carb options, carb gurus speak up

[kchargis]

Poser suggested that I pose this question to the forum and if it goes well it will be added to the faq, so everyone with opinions speak up.

I have a 79 fj40 that the po desmogged and replaced with a weber, so I don't have the original carb or the smog stuff. I would like to go back to the aisin carb (obviously desmogged), so here are the questions:

1. What would be the best carb for me as far as years? Are the later any better than the early models?

2. What is the difference between a desmogged us carb and a non-us carb?

By the way, my 40 is a dd, 4.88s, 37" tires

kc hargis

 

[PabloCruise]

Jim C will tell you the 1976 carb is best...

Let me find that post

 

[PabloCruise]

Found it:

https://forum.ih8mud.com/showpost.php?p=977161&postcount=62

 

[kchargis]

where are the carb experts?

 

[Pighead]

I'm no carb expert. I have taken mine apart and put it back together a few times.
I like my '74 carb. It's got the mechanical secondary linkage which I like better than a vacuum operated secondary...

 

[FJ40Jim]

Poser suggested that I pose this question to the forum and if it goes well it will be added to the faq, so everyone with opinions speak up.
I have a 79 fj40 that the po desmogged and replaced with a weber, so I don't have the original carb or the smog stuff. I would like to go back to the aisin carb (obviously desmogged), so here are the questions:
1. What would be the best carb for me as far as years? Are the later any better than the early models?
2. What is the difference between a desmogged us carb and a non-us carb?
By the way, my 40 is a dd, 4.88s, 37" tires
kc hargis

Best is a subjective term.
Best power: 75-76 USA carb, properly desmogged & built.
Best fuel economy: 77-78 Cali spec carb, properly desmogged & built.
Worst carb: 1/79-7/80 USA spec

There are 40 US carbs and 100 different ROW carbs. There are hundreds of permutations of comparison. Can't say what the difference is without knowing what models we're comparing.

 

[Degnol]

Sort of a hijack, but related.


Jim, as long as we have you here, I am contemplating using that '74 carb with a large runner F('68) intake on my "new" 2F bored .030" over. Will that carb be sufficient for the larger displacement of the 2F over the F? Like Pighead, I have taken apart and redone several of the '74 carbs and at least can get them to run.And I also like the mechanical secondary. My motor is stock except for the overbore. New cam, lifters and no smog stuff as it is in a '66(or will be in a '66)
Therefore i have no VSV or any vacuum tubing except for the diz advance and the choke pulloff.
Oh, and public thanks for sending the plug!

Thanks,

Ed

 

[FJ40Jim]

Ed, the F carb will work fine on a 2F. I ran my 74 FJ55 w/ '82 2F engine like that. It is a little small for making max HP. But it is an easy install into an older truck.

 

[Doug_S]

I run a non-usa carb and love it. I don't have smog required testing where I live so there are no worries. The carb works great with no problems so far...

 

[dacicci]

not to talk you out of a stock carb but i run a motocraft 2150 it is 2 barrell full on and it runs like a champ. works killer off camber too. plus they are a dime a dozen. just get the right person to rebuild it. the only downfall is you need a holley adapter plate but they are not hard to come by. i bought mine for 25 dollars i have about a hundred bucks in the whole thing and it runs 400 times better than my other 40 with stock carb. not that the stocker cant work well also but for the price off the motocraft and the availibilty off the carb and parts it was well worth it just something to consider.

 

[kchargis]

doug_s what year is your non-us carb? where did you get it?

 

[kchargis]

Jim, what type of differences are we talking about between the 75-76 carb and the 77-78 cali spec carb (lets talk these two carbs)?

what type of economy are we talking for each, properly desmogged and lets just say stock set-up?

what type of power differences are we talking each, same senario. (does the 77-78 cali spec carb perform with significantly less power, etc)

Thanks Jim, you're the man!

I guess it would be no problem with setting these carbs up on a 3/79 fj40, right?

 

[Mark - CdnCruiser]

Carbs - cont'd

Another mini-threadjack -- hopefully related enough to not pi$$ anyone off...

How do you know when its time to replace/rebuild your carb?

I am struggling with keeping an idle, even after my 40 is warmed up. It seems to run alright when driving -- but will occasionally quit at a stop light without a little manipulation of the choke. I tried the vacuum leak search, was recommended SeaFoan (which it turns out I cannot get in Canuckland) and ultimately seemed to have a little success with a spray in carb cleaner.

The spray in cleaner seemed to keep it idling the day I treated it -- but by the following morning... the same struggles.

Is there any signs - other than poor function - to help decide when to replace/rebuild ?

Thanks -- Mark

 

[kchargis]

what about the 81+ carbs for the fj40, does anyone know how these are supposed to perform? Also, I was told by someone that the difference between the non-us and usa is the smog stuff and that a desmogged us carb is basically the same as a non-us, but this person wasn't 100%. Is the us and non-us carbs basically the same specs for each year ( for instance 76 us, 76 non-us)with the only difference being the smog equipment or does the year not imply anything and the us and non-us carbs are basically completely different carbs?

 

[Pin_Head]

Most of the electro-mechanical controls you see on 2F carbs is first generation electronic carb control, rather than for smog control (although they are related). It is there primarily to ensure the optimum air/fuel mix under more different driving conditions and to maximize fuel economy to meet CAFE requirements. If you don't have all the matching equipment, like the computer and VSV, obviously this stuff isn't going to work, so you will need a vacuum-mechanical carb.

 

[cruiser88]

on my 78 i had a f carb .worked well i did not get to drive it long new owner went with a holley 2100 carb he said it was a bit-h to get the spacer milled

 

[65swb45]

what about the 81+ carbs for the fj40, does anyone know how these are supposed to perform? Also, I was told by someone that the difference between the non-us and usa is the smog stuff and that a desmogged us carb is basically the same as a non-us, but this person wasn't 100%. Is the us and non-us carbs basically the same specs for each year ( for instance 76 us, 76 non-us)with the only difference being the smog equipment or does the year not imply anything and the us and non-us carbs are basically completely different carbs?

[I tried to get online a couple of days ago to answer this question, but my modem went down in the middle of the response. In the meantime, I forgot about it again. ]

The biggest advantage of the 81 up carb IMO is the idle-up diaphram and solenoid that was designed to compensate for the drag when you turn the A/C on. I was talking with Jim about this last year and thought that it would be cool to retrofit this to an older non-A/C cruiser just to put the idle up on a toggle switch to bump up your idle on steep uphills while you're busy working the clutch and brake pedals with your two feet. Other than that, the jetting falls somewhere inbetween that of a 76 and a 78 carb anyways IIRC.

As far as the rest of them go, you know Jim is on the money about staying away from the 79-80s unless you LIKE running a basically one bbl carb that looks like a 2bbl.

Beyond that, pighead is right that if you don't want to deal with the vagueries of vacuum secondaries, the F series carbs have a slight advantage in having mechanical secondaries.

Beyond THAT, it's all fair game. What no one seems to be getting out of the discussions when this comes up OVER AND OVER AGAIN is that the same carb can end up working differently on two different rigs because of the multitude of differences in engine and vehicle profiles. The compression of the engine, along with spark profile and timing are going to affect vacuum, which PROFOUNDLY affects the carb's ability to perform. Differences in exhaust manifolds and pipe diameters and muffler restrictions are going to influence vacuum with backpressure. Weight, gearing and tire size are going to affect WOT vacuum at different load speeds. Don't believe me: check your vacuum at WOT 3000rpm in 1st second and 3rd gears. Same rpm, same vehicle weight; different load, different vacuum.

IMO, the Aisan carbs were set up at the factory as the best guess scenario for the specific vehicle, weight and load-wise, and emissions [which again is load related] for that year. In most cases, the Aisan accomplishes it's task very well because it has several different circuits that suppliment each other well throughout the rpm range. However, there are times when the load is increased [bigger tires and lots of accessories on the rig] or the engine is not producing sufficient vacuum because of poor compression or less than optimum spark, and and the lack of performance is mistakenly diagnosed as a carburetor-based problem.

If that person then bolts on a different carburetor that performs well, they feel their diagnosis has been vindicated. While it is not impossible thet their old carb had a problem, it also quite probable IMO that if that is the ONLY change they made [and it usually isn't] then the odds are pretty good that the new carb was either set up from the factory for different load specs, or they got a carb that doesn't require as much vacuum in order for it's internal circuits to perform. Some of the aftermarket carbs that fall into this catagory share characteristics with your householdtoilet in terms of sophistication!

So, to answer your original question, other than the 3/69-9/69 2bbl and the 79-80, I like them all just fine, 1 and 2bbls alike, and think that any of them can be made into a very worthy carb for any application.

Hth

Mark A.

 

[N919HJ]

Let's wake this one up!

So, reading several threads I have found the general consensus to be that 79-80 carbs are the worst. My question is why, and can it be fixed without changing carbs and all the other little bits that go with that? Why are these carbs like only using single barrels carbs? I know I won't get anywhere fast in a Land Cruiser but if I'm leaving power and efficiency on the table, I'd like to know how to fix it.

 

[Pin_Head]

I'm digging up bones
I'm digging up bones
exhuming things thats better left alone....
Yeah tonight I'm sitting alone..
Digging up bones.

Randy Travis, 1986

 

[unklwedy]

Overly large runners on 68 intake manifold

DEGNOL

Many moons ago I reassembled a 1968 crusher and could not get it to perform well at low RPMs. Changing to later(1971) intake manifold solved low RPM performance. The reduced area of skinnier runners increased the velocity of air and gasoline mixture, and kept everything stirred up (I think). If yer after really high RPM performance(4000RPM) the 1968 intake manifold is the way to go.
unklwedy