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subzali
02-10-2011, 09:18 PM
So after doing tons and tons of reading on MUD and here over the past few days, I got the itch to finally get my carb off Brahma and check it out. See what I got. Here's what I found:

It's stamped 8 L 12.

That means it was made 12/12/78, designed for '78 Federal emissions.

It is a DD38/40, which means it is a 2 barrel (D) downdraft (D) and has a 38mm primary throttle diameter and a 40mm secondary throttle diameter.

The primary venturi is stamped 31, which means it is 31mm in diameter.
The secondary venturi is stamped 33, which means it is 33mm in diameter. Supposedly the largest stock venturi sizes are 31/35, which must be found on FJ60s I suppose:Here's Jim C. on the subject (http://forum.ih8mud.com/60-series-wagons/205289-carb-rings-can-you-change-them-out-2.html#post3042553). And from Ed Cook's writeup on Land Cruiser carbs (http://www.ih8mud.com/tech/carbinfo.php), it seems that earlier 2bbl carbs (I'm postulating for F engines) probably had 28mm primary venturis and 31mm secondary venturis. All interesting stuff.

Finally, what I've been curious about all along. As I've stated in other threads, the Brahma runs great at all elevations I've been to, with the lowest being the Moab area at 4,500 feet and the highest being Mosquito and Argentine passes at over 13,000 feet. Since I don't have flooding problems etc. like other have experienced and I don't seem to run lean I have always wondered what my magic numbers were for my jets. Here's what I found:

1st Main Jet: 136 (1.36mm)
2nd Main Jet: 171 (1.71mm)
1st Slow Jet: 75 (0.75mm)
2nd Slow Jet: 80 (0.80mm)
Power Valve: 80 (0.80mm)

EDIT: I also was curious about how everything was working, since I've been reading about fellas having issues with stuck balls etc. inside their carbs. Well my accelerator pump outlet check ball came out nice and easy, looked great. I couldn't get to the accelerator pump inlet check ball because I don't have forceps to reach the G clip and get it out. Will have to get one of those, but considering my AC pump works just fine, and nothing looked awry when I was looking down into that passage, I'm sure it's just fine.

I also need to get a split blade screwdriver for extracting the jets out of the fuel bowl. That would be the bees knees.

I also noticed that some of my throttle linkage was worn, especially the pieces on or near the firewall, so I should really take some time to address that at some point. There's lots of little washers, clips, and pins that go on the linkages, and it would probably be worthwhile for me to investigate to make sure everything is there and is correct. Unfortunately the parts diagrams and repair manuals don't really go into that level of detail, so I'm not sure how to find out how to make that all correct.

Finally, the PO has always maintained that the secondary never seemed to work properly. As I've learned more about these carbs in the last week or two, I'm considering pulling apart my secondary diaphragm and taking a look at it to see what condition it's in. It is only about $14 from NAPA to get a new one, so that's NBD if it's ripped. Or I might just throw the carb back on the truck and use a paperclip on the actuating rod to determine if the secondaries are opening.

Hope that helps someone with a 2bbl 2F carb. Most of the data we have on this forum is from 2bbl carbs for the F engine.

MDH33
02-10-2011, 10:10 PM
big difference in jet sizes between early and later Aisan 2bbl carbs.

I'm going to have to experiment with my '69 2bbl on my '77 2F in my '73 FJ40. :hill:

subzali
02-11-2011, 07:57 AM
Isn't the '69 carb considered to be the "lame duck" 2bbl?

From a quick glance at SOR's website jet sizes (http://www.sor.com/sor/cat042d.tam?xax=7883), it appears my carb is jetted to the factory settings. For "high altitude" they say the main secondary is 1.38mm. Unfortunately they don't show any info for the main primary or either of the slow jets or power valve.

I'd like to start doing a little experimenting myself to see what happens if maybe I do the following:

Main primary: 136 (1.36mm) - keep the same
Main secondary: 180 or 200 (1.80mm or 2.00mm) - richen up a little bit, though I've read somewhere that the "high altitude" secondary main is 1.44mm. Not sure if that's accurate though.
Slow primary: 50 or 60 (0.50 mm or 0.60mm) - to lean it out a bit.
Slow secondary: 60 (0.60mm) - to lean it out a bit.

Jacket
02-11-2011, 12:00 PM
So are you going for a full rebuild, or just satisfying your own curiosities? Are there problems that you want to solve?

I think I said this before, but the Napa kit was the one I found to be the most detailed and comprehensive (compared with two other Keyster kits). The Napa even came with a white paper that provided a lot of detail about the pieces and parts, including diagrams and the like. I don't recall if it labeled all the washers, links and springs, but I remember it being pretty good. As I think about it, I probably still have it in my stash. If I remember over the weekend, I'll look for it and see if it might be useful for you as another source of detail.

subzali
02-11-2011, 12:35 PM
Right now I'm just satisfying my curiosity. I'm still debating whether I want to spend the effort with this carb to do a full rebuild. It's not from the right model year and has some appurtenances that are extra and I can't hook up and I don't need, but it works for now, so I'm not spending too much effort on it. I'm considering sending this off to Jim C. as a core so he can send me back a correct one for my model year, but that's not very high on the "to do" list. And I'm really probably not going to play with the jetting (since it works), but I'm wondering out loud what differences it would make.

Did you record your jet settings on your carb? And if you can dig up that parts diagram that would be interesting to look over.

cbmontgo
02-11-2011, 01:06 PM
Matt,

As you know, I have also tooled with this jetting notion when I rebuilt my carb a couple of months ago. Here is the thread from 'Mud with pics of my jets when I removed them for the rebuild:

http://forum.ih8mud.com/40-55-series-tech/424692-carb-jets-question.html

I have 1.44 primary and 2.30 secondary, but this is a rig jetted for sea level and is a stock Federal 2F carb. My issue is that my truck runs beautifully here in the Denver area (Castle Rock at 6,300'), but I have not taken it above 8,000' yet.

Ricardo gave me a 1.41 jet which I plan to install in the coming weeks and test out. I have been told by the experts to leave a good running 2F engine alone, but I am still not sold on it running correctly at, say, Argentine Pass. I am looking forward to finding out for sure in the spring/summer. I think that the sweet spot may be between your 1.38 and my 1.44 primary for a 2F.

subzali
02-11-2011, 02:11 PM
Well mine is jetted for a '78 Federal spec (i.e. low altitude). And it runs fine from 4500 feet to over 13000 feet. That is mostly why I wanted to do this investigation, to see how it's jetted. I would tend to agree with most that if it seems to run fine (check your plugs and see if they are nice and tan or if they are black) then leave it. But I am also curious so I think it would be a fun experiment :D. But the big thing to remember is that even if it's jetter properly here you could see an 8,000 foot elevation difference while driving in the mountains. And as long as you're not living at 10000 feet remember that your excursions will be short enough to not worry about how precise your jet settings are. That is, as long as you're not running so rich that you're stalling out ;)

I think a jump from 1.44mm to 1.41mm will not hurt in your case (a lot better than jumping to 1.14mm), and it will be interesting to see how your 40 handles the altitude changes. I think you had some trouble with your 60 when you first moved here, so I understand why you're leary of stalling out at altitude.

cbmontgo
02-11-2011, 02:22 PM
Your 1.36mm is the primary jet though, correct? I was told by Jim Chenoweth on my '76 that the 1.44 primary is low altitude (sea level). I guess it really does just depend on the year?

subzali
02-11-2011, 02:32 PM
Yep, there are some changes year to year that I am not quite sure what to make of. I guess it probably has a lot to do with meeting emissions requirements of a given year: See the SOR table for jet sizes (http://www.sor.com/sor/cat042d.tam?xax=3805)

Once Toyota got to '79-'80 the jet sizes stayed about the same due to the HAC valve they added around that time (actually in '77 for certain models).

The 1.36mm is my primary (see above), but 1.44mm was the primary 2 years earlier (both for Federal emissions). For high altitude a smaller primary and a smaller power valve were typically supplied in carbs up through 1974. Ideally though the secondary would probably also change.

cbmontgo
02-11-2011, 02:59 PM
Yep, there are some changes year to year that I am not quite sure what to make of. I guess it probably has a lot to do with meeting emissions requirements of a given year: See the SOR table for jet sizes (http://www.sor.com/sor/cat042d.tam?xax=3805)

Once Toyota got to '79-'80 the jet sizes stayed about the same due to the HAC valve they added around that time (actually in '77 for certain models).

The 1.36mm is my primary (see above), but 1.44mm was the primary 2 years earlier (both for Federal emissions). For high altitude a smaller primary and a smaller power valve were typically supplied in carbs up through 1974. Ideally though the secondary would probably also change.

I never noticed that the sizes changed from July '76 to August '76 (mine is a May '76 build). This may mean that mine will do fine up there at altitude with the 1.44? Very interesting. Makes me want to head up to Argentine tonight and test it out!

subzali
02-11-2011, 03:16 PM
Well 8/76 is technically the beginning of the '77 model year, so the emissions components changed (slightly). I know the carburetors are a little different; for one the power valve on a '77 is internally controlled while on a '76 it's externally controlled. The VSV and VCV arrangement changed slightly as well. The jets were also leaned out, probably again to reduce emissions (though I know some emissions increase a little under lean conditions). But yes since your '76 and my '78 (carb) are both built for Fed/low alt. jetting, I would imagine your '76 would work just as well as my '78 (carb) does at altitude. Just drive to the top of Pikes Peak with it and find out :p:

cbmontgo
02-11-2011, 05:37 PM
Well 8/76 is technically the beginning of the '77 model year, so the emissions components changed (slightly). I know the carburetors are a little different; for one the power valve on a '77 is internally controlled while on a '76 it's externally controlled. The VSV and VCV arrangement changed slightly as well. The jets were also leaned out, probably again to reduce emissions (though I know some emissions increase a little under lean conditions). But yes since your '76 and my '78 (carb) are both built for Fed/low alt. jetting, I would imagine your '76 would work just as well as my '78 (carb) does at altitude. Just drive to the top of Pikes Peak with it and find out :p:

Cool stuff. Sorry to hijack your thread!

subzali
02-11-2011, 05:55 PM
No! I like web wrenching! :thumb:

subzali
02-24-2011, 08:14 PM
EDIT: Found out my power valve is 80 (0.80mm) tonight (edited original post). Got the carb buttoned back up and installed, ran it for a bit! Just about ready to bring it out of the garage again and get it back on the road!

cbmontgo
02-25-2011, 10:13 AM
EDIT: Found out my power valve is 80 (0.80mm) tonight (edited original post). Got the carb buttoned back up and installed, ran it for a bit! Just about ready to bring it out of the garage again and get it back on the road!

Cool! I am pretty sure that my power valve is a 1.20mm. Wonder if I should jet it down or if the primary jet change is enough?

Let me know how she is running!

subzali
02-25-2011, 10:30 AM
Seemed to run just fine last night, and I didn't change anything, so it should run great like it always has!

If I were you, I would lean out the power valve as well if you can find one and give it a try. 1.2mm seems rich to me, and it seems Jim C. recommends 0.75 to 0.80 even for sea level operation. That with either the 1.44mm or the 1.41mm 1st main would probably be a good combo, if I had to guess...

cbmontgo
02-25-2011, 10:42 AM
Seemed to run just fine last night, and I didn't change anything, so it should run great like it always has!

If I were you, I would lean out the power valve as well if you can find one and give it a try. 1.2mm seems rich to me, and it seems Jim C. recommends 0.75 to 0.80 even for sea level operation. That with either the 1.44mm or the 1.41mm 1st main would probably be a good combo, if I had to guess...

I just installed a 1.38mm primary and it seems to run really well down the road in Castle Rock. I also left a message with Groove Toyota today about ordering a .80mm power valve. I am going to try this combo up at elevation and see how she does.

I also have a 1.41mm primary that Ricardo is letting me try; I may use this one if the 1.38mm primary seems to lean. So far so good though.

With that said, I am still running my 2.30mm secondary. I guess I am going to leave this one alone?

subzali
02-25-2011, 10:59 AM
I would unless you find a reason to change it. Prior to '74 Aisan carbs came with a spare 1st main and a spare power valve for high altitude. No spares were provided for the 2nd main. Yours is more rich than mine, but there may be a difference in the secondary circuit between your carb and mine, your boosters may be different, etc. You may feel a little more oomph than I do when your secondary kicks in, maybe not.

Just keep checking your spark plugs periodically to gauge how it's running. White = too lean, Black = too rich. Tan is just right :thumb:

cbmontgo
02-25-2011, 11:01 AM
I would unless you find a reason to change it. Prior to '74 Aisan carbs came with a spare 1st main and a spare power valve for high altitude. No spares were provided for the 2nd main. Yours is more rich than mine, but there may be a difference in the secondary circuit between your carb and mine, your boosters may be different, etc. You may feel a little more oomph than I do when your secondary kicks in, maybe not.

Just keep checking your spark plugs periodically to gauge how it's running. White = too lean, Black = too rich. Tan is just right :thumb:

Thanks Matt. I will keep you posted and will continue to hijack your threads in the process. :D

cbmontgo
03-11-2011, 10:38 AM
Matt,

Thanks to Ricardo and his availability of jets, I am running more "appropriately" here at elevation. I have a 1.38mm primary, 1.80mm secondary, and a .80mm power valve. Seems to have more power up hills and runs beautifully. Hope to see you up at Mosquito Pass this year!

Thanks again for your thread here; it has been a big help on clarifying how local FJ40s are jetted.

SteveH
03-11-2011, 01:08 PM
I rebuilt my all-stock Federal spec. '78 carb in (gulp) 1990 and haven't rebuilt it since. It runs well and better than any other carbureted vehicle I have ever owned.

The secondary diaphragm was ruptured, and I replaced that, but I did not rejet. It runs great at 7000' and I've had it at sea level and 13K feet. It definitely runs rich at 13K and occasionally blows out a black cloud. Some of that would be from the unadjusted idle mixture, however. High speed jetting is only part of the whole occasion.

I once tried rejetting a '78 carb, and it was tragic - whatever I did, the vehicle wouldn't run, so I gave up on that carb. In general, if your truck runs well, I would leave the jets alone. The biggest wear items I have seen in LC carbs are the accelerator pump and the secondary diaphragm. My '78 ran so much better after I just 'put a kit in it' and re-set the float and mixtures, etc. that I have driven it since then with no changes.

If this were an Edelbrock or Holley, rejetting might be far more important. Fortunately, Toyota's carbs are so robust that they basically work well with factory jetting under most circumstances. YMMV - just what I have experienced. If you find a miracle jetting situation that really results in better power, lower emissions, etc., then I'm all ears.