OEM carburetor trivia!! 13 questions. (Another Weber delete threat. )

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firefighterjed

firefighterjed

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Part of the great joy of owning an older Landcruiser is how completely serviceable they are. I love working on my rig and enjoying the risks and rewards that result. I know that the gold standard for carb set up is to send it off to Jim C or Mark, but the stubborn ass that i am wants to do everything myself.

I’m getting ready to delete the weber in favor of an OEM carb. I’ve rebuilt the OEM carb, but I have a some more detailed questions about the ideal initial setup for my particular vehicle. Maybe you’ve got some insight that can help.

I’ll outline my project and pose my questions at the bottom.

Current set up is 1976 FJ40 with DUI/HEI, Headers, Weber 32/36, smog is all deleted and capped/plugged. 2F, H42, stock t-case , 4:11 diffs turning 33x12.5r15.
I want to return to an OEM carb.
I was given a 21100-61072 casting stamped 6G2. PJohnson said someone gave it to him, and to pass it on if he didn’t use it. Lucky me!

Cruiser Outfitters sold me a keyster kit including a secondary diaphragm and I cleaned and replaced all the seals, gaskets and o rings.
Cleaned all the metal parts in Barrymans in an ultrasonic bath.

Slow jets are 55 and 70
I have ordered an assortment of main jets from 125-150 and 180-220

I used the FSM and a Haynes to guide my initial setup for all adjustable parts. Choke gap, choke breaker angle, Throttle stop, WOT, high idle, and secondary kick up, etc are all set to the federal spec in the FSM. When I was setting the secondary kick up i found that the primary throttle shaft was slightly bent. It appears that this had been dropped. I was able to straighten the shaft and eliminate the slight cam type motion that was being cause.

I live at 3500 feet in idaho. This is a weekend driver with trail adventures but no real crawling. I go to 6500’ often and seldom go to lower elevations.

My questions are these:

1. What makes this “California spec” carb different from a federal or a world market carb?

2. What main jets would you recommend as a starting set for me?

3. I can pull plugs and read them for rich/lean, are there other things to look at to suggest changing main jets?

4. Do I need different slow jets?

5. Are there baseline adjustment specs that I should use that are different than the federal spec in the FSM?

6. I wasn’t able to get the full 9.5mm of throw in the accelerator pump plunger. I know the plunger hits bottom right as the rod from the throttle cam gets to its apex, but at idle position the plunger is only lifted up about 8mm. (In the attached pic the rod is on the wrong side of the throttle cam, I’ve since flipped it to the outside.)

7. Where does the choke breaker get it’s vacuum from? Im desmogged. My only other vacuum lines are distributor advance, secondaries, and brake booster.

8. Should I even keep the choke breaker? I noticed it’s not on world market carbs

9. Is there a better cap for the EGR pipe off the riser? This white one is tight and secure, but the zip tie seems hokey so I thought I’d ask.

10. Is the vacuum source next to the idle mixture screw the proper source for the distributor?

11. I have a working fuel return line that is currently capped, so convenience has no bearing here. Is the return line a good thing?

12. I should I cap it at the carb too? ( fuel pump is recently replaced OEM mechanical)

13. The riser/heat shield that insulates between the intake manifold and this carb has a vacuum port. What attaches there ?



Thanks in advance everyone!


8BCE087A 6517 48A3 8E16 FA71038142DC


0699B0AA 2D37 4B68 B0B8 28691038D987


929D2773 CA39 4408 BA42 716241EB7820


E8FFD93B 8DF7 4766 A64F 9202718265BA


14AB3773 3C2D 4FFA 830D FD5703D0C8AE
 
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firefighterjed

firefighterjed

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#13 would be the PCV hose connection (at least it is in early rigs).
PCV goes to full vacuum? I understood that it usually goes to the air cleaner.
 
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middlecalf

middlecalf

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I understood that he usually goes to the air cleaner.

That‘d be a vacuum leak then. Valve cover vent tube (if there is one) goes to the air cleaner to get clean air. PVC gets full vacuum to get rid of built up blowby fumes under pressure in crankcase. If no pressure, then PVC valve closes and keeps that below-carb connection from becoming a vacuum leak, but if it isn’t working or stuck then it can be a good one 😂 .
 
firefighterjed

firefighterjed

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That‘d be a vacuum leak then. Valve cover vent tube (if there is one) goes to the air cleaner to get clean air. PVC gets full vacuum to get rid of built up blowby fumes under pressure in crankcase. If no pressure, then PVC valve closes and keeps that below-carb connection from becoming a vacuum leak, but if it isn’t working or stuck then it can be a good one 😂 .
Ahhh yes, I was remembering the valve cover breather rather than the PCV. thank you! #13 solved.
 
mattressking

mattressking

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I'm going to take a stab at the full list, Jed. Answers below.

1. What makes this “California spec” carb different from a federal or a world market carb?
Carb specifically, just the jetting I believe. California saw 1.24 primary, Federal saw 1.44 primary. Main stayed the same with 2.30.
2. What main jets would you recommend as a starting set for me?

I'd start with 1.44 and 2.30 as a baseline and ensure vacuum is above 16inHg at idle, warm with timing @ 10*
3. I can pull plugs and read them for rich/lean, are there other things to look at to suggest changing main jets?
If the truck pulls smooth when cold and hot, that is enough usually. You'd need to sniff the pipe on rollers or hook up a wideband to get an idea of mixture through powerband. Not necessary here, 2.30 is pretty fat, no danger of lean condition. High altitude jetting (assuming non ethanol gas in the 70s) saw a 1.38 for main. The trick for main jet testing is do a pull with pedal to the floor, then cut the truck off, check plugs. That will indicate how the motor looks right at shutdown.
4. Do I need different slow jets?
I can't say I'd see a reason why you would, but Jim or Mark would be the best resource here.
5. Are there baseline adjustment specs that I should use that are different than the federal spec in the FSM?

Same adjustment to get it going, final tweaking is done on the truck at your altitude using vac gauge/tach.
6. I wasn’t able to get the full 9.5mm of throw in the accelerator pump plunger. I know the plunger hits bottom right as the rod from the throttle cam gets to its apex, but at idle position the plunger is only lifted up about 8mm. (In the attached pic the rod is on the wrong side of the throttle cam, I’ve since flipped it to the outside.)

So this is fixed?
7. Where does the choke breaker get it’s vacuum from? Im desmogged. My only other vacuum lines are distributor advance, secondaries, and brake booster.
Initially the emissions computer, but desmogged you route to manifold vacuum - so any port off the manifold you have, or add one.
8. Should I even keep the choke breaker? I noticed it’s not on world market carbs

If it works, keep it. You could remove the linkage for the TP portion.
9. Is there a better cap for the EGR pipe off the riser? This white one is tight and secure, but the zip tie seems hokey so I thought I’d ask.

Just a large EPDM type cap is sufficient. The trick is to use a 60 series carb insulator which acts solely as a spacer, no EGR pipe.
10. Is the vacuum source next to the idle mixture screw the proper source for the distributor?

Yes, it is ported vacuum.
11. I have a working fuel return line that is currently capped, so convenience has no bearing here. Is the return line a good thing?

Not necessary, but if everything is there, why not connect it?
12. I should I cap it at the carb too? ( fuel pump is recently replaced OEM mechanical)
Yes, cap it off at the carb if you don't use the return line.
13. The riser/heat shield that insulates between the intake manifold and this carb has a vacuum port. What attaches there ?

That is for a later truck and used for Evap. Not needed for you, but it is a vacuum source if you need one.
 
77mustard40

77mustard40

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First up, fine looking 40!

I'm not smart enough to take a stab at all the questions, but I can share my experience. A lot of my thread relates to a manifold vacuum leak and mistakes I made with my first carb rebuild, but I did have idle issues that ultimately came back to main & slow jet sizes. I'm at a lower altitude and I'm running 150/65 slow on the primary side and 220/85 slow on the secondary side. I initially built the carb with 141/50 on the primary side but could not get a consistent idle and was coached up to the current jets by Jim C. I pulled vacuum for the choke breaker and PV from the gas filter on the front side of the intake manifold (my PV is not internally ported for vacuum). IIRC I think I capped the EGR with a short section of hose and a bolt with hose clamp. Anyway here is some light reading from 10 years ago...

 
ToyotaMatt

ToyotaMatt

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Your before and after BACK and FORTH Effects shots above is a NEW and Refreshing professional photography approach seldom used here on MUD


it made me eager to see the next one and next one and so forth JED


thanks for sharing your unique and indeed subscribed build thread status in the way u do .



kindly matt




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