle jets, and you step on the gas a little and it almost transitions to the main jets and in the middle is some turbulence and stumble. Since the 38/38's are so big compared to the comparable flow of a 32/36 in this situation, you have some issues. Punch it and the car goes, but on smaller transitions in normal driving, the 38/38's don't work as well at 32/36's (or so some say), thought you get a lot more performance out of the 38s.
So we added a MSD ignitiion (6A) a month ago to get a hotter spark
(http://www.msdignition.com/ignition_4.htm) (also read Andrey Yurovsky's article at http://www.thedotcommune.com/msd_install.phtml). Now the car feels like it should...much smoother, idles better, hardly any stumble left, and a bit - not a lot, but a bit - more power. So after about 3 years, long talks with my local mechanic here in Dallas, reading stuff on the list, the coupe is finally running very nicely!
38/38's that are now on the 3.5L. Mains 135 Air 205 Idle 140. I am using the solenoid valves supplied by JAM (one on each carb) on the inboard set of venturis. For whatever reason the idle screws on the inboard vents seem to have more control of the idle than the outboards. I have tried running the outboard idle mix screws completely shut down but ran better turned out 1/2 to 1 turn. Am running the stock cam (whatever was on the 3.5) also running a 008 (last digits) distributor but running it w/o vacuum advance. Runs better that way.
Weber 40 DCOE Carb settings are: Choke 34, Main Jet 120, Air Correction 180, Emulsion Tube F11, Pump Jet 40, Idle Jet 55F8, Aux Venturi 4.5, Float Level 8mm
Alpina 45mm setup, thanks to a guy on this board (he has a '74 with Alpina stuff). I can't remember his name... it will come to me: Choke 34, Main Jet 120 Air Correction 180 Emulsion Tube F11 Pump Jet 40 Idle Jet 55F8 Aux Venturi 4.5 Float Level 8m
decoupe
(deceased)
Jets jets jets
This is a great summary of everything Weber related. I'll hve to check against my set up but at 4000' it's bound to be a little different. I've gone through the Lean Best idle proceedurre and it runs well - no stumble but the gas analyzer sounds like my next adventure.
The link to dotcommune iisn't accessable but prehaps through Andrey's site...
Thanks
This is a great summary of everything Weber related. I'll hve to check against my set up but at 4000' it's bound to be a little different. I've gone through the Lean Best idle proceedurre and it runs well - no stumble but the gas analyzer sounds like my next adventure.
The link to dotcommune iisn't accessable but prehaps through Andrey's site...
Thanks
Honolulu
Well-Known Member
Looks to be in the second and third paragraphs.
Remember, this is all stuff I've collected over the years from the internet... and it just may be worth that.
Remember, this is all stuff I've collected over the years from the internet... and it just may be worth that.
Thanks for posting this stuff, everything on the internet is true!! I'm really just looking for ballpark baseline on my dual setup, after documenting "what they have" it wasn't making sense. I believe someone rebuilt these before me and probably didn't have their reading glasses on for the jet sizes.