PDA

View Full Version : Calling all CARB Guru's


PhatFJ
10-14-2011, 11:10 AM
I am in the middle of rebuilding the carb on my 1975 40. In the 2F fsm it states "Do not turn the AAP adjusting screw" I do not want to assume that this screw has never been adjusted throughout it's LONG life, therefor, does anyone know how to adjust the AAP setting or where the factory setting should be???

Thanks, Brian

subzali
10-14-2011, 11:14 AM
Lucky you to have an AAP. :rolleyes: I'd leave it alone. It's easy enough to adjust once you get it up and running and see what it does.

PhatFJ
10-14-2011, 11:26 AM
Lucky you to have an AAP. I'd leave it alone. It's easy enough to adjust once you get it up and running and see what it does.

Thanks Matt, I have left it alone. How do you adjust it when running? Do you know what the operational functions are and how to determine if they are correct?

Thanks, B

subzali
10-14-2011, 12:10 PM
Sorry Brian, didn't mean to confuse.

I don't think the AAP can be adjusted while running. But, IIRC it's not difficult to disassemble to the point where you can get at the screw, if desired. So once you get your truck back up and running again and see if the carb rebuild made any changes, you can decide if you're happy with it and go from there.

I am not sure what the screw does, but my guess would be that it controls either the volume or the rate at which fuel is dispensed from the AAP to the engine.

It's probably set from the factory to optimize power and emissions. Too much/too fast fuel, and you'll run too rich. Too little/too slow, and you won't have quite the "kick" you would normally. Again, just a guess.

RicardoJM
10-14-2011, 12:31 PM
The 22R carb has an AAP. As I recall, the manual only indicated to inspect the diaphragm was good and replace if it was bad. Without details on what the factory setting is (I understand that is the reason for this thread:D) I'd easily rationalize to myself that there is no way it had ever been messed with in its long life, make sure the diaphragm is intact and move on. :thumb:

PhatFJ
10-14-2011, 01:13 PM
Cool, thanks guys!! Another question about jetting, 144 is my primary jet, I have 2 options for secondary 162 & 230, what do you think??

Thanks

RicardoJM
10-14-2011, 02:00 PM
Cool, thanks guys!! Another question about jetting, 144 is my primary jet, I have 2 options for secondary 162 & 230, what do you think??

Thanks

Jetting is interesting and not as black and white as I'd like it to be. What size did you pull out? On the earlier (DD38) carbs the spare jets that were in the float bowl plugs were high altitude jets; one for the primary and the other for the power valve. It sounds like you have an FSM - does it have a table that could guide you?

To start with, I'd put in the size that was in there when you pulled it. Changing jets is pretty straight forward. With the proper tool (the one I have is not it, but I'm on the lookout for a good one), the jets can be accessed from the float bowl plugs and swapped in five minutes. Because I don't have the right tool, it takes a bit longer (15 minutes) which really is not any big deal.

As I have experimented with jetting, I have found the Primary jet is the one that makes the biggest difference. In my case 1.08 (FSM specification for high altitude) resulted in a sever off idle stumble and did not work. 1.12 was better and 1.14 is the sweet jet. IIRC, I swapped out the 1.14 in Air Randy's mule for a 1.18 and it is the sweet jet for his engine - it really perked it up on power and does not foul his plugs. So I swapped out to a 1.18 and the power was nice, but it fouled my plugs after a few thousand miles - so I'm back a 1.14.

subzali
10-14-2011, 02:03 PM
My '78 carb is using the factory jets at 136/171 on a '77 2F.

SOR says stock for your year is 144/230, though I don't understand why such a large jet would be used (especially at this altitude):
http://www.sor.com/sor/cat042d.tam

What did you pull out of the carb?

MDH33
10-14-2011, 02:08 PM
I'm running 114/180 in my '69 carb on a '77 2F.

subzali
10-14-2011, 02:15 PM
Hey Martin, what serial number is your block?

MDH33
10-14-2011, 06:50 PM
Hey Martin, what serial number is your block?

Let me look and I'll let you know. :wrench:

PhatFJ
10-14-2011, 08:58 PM
Jetting is interesting and not as black and white as I'd like it to be. What size did you pull out? On the earlier (DD38) carbs the spare jets that were in the float bowl plugs were high altitude jets; one for the primary and the other for the power valve. It sounds like you have an FSM - does it have a table that could guide you?

To start with, I'd put in the size that was in there when you pulled it. Changing jets is pretty straight forward. With the proper tool (the one I have is not it, but I'm on the lookout for a good one), the jets can be accessed from the float bowl plugs and swapped in five minutes. Because I don't have the right tool, it takes a bit longer (15 minutes) which really is not any big deal.

As I have experimented with jetting, I have found the Primary jet is the one that makes the biggest difference. In my case 1.08 (FSM specification for high altitude) resulted in a sever off idle stumble and did not work. 1.12 was better and 1.14 is the sweet jet. IIRC, I swapped out the 1.14 in Air Randy's mule for a 1.18 and it is the sweet jet for his engine - it really perked it up on power and does not foul his plugs. So I swapped out to a 1.18 and the power was nice, but it fouled my plugs after a few thousand miles - so I'm back a 1.14.


My '78 carb is using the factory jets at 136/171 on a '77 2F.

SOR says stock for your year is 144/230, though I don't understand why such a large jet would be used (especially at this altitude):
http://www.sor.com/sor/cat042d.tam

What did you pull out of the carb?

Yes, Matt and Ricardo the 144 and 230 were stock and also the ones I pulled out. That is what I put back in..
I put it all back together, started it up and it seems to run fine off idle but the idle seems jacked, not sure what I could have done or not done. Idle solenoid is working fine and I do not think there is a vacuum leak, I have adjusted the idle mixture screw (set to fsm rec of 1.5 turns out) and adjusted the idle speed adjustment, it will just stumble and die. I will look at it some more tomorrow.. till then any thoughts are appreciated..

PhatFJ
10-16-2011, 10:23 AM
So, yesterday i pulled the carb again (getting really good at this) verified that all is as it should be. While I had the carb off I took the opportunity to refresh the carb linkage at the same time (thanks Matt), re-tapered the idle mixture needle and re-installed the carb. It starts fine Idles better but not great, I took it for a drive got on C-470, it will get up to 65 just fine and seems to have some pep so I decided to go up 285, I found that I could not pull 285 if forth gear and had to burry the skinny in 3rd to maintain 50ish, this does not seem right but never having a stock 40 before I am not sure what to expect. So, I cam home and checked the timing, 7*, point gap .018, and reset the valves. I will do the paperclip test today but I still do not think I am getting any secondary. Any thoughts? I cannot imagine the jetting could be very far off, they are the stock jets :confused: anyhow, thanks for the ideas...

subzali
10-16-2011, 10:44 AM
I think having the timing advance to about 10-11 degrees BTDC helps at this altitude. Adjust it so the bb is just about to go out of sight through the timing window, or just below where the engine predetonates or "knocks".

Have you checked your vacuum? What do you mean it idles better but not great? Does it surge, or can you not get the idle down to spec? What do you mean by refresh the carb linkage?

PhatFJ
10-16-2011, 11:17 AM
I think having the timing advance to about 10-11 degrees BTDC helps at this altitude. Adjust it so the bb is just about to go out of sight through the timing window, or just below where the engine predetonates or "knocks".

Have you checked your vacuum? What do you mean it idles better but not great? Does it surge, or can you not get the idle down to spec? What do you mean by refresh the carb linkage?

Thanks Matt, I will reset the timing and see if that helps. The idle is a bit lopie not smooth, I have not hooked up a tac yet so I do not know the actual RPM. I rebuilt the throttle linkage taking out all the slop it is really tight now. I did put new plugs, wires and dist. cap on a while back maybe 100 miles. Where should I check the vacuum at?? there are no leaks that I can find..

Rezarf
10-16-2011, 01:37 PM
I agree with Matt, timing can make a BIG difference, I have run mine all the way out to 14* like Matt said, I usually just dial it up until it is just about out of view of the window on the bellhousing to start tuning.

FWIW, I dropped the points and went to an electronic ignition from an FJ60, and if I owned another 40 it would be in the top 3 things I would do before anything else.

subzali
10-16-2011, 09:20 PM
Brian, to check the vacuum you will want to connect a vacuum gauge to the brake booster port on the intake manifold. It's probably the easiest one to access.

PhatFJ
10-17-2011, 07:36 AM
Brian, to check the vacuum you will want to connect a vacuum gauge to the brake booster port on the intake manifold. It's probably the easiest one to access.

Cool, thanks Matt! Do you know what vacuum reading I should be looking for?

subzali
10-17-2011, 08:22 AM
At idle, I think at this altitude it should be a steady 13-14 in. Hg.

Can you describe "lopie not smooth" more specifically? Does the rpm increase then decrease and cycle, or what? :confused:

MDH33
10-17-2011, 09:03 AM
...The idle is a bit lopie not smooth, I have not hooked up a tac yet so I do not know the actual RPM. ... I did put new plugs, wires and dist. cap on a while back maybe 100 miles....

I agree with Matt, timing can make a BIG difference, I have run mine all the way out to 14* like Matt said, I usually just dial it up until it is just about out of view of the window on the bellhousing to start tuning.

FWIW, I dropped the points and went to an electronic ignition from an FJ60, and if I owned another 40 it would be in the top 3 things I would do before anything else.

Didn't check/replace the points when you did the plugs, wires, cap, rotor? I would check those and reset the timing like Matt and Drew suggested.

I did the electronic ignition like Drew, and I wouldn't go back.

PhatFJ
10-17-2011, 10:44 AM
Didn't check/replace the points when you did the plugs, wires, cap, rotor? I would check those and reset the timing like Matt and Drew suggested.

I did the electronic ignition like Drew, and I wouldn't go back.

Yep, did points as well..
Matt: I guess rough would be a better way to discribe the idle, it just is not as smooth as it was before I rebuilt the carb :(. By the way, what plugs are you using? I am going to pull the plugs today to look at them, as I recall, I just went with the cheep OEM plugs..

As far as the electronic ignition goes, I am trying to keep this as stock as possible.
Thanks again for all the help!! :thumb:

subzali
10-17-2011, 11:17 AM
From reading on MUD, it seems like the factory setting for dwell isn't exactly what most 2Fs like. Setting the points gap with a matchbook cover works well too, I think it's pretty close to the factory setting.

I use NGK plugs, which are supposed to be comparable to ND plugs. I forget the plug number, it's in the FSM and Haynes. Check your gap on the spark plugs while you have them out. A buddy of mine accidently collapsed a plug of his on his 4.0L Jeep, so it was running on 5 cylinders and he couldn't figure out why it was idling rough.

PhatFJ
10-17-2011, 11:56 AM
Update: Set the timing to 14* idles better 650rpm. Checked vacuum - 11inHG at idle. Took it for a short drive around home and it seems to be running well. I will take it for a spin back up 285 to see if the performance is any better. What do you think about taking it to an emission station just to have a look at the exhaust gas's re-jetting?? I will pull the plugs and take a look at them now..
ttyl..

b

RicardoJM
10-17-2011, 12:17 PM
It is sounding better. The vacuum you are pulling seems to be a tad on the low side. You have checked for vacuum leaks and not found any. Have you adjusted the valves?

Regarding your test drive, having to use 3rd going up 285 to keep above 50 is very consistent with my experience. If I leave it in 4th, too much speed bleeds off and I drop way down.

PhatFJ
10-17-2011, 01:06 PM
It is sounding better. The vacuum you are pulling seems to be a tad on the low side. You have checked for vacuum leaks and not found any. Have you adjusted the valves?

Regarding your test drive, having to use 3rd going up 285 to keep above 50 is very consistent with my experience. If I leave it in 4th, too much speed bleeds off and I drop way down.

Yes I have checked for vacuum leaks and can find none, I did adjust the valves yesterday :thumb:. Good to know about 285, was not sure what was normal so thanks... I wonder if the low vacuum is cause for the secondary seemingly to not come on strong :confused:. All of the emission components seem to be working properly.

subzali
10-17-2011, 01:32 PM
Brian, vacuum for the secondary comes from inside the carb. The vacuum is generated at the venturi; as air accelerates through the throat and expands on the other side a point of low pressure is created - also known as the Bernoulli effect.

But even still, 11 in. Hg of engine vacuum seems a little low for the 6000 feet or so elevation that you're at. Have you done a compression test or cylinder leak-down test?

Rzeppa
10-17-2011, 04:29 PM
I'm watching this thread to see if there will be anything I can try on my intermittently stalling FJ60...

PhatFJ
10-17-2011, 04:46 PM
Brian, vacuum for the secondary comes from inside the carb. The vacuum is generated at the venturi; as air accelerates through the throat and expands on the other side a point of low pressure is created - also known as the Bernoulli effect.

But even still, 11 in. Hg of engine vacuum seems a little low for the 6000 feet or so elevation that you're at. Have you done a compression test or cylinder leak-down test?

Did compression a while back and it was around 110 + or - about 3%, all were very consistent. So not very high but I think it still has a bit of live left in her, only has 76K on her.

subzali
10-17-2011, 04:53 PM
110 isn't bad for this altitude; that's around where mine is.

What did you do with the carb linkage when you adjusted it?

Have you done a cylinder leak-down test? The only thing I can think of is a vacuum leak, but I could be wrong.

How is the fuel in the bowl when it's idling? Did you get your float set correctly, and are you sure there's no junk in the carb? Did you replace the fuel filter or the fuel inlet filter on the carb?

PhatFJ
10-17-2011, 05:22 PM
110 isn't bad for this altitude; that's around where mine is.


What did you do with the carb linkage when you adjusted it?


Have you done a cylinder leak-down test? The only thing I can think of is a vacuum leak, but I could be wrong.


How is the fuel in the bowl when it's idling? Did you get your float set correctly, and are you sure there's no junk in the carb? Did you replace the fuel filter or the fuel inlet filter on the carb?

Glad 110 is acceptable :thumb:

Just tightened everything up, this was actually the throttle linkage per your other thread.

Have not done a leak-down

Fuel is right at the dot in the window so float seems fine, there is no junk in the carb, the fuel filter is less than 50 miles old and there is no filter on the carb other than the needle valve and it is clean. One strange thing I did notice right after I reinstalled the carb and it was running poorly, there was bubbling in the float bowl like there was air coming in from somewhere, I have not seen it since. The fuel level does not stay at the dot when not running, this is one reason I rebuilt the carb and it still goes down, everything is tight, I cannot figure out where the fuel could be going.. It is not leaking out of the carb. Looking at the FSM all the passages from the jets, and power valve all return to the float level. Now mine does have the AAP which is lower than the float but returns above float level :confused: By the way do you know if MAP gas will work the same or as well as propane when looking for an vacuum leak around the carb?

PhatFJ
10-17-2011, 05:45 PM
OK, I just went back out and looked at the carb, (after my run back up 285 which by the way went better, it was pulling petter in 4th gear) and ran my fingers under the carb, they were wet with gas, sure enough the large plugs that you remove to get to the jets were leaking (just a bit), I guess you really need to crank down on those copper gaskets. I will let you know if that solves my disappearing fuel in the bowel problem..

RicardoJM
10-17-2011, 06:29 PM
OK, I just went back out and looked at the carb, (after my run back up 285 which by the way went better, it was pulling petter in 4th gear) and ran my fingers under the carb, they were wet with gas, sure enough the large plugs that you remove to get to the jets were leaking (just a bit), I guess you really need to crank down on those copper gaskets. I will let you know if that solves my disappearing fuel in the bowel problem..

They need to seal, but don't ape on them:D.

Rzeppa
10-17-2011, 07:06 PM
They need to seal, but don't ape on them:D.

I had an issue in my '71 where I had leakage from the plug where the fuel return would go if it were so equipped, and the aluminum threads stripped when I tried to tighten it any more. I had to swap on a different carb top off one of my spares.

subzali
10-18-2011, 08:15 AM
Glad 110 is acceptable :thumb:



To clarify and follow-up, here's a link to a discussion we had about this last year...
http://risingsun4x4club.org/forum2/showpost.php?p=170461&postcount=15

How did you check your compression? Here's what *I think* I know about checking compression (some of which I didn't do in my post from back then, so my numbers are probably off):
When checking your compression, I think it's best to have a fresh battery so the starter cranks decently fast. You want to take readings with the air cleaner off and the carb throttle plate held open so the engine isn't creating a vacuum on the intake side. For each reading, you will want to crank the engine until you get at least 3 compression cycles.

Take a set of readings with the cylinders "dry"

Then squirt about a tablespoon of oil into each cylinder and take another reading "wet"

:thumb:

PhatFJ
10-20-2011, 01:23 PM
Well, the carb still leaks. It is not cracked, the jet plugs are tight (no leaking there), it must be leaking into the carb somewhere but according to the FSM, all the passages within the carb come back up to float level with one exception, the AAP and it is not leaking either :confused:. I will be driving this on the OOOoooooo run this weekend, if anyone wants to look at anything and here it run you can then... ttyl

PhatFJ
11-22-2011, 07:23 PM
OK, so about a week ago I noticed that the 2 rear manifold bolts were loose, so I tightened them down and ordered a new exhaust/intake gasket from SOR, along with that I ordered their gasket set between the intake and exhaust as well as replacing the heat flapper plate with the SOR stainless plate. I also pulled the carb again because I picked up a new Keyster carb kit for my specific year, it also included replacement jets so I put these into the carb. Got everything put back together and torqued to spec via the FSM, started her up and now I can not even get it to idle :mad: It seems that every time I touch this thing it gets worse. I checked the vacuum and it raised up to over 12in.hg now. I can't imagine the new gasket is leaking but I can't think what else it could be, this is very frustrating. I have checked and double checked all vacuum lines, I will get out the propane ad see if I can find some leaks :rant:

subzali
11-22-2011, 07:37 PM
sorry to hear of your troubles Brian...the vacuum does sound a little low to me though, if that helps...