Does anyone have a clear photo of the Hemi carb jet locations. The one I have one my phone is not great on the bottom
Hemi carb jetting photo
- Thread starter dan juhasz
- Start date
This for 66 carbs 4139 front 4140 rear
If that's from a NHOA or an NeHOA newsletter it might be California jetting "CAP" @Dragon Slayer . I post one that looks like a few years ago.
Thanks Fran, another question . On the secondary booster Venturi’s, service manual says there is a right and left. They do not say how to distinguish. These carbs were butchered. Looking at the underside of the venturis there is a larger and smaller holes, any idea if the larger holes on both face to the outside or the inside of the carb? If I put the large hole to the outside it would line up with the slot I’m pointing to. If I put the large holes to the inside the smaller hole would line up with the slot.
Dragon Slayer is the guy to ask. Know plenty about carbs. That's why I typed his name to bring attention to thread.
My secondary carb is a 4343s , I put 4140s but I was mistaken.
Is this a 67 car? Is a 4343 Carter a correct car for a 67? I have the correct booster numbers and locations for 4139/4140 carbs for 66 but that probably won’t help. The boosters have a part number cast in them.
From memory I thought there was a small protrusion in the seat in the carb body and a small corresponding recess in the bottom of the boosters, so that they could only seat fully in their proper locations. I think I see it in your pictures - it’s right off of the bore in the carb base.
The small bump outs in the booster seat shows up pretty clearly in this photo of my carbs. The boosters have a corresponding recess.
From memory I thought there was a small protrusion in the seat in the carb body and a small corresponding recess in the bottom of the boosters, so that they could only seat fully in their proper locations. I think I see it in your pictures - it’s right off of the bore in the carb base.
The small bump outs in the booster seat shows up pretty clearly in this photo of my carbs. The boosters have a corresponding recess.
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Thank you, you are correct. It looks like these were in the wrong location at one time also as the bump out has a definite flat spot. Unless that is the way they look.
Could you tell me if I have the correct orientation of the jets, I believe it to be just as the 4140 would be. The 4343 is also tagged as the front ( secondary) carb for 426 Hemi from 66 through 71.
4343 is correct for 67, have one on my car until I get my 4140 rebuild. The jetting is read top to bottom front carb on top. Primaries are the same. PS means passengers side, OP think it means operators side.
actually I just read it today researching. OP stands for opposite pump, PS stands for pump side. Referring to accelerator pump.
Right - that (OP & PS) threw me also the first time I came across it. I’m not sure how much this will help but here is what I have for my carbs. The jet sizes in () are what Dragonslayer confirmed for stock. My carbs were messed up on jets, and rods in the front carb. The numbers right above the bores are the booster numbers that Dragonslayer also confirmed.
Appreciate it, thank you
Just so I’m clear, what is marked as the front carb is the choke less unit and the one marked as rear is the primary carb with choke. Is that correct?
Here is what George provided me on my carbs from the Carter data in this thread 66 Hemi jetting
Front Carb Jets
Pri Both 159 .089
Sec OP 159 .089
Sec PS 171 .1065
Low Spd Jet .035
Rear Carb Jets
Pri Both 159 .089
Sec OP 158 .082
Sec PS 175 .073^ Carter states this but FSM said .080
Low Spd Jet .035
Meter Rods
Front Both 136 .071x.061
Rear Both 440 .0665x.058
Your venturis are correct. The 678 does not have a secondary discharge port, a characteristic of hemi carbs. The 348 would, all part of distribution of fuel I am sure.
Is your intake cut open like the vanke mod? If not, I would go back to stock or as close as possible. Then tune from there. To do it right you need to use an o2 sensor and AF ratio meter.
Remember the front carb is high speed high throttle open only. Progressive linkage. So getting your rear carb dialed in for idle cruise. Since your jets do not have orig numbers they clearly were changed at some point. My L5 66 carbs had original jet numbers in them.
Front Carb Jets
Pri Both 159 .089
Sec OP 159 .089
Sec PS 171 .1065
Low Spd Jet .035
Rear Carb Jets
Pri Both 159 .089
Sec OP 158 .082
Sec PS 175 .073^ Carter states this but FSM said .080
Low Spd Jet .035
Meter Rods
Front Both 136 .071x.061
Rear Both 440 .0665x.058
Your venturis are correct. The 678 does not have a secondary discharge port, a characteristic of hemi carbs. The 348 would, all part of distribution of fuel I am sure.
Is your intake cut open like the vanke mod? If not, I would go back to stock or as close as possible. Then tune from there. To do it right you need to use an o2 sensor and AF ratio meter.
Remember the front carb is high speed high throttle open only. Progressive linkage. So getting your rear carb dialed in for idle cruise. Since your jets do not have orig numbers they clearly were changed at some point. My L5 66 carbs had original jet numbers in them.
Dragon Slayer
Well-Known Member
The 4139 was the front carb for both 66 and 67.
The 4343 is the 67 NON CAP carb for 67.
The venturi's and meter rods are the same for the 4140 and 4343. The venturi's have cutout on the bottom so that they fit in the body only one way.
For the rear venturi the large hole picks up fuel for the secondary discharge port. The small hole was cut to make the passage for discharge. It will seal on the gasket.
348 is on the Pump side and 678 (no discharge port) is on the choke side, or Opposite pump side.
The main difference on the 4343 was jetting change and a top that has the vent lever.
4343
.089" jet both sides of primary.
.080 secondary pump side
.083 secondary opposite pump side.
The 4343 is the 67 NON CAP carb for 67.
The venturi's and meter rods are the same for the 4140 and 4343. The venturi's have cutout on the bottom so that they fit in the body only one way.
For the rear venturi the large hole picks up fuel for the secondary discharge port. The small hole was cut to make the passage for discharge. It will seal on the gasket.
348 is on the Pump side and 678 (no discharge port) is on the choke side, or Opposite pump side.
The main difference on the 4343 was jetting change and a top that has the vent lever.
4343
.089" jet both sides of primary.
.080 secondary pump side
.083 secondary opposite pump side.
mrhemi
Well-Known Member
The Hemi actually idles on the front carb as well. There is a detailed procedure in the FSM to get this balance correct.
That was actually part of the quote from Dragonslayer - I think he was primarily talking about the power circuits at the time. But yes, you are correct that both have idle circuits. Some years have adjustment screws on the front carb and some don’t.
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mrhemi
Well-Known Member
The original '69 carbs from my car had the idle screws sealed with lead plugs, so non-adjustable. Someone prior to my ownership had mangled the carbs trying to drill out the lead plugs. I have been using a set of '68 carbs on the car for over 40 years. They had adjustable idle mixture screws from the factory. That does make it much easier to balance the carbs properly.
Dragon Slayer
Well-Known Member
68 and up hemi front carbs come with hidden idle screws. Someone added those front idle mixture screws. Which would be easy enough to do, though not OEM look.
66-67 had idle mixture screws on the front carb. 66-67 were also unique in they were bypass carbs and used an air valve to set idle. Vice idle screw that would open the throttle valves.
68-71 are also unique in they added a fixed secondary idle circuit on the rear carb. There is a port below the secondary throttle blades that emit fuel at idle speed, besides the typical secondary discharge transition circuit AFBs have. Pretty sure all this had to do with distribution at low speeds for the street hemi. Additionally preventing misfire of a cylinder due to fuel distribution.
66-67 had idle mixture screws on the front carb. 66-67 were also unique in they were bypass carbs and used an air valve to set idle. Vice idle screw that would open the throttle valves.
68-71 are also unique in they added a fixed secondary idle circuit on the rear carb. There is a port below the secondary throttle blades that emit fuel at idle speed, besides the typical secondary discharge transition circuit AFBs have. Pretty sure all this had to do with distribution at low speeds for the street hemi. Additionally preventing misfire of a cylinder due to fuel distribution.
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