Here is a pic of the Weber 34 with the top plate removed. There are five screws to remove to lift off the top plate. There is also a bolt under the electric choke & support bracket that needs to be removed also. When reinstalling, the choke cam needs to activated to allow the top plate to sit flat. I would hand center the gasket for top plate and hand insert all fasteners before tightening up any of them. Recommend the fastners be bottomed out slowly on reinstall. Snug them up slowly crossing over the carb many times.
The Idel Jets are external on the carb and the brass head bolts can be seen between the bowl for float and venture tubes. There is one on the primary side and one on the secondary side. All Jets are stamped with the size.
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Here is another angle of Idle Jet. Just below the top plate mating surface.
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The Run Jets are in the bottom of the bowl where the float would be. Here is a closer picture they are at the very bottom. The one on the right /choke side is the primary side for Idle & Run.
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I also had a quality control problem that affected my carb operation and the top plate removal and installs. In this pic you can see how the top plate GASKET IS CUT by a 1" x .020" casting flashing ridge along the bowl. In the pics of the bowl above you can see the ridge. This caused a complete carb failure on the Second REinstall and would not run period. I had to replace the gasket and grind down the flashing imperfection. I suggest you remove an flashing imperfection you find also. I am curious if others have different stock jets than mine due to this possible air leak. Looks like all Webers 34 sent with same jets from what I have seen so far, even though Weber tells me these are bench tested and set up for the Jeep 4.2 liter.
To solve the flashing problem I stuffed the bowl with rags, covered with packing tape, and covered the venturies with packing tape and used my dremel tool with fine stone or drum sander and flattened out the ridge till smooth. Blew away any metal filings from work with compressed air. Cleaned out bowl again and wiped and sprayed air. Tried to keep as clean as possible not to plug up the carb fuel passages with debree
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The Weber Jets are metric and the Jet Numbers are the metric hole size. I converted them to thousands of inch to compare and use % changes to see how much of a change I made. The jets I selected are much smaller.
When I put in the smaller Idle jets P/S 40/47 vs 35/35 my idle when up from 650 to 1100 rpms with no other changes. THE SMALLER IDLE JETS ALLOWED ME TO BACK OUT THE IDLE SCREW EVEN MORE.... BACKING OUT THE IDLE SCREW CLOSED THE PROGRESSION PORTS AND MADE THE RICH IDLE CONDITION EVEN BETTER. This was the second change of the Factory Stock STD Jets Idle 65/47.5 Primary/Secondary (P/S) that came with the carb in addition to swaping the P/S sides. I like the smaller RUN jets on Primary to get better fuel economy and the secondary to be bigger when you get on it, the gas pedal. Weber seems to ship the larger jets on the primary. I was able to back out the idle screw by 1 to 1.5 turns. My idle screw is now in about 1.25 turns from when it first touches or bottoms out. My manifold vacuum level also went up from 14/15" HG to 18/20" at 650/700 rpm idle with the smaller 35/35 Idle Jets and the idle screw at proper 1.25 turns range.
THE REASON..... WHEN THE WEBER 34 IDLE JETS ARE TOO... BIG.... USERS NEED TO SCREW DOWN THE IDLE SCREW TOO FAR AND EVEN CLIP THE LOCK SPRING TO TIGHTEN DOWN FURTHER TO GET THE ENGINE TO IDLE. WITH THE CORRECT/SMALLER IDLE JETS THE IDLE SCREW WILL ONLY BE TURNED DOWN APPROX 1.25 TURNS AFTER TOUCHING BOTTOM. WITH CORRECT IDLE JET SIZE THE IDLE SCREW SET APPROX 1.25 TURNS, THE THROTTLE PLATES ARE CLOSED, AND MANIFOLD VACUUM LEVEL SHOULD READ 18 TO 20 AT IDLE ON A SOUND ENGINE. OLD engines might be a little less. THE CLOSING OF THE THROTTLE PLATES CLOSES OFF THE PROGRESSION PORTS HELPING THE RICH IDLE PROBLEM EVEN MORE.
Once I got the smaller 35/35 idle jets my run jets were too lean now. The Idle Jets supply 15% approx of the run jet circuit. So kept increasing the Run Jets size till the plugs looked nice tan color. Run Jets 140/147 was just a little lean on the hwy. I drilled out the 130 to EQUAL A 145 and that combo of P/S Run 145/147 and Idle 35/35 that seems to run well for me.
You can also take one of the smaller jets and drill it out with english or metric drill bits to get jet size not offered. I drilled my 130 run jet to 145. This was my final setting used in Run primary jet. You may want to use two 147 / 147 Run Jets.
Please write down and post your stock jets that came installed on your new Weber 34 so we verify the same as mine or different. Also let us know how this set up ran on your 258 or even 232.
Regards,
Fred
Print the reference links in case they get moved or deleted. This is the most info you will find on the Weber 34 DGEC and Jeep I6 in one spot. This should also help you with the other Weber carbs also. AS ONE OF THE TUNE LINKS SAID.... ALL THE WEBERS RUN THE SAME!!
JETS Available:
Run Jets: 150, 147, 140, 135, 130, 125, 120, 115, 110
IDLE Jets: 65, 50, 47.5, 45, 35
Factory says the air correction jets do not normally change.
The Idel Jets are external on the carb and the brass head bolts can be seen between the bowl for float and venture tubes. There is one on the primary side and one on the secondary side. All Jets are stamped with the size.
Here is another angle of Idle Jet. Just below the top plate mating surface.
The Run Jets are in the bottom of the bowl where the float would be. Here is a closer picture they are at the very bottom. The one on the right /choke side is the primary side for Idle & Run.
I also had a quality control problem that affected my carb operation and the top plate removal and installs. In this pic you can see how the top plate GASKET IS CUT by a 1" x .020" casting flashing ridge along the bowl. In the pics of the bowl above you can see the ridge. This caused a complete carb failure on the Second REinstall and would not run period. I had to replace the gasket and grind down the flashing imperfection. I suggest you remove an flashing imperfection you find also. I am curious if others have different stock jets than mine due to this possible air leak. Looks like all Webers 34 sent with same jets from what I have seen so far, even though Weber tells me these are bench tested and set up for the Jeep 4.2 liter.
To solve the flashing problem I stuffed the bowl with rags, covered with packing tape, and covered the venturies with packing tape and used my dremel tool with fine stone or drum sander and flattened out the ridge till smooth. Blew away any metal filings from work with compressed air. Cleaned out bowl again and wiped and sprayed air. Tried to keep as clean as possible not to plug up the carb fuel passages with debree
The Weber Jets are metric and the Jet Numbers are the metric hole size. I converted them to thousands of inch to compare and use % changes to see how much of a change I made. The jets I selected are much smaller.
When I put in the smaller Idle jets P/S 40/47 vs 35/35 my idle when up from 650 to 1100 rpms with no other changes. THE SMALLER IDLE JETS ALLOWED ME TO BACK OUT THE IDLE SCREW EVEN MORE.... BACKING OUT THE IDLE SCREW CLOSED THE PROGRESSION PORTS AND MADE THE RICH IDLE CONDITION EVEN BETTER. This was the second change of the Factory Stock STD Jets Idle 65/47.5 Primary/Secondary (P/S) that came with the carb in addition to swaping the P/S sides. I like the smaller RUN jets on Primary to get better fuel economy and the secondary to be bigger when you get on it, the gas pedal. Weber seems to ship the larger jets on the primary. I was able to back out the idle screw by 1 to 1.5 turns. My idle screw is now in about 1.25 turns from when it first touches or bottoms out. My manifold vacuum level also went up from 14/15" HG to 18/20" at 650/700 rpm idle with the smaller 35/35 Idle Jets and the idle screw at proper 1.25 turns range.
THE REASON..... WHEN THE WEBER 34 IDLE JETS ARE TOO... BIG.... USERS NEED TO SCREW DOWN THE IDLE SCREW TOO FAR AND EVEN CLIP THE LOCK SPRING TO TIGHTEN DOWN FURTHER TO GET THE ENGINE TO IDLE. WITH THE CORRECT/SMALLER IDLE JETS THE IDLE SCREW WILL ONLY BE TURNED DOWN APPROX 1.25 TURNS AFTER TOUCHING BOTTOM. WITH CORRECT IDLE JET SIZE THE IDLE SCREW SET APPROX 1.25 TURNS, THE THROTTLE PLATES ARE CLOSED, AND MANIFOLD VACUUM LEVEL SHOULD READ 18 TO 20 AT IDLE ON A SOUND ENGINE. OLD engines might be a little less. THE CLOSING OF THE THROTTLE PLATES CLOSES OFF THE PROGRESSION PORTS HELPING THE RICH IDLE PROBLEM EVEN MORE.
Once I got the smaller 35/35 idle jets my run jets were too lean now. The Idle Jets supply 15% approx of the run jet circuit. So kept increasing the Run Jets size till the plugs looked nice tan color. Run Jets 140/147 was just a little lean on the hwy. I drilled out the 130 to EQUAL A 145 and that combo of P/S Run 145/147 and Idle 35/35 that seems to run well for me.
You can also take one of the smaller jets and drill it out with english or metric drill bits to get jet size not offered. I drilled my 130 run jet to 145. This was my final setting used in Run primary jet. You may want to use two 147 / 147 Run Jets.
Please write down and post your stock jets that came installed on your new Weber 34 so we verify the same as mine or different. Also let us know how this set up ran on your 258 or even 232.
Regards,
Fred
Print the reference links in case they get moved or deleted. This is the most info you will find on the Weber 34 DGEC and Jeep I6 in one spot. This should also help you with the other Weber carbs also. AS ONE OF THE TUNE LINKS SAID.... ALL THE WEBERS RUN THE SAME!!
JETS Available:
Run Jets: 150, 147, 140, 135, 130, 125, 120, 115, 110
IDLE Jets: 65, 50, 47.5, 45, 35
Factory says the air correction jets do not normally change.
