Federal vs. calif carb differences? (1 Viewer)

[Bluegrass40]

Hey guys. Working on rebuilding a ‘76 Aisan carb (using @Pin_Head ’s videos, of course). I pulled it apart and based on the jet sizes it appears to be a California spec carb.

Primary main jet: 124
Secondary main jet: 200
Primary air correction jet: 55
Secondary air correction jet: 70

Are there any differences between the federal and California carbs other than jets? The truck I’m putting the carb on has been desmogged and I do not have to worry about smog etc in KY, so what would be the best way to set up this carb (jet size etc).

Here are some Pics of the date code and linkages for reference.




Thx!

 

[Bluegrass40]

So based on jet size it seems that the carb I have is a California spe. But when reassembling I was looking at the SOR carburetor ID chart and noticed that the wire form linkage for the accelerator pump matches a Federal spec carb, not a California spec. So, I’m not sure which one I have, or if it matters...

Still trying to determine what jet size would be best to run. If anyone has any insight, please share. At this point, I just put the jets back as they were.

Carb will be on a rebuild ‘78 2F.

Thx

 

[Dizzy]

If you are talking about the idle cut-off solenoid in the SOR pics, their California model carb is sporting a generic 16 to 18 gauge butt connector, not the original equipment.

Regarding jets, the whole thing is a mystery. Too lean and you have NOx emissions. Too rich and you have HC and CO emissions. The smog pump should have dealt with some of this, but not enough information is available for me to make any sense of this on my rig. However, I will take a stab at it for your rig. The 124 main jet is used for later models that might (1/76 to 12/78) have vacuum advance, and retard. Lean mixtures resulting from a smaller jet burn slower, hence the vacuum advance. However, in the chart, why the FJ55 model is sporting a different secondary main jet than the 40 remains a mystery.

 

[Bluegrass40]

Sent this message to the guy I bought it from...

“Got the carb rebuilt. There were several issues with it. Nothing super major but def could impact performance. All square now. We will see how it runs.

Do you know if the truck it came out of was a California spec truck? Where did the truck come from? Utah? Trying to understand the jets that were in there. They were similar to California spec jets but not exact. I think the carb body was not a California spec carb. Interested to know more about the truck it came out of.”

Got this back:

“Truck lived at 7250 ft elevation and often went up to 14500 ft based on the areas around it.
Truck live most of its life in Laramie Wyoming
Never California specs
Was bought in Nebraska but the guy I got it from
probably put smaller jets to lean it out and not over fuel in the long mountain hill climbs.”

Makes sense.

 

[Pin_Head]

I would ask Jim Chemoweth because he knows the jet sizes off the top of his head. If a jet is too small it leads to increased HC due to lean misfiring. If the jet is too large, you get high CO, but not necessarily HC unless it is too rich to fire.

 

[Bluegrass40]

Thx @Pin_Head

@FJ40Jim
Any guidance on jet sizing for a 76 federal carb on a Freshly rebuilt ‘78 2F? I am planning on just going with stock ‘76 settings unless you suggest different.

Thx!

 

[FJ40Jim]

The pictured carb is assembled incorrectly. The primary & secondary boosters are reversed.

Cali 2F carbs with a 124 main have a tiny 28mm primary venturi. "Normal" carbs have a 31mm. For a 28, keep the 124. With a 31 go to something in the 1.50 size.

 

[Bluegrass40]

@FJ40Jim great catch! That was a pic of the carb as it was when I received it. I didn’t even realized it was backwards when I disassembled. I believe I got it right on reassembly (thx to @Pin_Head ’s videos).

Thx for the Jet suggestions!

 

[Dizzy]

The pictured carb is assembled incorrectly. The primary & secondary boosters are reversed.

Cali 2F carbs with a 124 main have a tiny 28mm primary venturi. "Normal" carbs have a 31mm. For a 28, keep the 124. With a 31 go to something in the 1.50 size.

Wow, what is the Cali's secondary venturi diameter?

 

[FJ40Jim]

33mm

 

[Ackcruisers]

I’m rebuilding a 2/76 federal spec Asian carb. What is the optimal ratio of Venturi to jet diameter? Has anyone developed a mathematical equation yet?

The below Venturi‘s measure 28mm primary and 33 secondary.

I was planning on installing 150 jet in primary and 220 in secondary. (Desmogged 40 at sea level with a recent rebuilt motor) with good vacuum and compression). Running a vacuum advance non USA distributor with coil/igniter (semi electronic transistorized)

Given @FJ40Jim ‘s suggestion of running 124 jet in primary, I’m rethinking my approach. I also have a 136, 144 jet.

Given the small Venturi what Is the maximum I should use?

 

[FJ40Jim]

If it has a 28mm primary, then it's CA spec, AFAIK.
124 is about right, maybe drill to 1.25mm if the engine wants it.

 

[Ackcruisers]

Thanks, @FJ40Jim , I installed the 136 jet in the primary. Since my truck is desmogged, what is the harm in running the larger jet? Will it idle poorly with too rich of a jet?

 

[77mustard40]

I don’t think the primary jet being slightly larger will effect idle, a slow jet that is too small will (or did for me)

 

[FJ40Jim]

136 is too big for that carb, it will cruise at 12AFR dropping to 10AFR when the PV opens.

 

[Ackcruisers]

What is the AFR when running the 124 jet? I know below 10 is not healthy for engine but 10-12 is ok. I swapped the 136 for the 124 but now want to get an AFR meter to measure once I install.