WEBER 34 DGEC, SOLUTION for Jets & Tune, Jeep 4.2 / 258
Well...... I just got done doing this for the WEBER 34 DGEC. I had a hard time getting help. The carbs do run very rich and yours may use the same jet or close. Please post what Run Jet and Idle Jet you have for primary and secondary onthe Weber 34 DGEC. Write down what you start with for Jets and settings, write down your changes and what you like, what has hesitation in primary or secondary, what is too rich or too lean. This should get you close or very close if things go the same for you as for my 1978 CJ7.
Caution when these things run tooooo.... rich the gas can wash the piston walls of oil and cause an issue. Too.... lean and get too hot and not good. I bet your plugs are black and sooty running very rich.
Here is a write up I did for the Cj Forum. This worked well for me and ALL HWY got 24/25 mpg with MSD ignition. REad on this will help you.....
This is what I have found to work on the WEBER 34 DGEC as far as IDLE & RUN JETS. The Weber 34 seems to run very rich and smoke. I think this will fix the operation for most of us. I have a 1978 CJ7 with Rebuilt 258 Long Block, Borla Header, more modern Jeep water jacket 2 barrel intake---so a very good base line. All pollution stuff removed and only vacuum stuff is Distributor, PCV Valve, Power Brakes. I updated my ignition with the TEAMRUSH & Grounds to Head & DuraSpark Ignition Modual. Still rich but helped. I then upgraded to Summits MSD, multispark ignition and helped a little more. So looks to be the Weber carb is too rich for stock or modified 258 as shipped. I also STRONGLY recommend the Holley Fuel Pressure Regulator set at 3 to 3.5 psi. Without the low pressure fuel the Weber will run rich from my reading & factory. Stock Weber set up not only makes the plugs black but also contaminates the oil with gas and makes it BLACK and lowers the oils protection level. If you have black oil change it.
Order these small group of jets and install them. Run your 258 around town and see if this helps with the smoking. Then pull a plug after 10 miles or so. Then run 10 miles of HWY and pull over and pull a few plugs and take a look. Good running plugs will be tan with small amount of black on the base ring of threads. This jet combo should get you very close.
PLEASE FAX Order to
631-863-2760 WEBER CARBS DIRECT AND INSTALL THEM. THESE SMALLER JETS JUST CAME INTO STOCK. THEN EMAIL ME BACK TO SEE IF THIS WORKS WELL. IF THIS FIXES YOUR CARB OPERATION THEN POST TO WEB HERE, JEEPFORUM , AND OTHERS CAN THEN ORDER THE SMALLER JETS.
The jets for the 34 are not on the web site as of today, they are replacing their phone system so hard to reach them on phone, so the fax is the easiest way to place this small parts order.
WeberCarbsDirect.com
Tech 800-871-3405 and gen # 631-863-2036
FAX 631-863-2760
NOTE: Choke side is Primary side of carb
FACTORY SHIPS WITH STD Jets Run 150/147 Primary/Secondary
FACTORY SHIPS WITH STD Jets Idle 65/47.5 Primary/Secondary
This is what was shipped with my carb. This JET SET UP smoked and plugs were black at idle and run.
ORDER:
New Jets Run 135/140/147 #73840.135 and .140 $5.95 ea
New Jets Idle 40/35/35 # 74404.035 jets Qty 2, one of .040 #74404.040 $6.60 ea
I suggest starting with this set up
Run 140/147 Primary/Secondary
Idle 35/35
And the Holley Fuel Regulator, can order from them also, orders over $49 ship for free.
Runs well 600 to 4000 rpms and pulls the whole way. Normal around town driving plugs look very nice, tan.. The hwy plugs are still tan but little lean. I drilled out the 130 Run jet to equal about a 145 using the 147 using the drill bit shaft as a feeler gauge. Looser than the .140 and almost as large as the 147. BOTH SET UPS WORK VERY VERY WELL. The smaller Idle jets, .035 / 035 will affect the RUN circuit and make it a little leaner. Factory informs the Idle Jets supply about 15% of the fuel when the carb is in the run mode.
Regards,
Fred Guercio
I sell nothing car/jeep related, nor do I have any relationship with Weber. THIS CARB DOES WORK PRETTY WELL AND WOULD LIKE OTHERS TO TRY THIS AND POST UP. ONLY THEN WILL WE KNOW IF WE HAVE A GOOD GENERAL SOLUTION FOR THE 258 JEEP.
Here is a good write up on how to tune the Weber.
http://www.justbrits.com/Articles/TuneWeber.html
Here is another group of write up(s) on how to tune a Weber and adjust the choke on weber.
http://www.izook.com/tech/samurai/engine/weber/weber.htm
http://www.izook.com/tech/samurai/engine/weberworks/weberworks.htm
Here is a good write up on how to read your spark plugs with pics
http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html
Well...... I just got done doing this for the WEBER 34 DGEC. I had a hard time getting help. The carbs do run very rich and yours may use the same jet or close. Please post what Run Jet and Idle Jet you have for primary and secondary onthe Weber 34 DGEC. Write down what you start with for Jets and settings, write down your changes and what you like, what has hesitation in primary or secondary, what is too rich or too lean. This should get you close or very close if things go the same for you as for my 1978 CJ7.
Caution when these things run tooooo.... rich the gas can wash the piston walls of oil and cause an issue. Too.... lean and get too hot and not good. I bet your plugs are black and sooty running very rich.
Here is a write up I did for the Cj Forum. This worked well for me and ALL HWY got 24/25 mpg with MSD ignition. REad on this will help you.....
This is what I have found to work on the WEBER 34 DGEC as far as IDLE & RUN JETS. The Weber 34 seems to run very rich and smoke. I think this will fix the operation for most of us. I have a 1978 CJ7 with Rebuilt 258 Long Block, Borla Header, more modern Jeep water jacket 2 barrel intake---so a very good base line. All pollution stuff removed and only vacuum stuff is Distributor, PCV Valve, Power Brakes. I updated my ignition with the TEAMRUSH & Grounds to Head & DuraSpark Ignition Modual. Still rich but helped. I then upgraded to Summits MSD, multispark ignition and helped a little more. So looks to be the Weber carb is too rich for stock or modified 258 as shipped. I also STRONGLY recommend the Holley Fuel Pressure Regulator set at 3 to 3.5 psi. Without the low pressure fuel the Weber will run rich from my reading & factory. Stock Weber set up not only makes the plugs black but also contaminates the oil with gas and makes it BLACK and lowers the oils protection level. If you have black oil change it.
Order these small group of jets and install them. Run your 258 around town and see if this helps with the smoking. Then pull a plug after 10 miles or so. Then run 10 miles of HWY and pull over and pull a few plugs and take a look. Good running plugs will be tan with small amount of black on the base ring of threads. This jet combo should get you very close.
PLEASE FAX Order to
631-863-2760 WEBER CARBS DIRECT AND INSTALL THEM. THESE SMALLER JETS JUST CAME INTO STOCK. THEN EMAIL ME BACK TO SEE IF THIS WORKS WELL. IF THIS FIXES YOUR CARB OPERATION THEN POST TO WEB HERE, JEEPFORUM , AND OTHERS CAN THEN ORDER THE SMALLER JETS.
The jets for the 34 are not on the web site as of today, they are replacing their phone system so hard to reach them on phone, so the fax is the easiest way to place this small parts order.
WeberCarbsDirect.com
Tech 800-871-3405 and gen # 631-863-2036
FAX 631-863-2760
NOTE: Choke side is Primary side of carb
FACTORY SHIPS WITH STD Jets Run 150/147 Primary/Secondary
FACTORY SHIPS WITH STD Jets Idle 65/47.5 Primary/Secondary
This is what was shipped with my carb. This JET SET UP smoked and plugs were black at idle and run.
ORDER:
New Jets Run 135/140/147 #73840.135 and .140 $5.95 ea
New Jets Idle 40/35/35 # 74404.035 jets Qty 2, one of .040 #74404.040 $6.60 ea
I suggest starting with this set up
Run 140/147 Primary/Secondary
Idle 35/35
And the Holley Fuel Regulator, can order from them also, orders over $49 ship for free.
Runs well 600 to 4000 rpms and pulls the whole way. Normal around town driving plugs look very nice, tan.. The hwy plugs are still tan but little lean. I drilled out the 130 Run jet to equal about a 145 using the 147 using the drill bit shaft as a feeler gauge. Looser than the .140 and almost as large as the 147. BOTH SET UPS WORK VERY VERY WELL. The smaller Idle jets, .035 / 035 will affect the RUN circuit and make it a little leaner. Factory informs the Idle Jets supply about 15% of the fuel when the carb is in the run mode.
Regards,
Fred Guercio
I sell nothing car/jeep related, nor do I have any relationship with Weber. THIS CARB DOES WORK PRETTY WELL AND WOULD LIKE OTHERS TO TRY THIS AND POST UP. ONLY THEN WILL WE KNOW IF WE HAVE A GOOD GENERAL SOLUTION FOR THE 258 JEEP.
Here is a good write up on how to tune the Weber.
http://www.justbrits.com/Articles/TuneWeber.html
Here is another group of write up(s) on how to tune a Weber and adjust the choke on weber.
http://www.izook.com/tech/samurai/engine/weber/weber.htm
http://www.izook.com/tech/samurai/engine/weberworks/weberworks.htm
Here is a good write up on how to read your spark plugs with pics
http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html