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Unread 08-13-2014, 07:09 PM   #1
illinicj
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Carter BBD post Rebuild install not going well, advice needed please

I rebuilt my carb Monday night. I did this because in 12 years I never had done it, and it was starting to behave as if the venturis were clogging as I dealt with many years ago. Stumble and stall at idle. 79 258 with 4.0 head swap, auto trans.

The rebuild seemed to go well, easier than I expected to get it all clean and put back together. The real head scratcher was that I found my idle screws bottomed out. Both of them. I've never touched them, so it's been like this forever. It's run great all these years... Smooth idle, but a little rich smell. Only regular complaint has been a flat spot in the acceleration on the highway that I never felt like chasing down. Anyway...

Bolted on and tried to get it running last night. I got it going and warmed up but it was rough. Couldn't keep it running without the choke mostly closed though. Open it any more and it would die quickly. I eventually found a rotted vacuum hose going to my quadratrac shifter. Plugging that helped smooth it out a bit and I wonder if that was my problem in the first place. Still wouldn't run without the choke closed.

After searching for more vacuum leaks to no avail, I decided to cap all the vacuum ports to just eliminate the possibility from the other hoses. Tried running again tonight. Same thing. I've sprayed carb cleaner all over around the intake at the head, base of the carb, throttle shaft, and detect no leaks. Fuel filter is new.

I figured I must have screwed something up inside the carb and took it back apart again. I see nothing wrong. Put it back together and tried again. Now I'm getting it to idle a little better, about 1k rpm, and can keep it running with the choke open. I have the curb idle screw all the way in to get it there. Vacuum is low, around 13 or so.

Now that the choke is open, I can see gas just dripping out of the venturis. I know these passages are already drilled out from years ago and cleaned out well now. Why would gas be just dripping here? When I squirt carb cleaner down the throat, it idles better, vacuum goes up. That dripping fuel is not atomizing and burning... I stink like gas.

I'm sick of battling it all week and taking a break. Looking for advice on how to get her back on the road. These N IL summers are too short to have her stuck in the garage. The fact that it's a self inflicted wound makes it that much worse.

I'm considering a reman carb if I can't sort it out pretty quickly. I also found these Crown carter clones as low as $235. There is also the 2100 swap... Thoughts on these "plan B's"? I'm tempted to buy the swap kit on eBay and be done with it. Thinking of spending the money on any of these options kills my pride...

Sorry for the long post. I'm sure I still forgot some important info.

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Unread 08-13-2014, 07:27 PM   #2
86cj74.2L
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What are your idle mixture screws set to after the rebuild? After a rebuild they will need readjusted.


I would start at 3 1/2 turns out and then preform the lean best idle procedure. And set your idle at 600rpm in park-neutral and continue the lean best idle until your idle rpm stops climbing.

You have the big and small check ball where they belong?
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Unread 08-13-2014, 07:46 PM   #3
illinicj
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That was my plan after reading the instructions before I started. Then my CJ got involved... I found them bottomed out and know that's not right. I started at 4 turns out. After getting a somewhat stabile idle tonight, I decided to try adjusting them and see what happened. I can't set to 600 because I can't bring my idle below 1k without it dying. I turned the screws in half a turn at a time together. They eventually bottomed out and I saw/heard no difference. I think the throttle is open too far to set the idle circuit. Vacuum gauge reads a shaky 13 or so during this...

Yes big and small check balls are in the right places. No thanks to my rebuild kit, which gave me 2 small balls. I reused the old, which showed no sign of wear.
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Unread 08-13-2014, 07:58 PM   #4
Marshal
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Check the setting of your fuel metering pins and accelerator pump. I had to tweak mine because I didn't set them back properly. First set your idle screws where they should be. Then take off your air filter, and the cover for the pump and pins. Start with the pins lean (all the way down) and lift them up a tiny bit at a time until you can get it to idle. Keep adjusting until it decides it doesn't like what you're doing, and back it off to the setting it ran best in and lock it there.

Next you'll do your accelerator pump. Kinda the same theory of adjustment. Start it off all the way down, and lift it up a little. Snap the throttle and see what it does. Probably sputter and try to die, or shoot a fireball out the throat of the carb. Those are neat! Keep going until it responds like it's supposed to when you snap the throttle.

Once you have the metering pins and accelerator pump set, you can do the final idle adjustment with your set screws.
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Unread 08-13-2014, 07:59 PM   #5
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Have you set the float levels, metering rods and accelerator pump using the method in the manual?

There is a BBD overhaul manual on the Net. I have a copy but it is a large file. It is worth checking you have followed it to the letter or it will not run very well.

The idle bleed screws allow in air past the butterfly. If air is already entering from somewhere you will not be able to close it down (i.e. alter the mixture of air and fuel to include more fuel and less air) by screwing them in.
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Unread 08-13-2014, 08:00 PM   #6
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Darn, Marshal beat me to it!!!

However the procedure in the manual is different. Try both and see what works.

The accelerator pump plunger needs to be up, not down, as it plunges DOWN to shoot the fuel out when you goose the throttle. Fine adjustment of the relationship between throttle and plunger through the linkages and screw on the arm at the pump dictates when the fuel is pumped in.

The metering rods are drawn UP by the throttle to unblock the passages and increase main jet flow. Again the relationship needs to be right, and it is possible to get the fiddly mechanism to sit too low and not get the extra fuel flow you need.

These two adjustments can dictate how well it runs above a fast idle.

Below that it is the idle tubes and bleed screws and the condition of the throttle shaft and butterfly and small vacuum leaks that can ruin the idle.


Stick with it, you are not far off getting it running. I have just installed a 34 year old BBD on Gladys to replace the Toyota carb and it all came flooding back, the fiiddliness.
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Unread 08-13-2014, 08:03 PM   #7
Marshal
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Lol, I didn't have the benefit of the manual. So I learned to adjust it without tools using trial and error. Chances are the book is more precise, but it's not impossible to get where you need to be without it.
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Unread 08-13-2014, 08:48 PM   #8
illinicj
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I adjusted the metering pins and the accelerator pump on the bench per the instructions in the rebuild kit. I'm positive I set them correctly per those instructions... Yours are very different. I'll have to look into that.

I really think the dripping fuel is a big part of my problem. Can't figure out why it's dripping. Should be steady flow.
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Unread 08-13-2014, 10:09 PM   #9
Marshal
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That had me wondering too. What did you use to clean the carburetor? Was it carb cleaner in a spray can, or did you get the gallon bucket with the dip basket? I asked because I've discovered the spray can cleaner just evaporates before it has a chance to get in there and really dissolve the gunk blocking those ports. Especially the finer ones. And you have to let it sit in the dip at least 30 minutes to get the desired effect.
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Unread 08-13-2014, 10:17 PM   #10
illinicj
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Both! I did a pre clean with the can and a rag, then soaked at least an hour in the gallon of carb dip. The venturis got rooted out with a wire (looked clean to start anyway), sprayed thru thoroughly, and soaked overnight in the bucket. Then sprayed out again after. Belts and suspenders!

This is driving me nuts. Makes me want to go buy the EFI kit I have always secretly wanted.
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Unread 08-14-2014, 12:00 AM   #11
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The dripping is certainly an issue, it will not idle well with blocked tubes. Usually you can get them to run at a fast idle by opening up the idle screw but they still die approaching traffic lights.
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Unread 08-14-2014, 12:08 AM   #12
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Unfortunately it sounds like the same story I just went thru....

With a rochester 2 jet.....bad idle,stumble, running rich.

I rebuilt the carb, cleaned it etc.....ordered a new float, new jets, new idle screws etc...much more than the normal rebuilds I do, usually no new jets, no new float and no new idle screws.

Put it back together like I have many times before on different model carbs......very minimal changes after rebuild in how it ran, tried a few different jet sizes, pulled out my bag of tricks on bending and adjusting linkages,pump shots etc.....no luck....also had to have the choke approx 75 percent closed to get any driveability out of it.

So I tore it down, repeated check everything very well, float levels gasket surfaces etc......no luck, stayed the same as before.

So I tore it down and started really looking at it.......accell pump well was worn, looked in thru the jet holes and noticed irregularities, inside the idle screw areas were a little funny......


I can to the sad facts that like many others who have had the same problems.......the new fuels have eaten away areas of my carb, the new fuels are very corrosive and bad for aluminum, certain castings much more than others.....some have minimal problems, some have big problems such as grey sludge at the bottom of the float bowls where the fuel is actually dissolving the metal.

Especially where any friction is involved, such as the accell pump well and where erosion wear is involved such as the idle jet passages.


Questioning my skills as this was the first 2 jet I have rebuilt, not my first carb, just first of this type......I did lots of internet reading and realized it might be a case of aluminum parts dissolving in the new fuels as experianced by many.

I ordered a rebuilt carb as I was ready to see if maybe I had some faulty parts in the engine,bad distributor etc and to see if a different carb made a difference.

It did....ran as close to perfect as a 50 year old engine can....steady idle,smooth accell,no dead spots or stumbles, not rich at all......idle screws worked as they should....

I know it is a ticking clock on the new carb untill the newer fuels do it in, but if I get as much service life as the last one since the new fuels were introduced, I will be happy.

Upon further research, I found people fixing the old ones with wear by bushing out the pump well for the accell pump and reprofiling the idle screws etc.

I did not feel like making a experiment out of learning new carb saving tactics, I did save the original carb as I might do this in the future, but there are passages inside that wear, that are hard to get to and will require drilling out caps and passages that have never been drilled and adding new caps....possibly filling in and redrilling passages etc.

I am very glad I opted for a new carb......might not be your situation, without hearing and seeing it for myself I could not tell you for sure.

I had, minimal changes with idle screw adjustements, a weak dribbely pump shot, hesitation,flat spots, poor idle, rich condition........all from what I found to be erosion of the aluminum casting.

Like I stated before, not all castings seem to be as prone to this as some are.......not up on chemistry make up of different aluminum formulas, who uses those different formulas in their carbs and what new chemicals in fuels might attack those particular aluminums.

But there are many many cases of it doing just that in different degrees ......it eats old formula rubber hoses etc, from cars to weed eaters, new gas lines and hoses have been altered to withstand this....some are now lined, some are of a different chemical make up.

So before I sent my old eaten up one out for a pro rebuild and spent more money on it, I opted for a different rebuilt carb...no regrets at all.
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Unread 08-14-2014, 05:22 AM   #13
Mike Romain
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Something fundamentally wrong with that carb. My first guess is the vacuum piston setting. This is the high speed jet setting. I am thinking you have it too rich so it is feeding at idle. Did you check the gap for the vacuum piston? Factory should be 035. I run mine a little lean at 042. Full lean is 050. Full rich is 025. The larger the gap, the deeper the needles go into the jets so the leaner it runs.

Other than that, the 2 small ball bearings come to mind. They are different sizes and have to be in the correct place.

If worst comes to worst, national carb sells a remanned BBD unit for $160.00 that quite a few folks have tried recently and been happy with. Although one gent got a real bad yfa from them. They did cover the bad one under their lifetime warranty, said they don't know how it got out the door.
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Unread 08-14-2014, 06:46 AM   #14
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You are chasing your tail fiddling with the carb until you hunt down that vacuum leak. 13" is way too low.

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Unread 08-14-2014, 09:16 AM   #15
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Did anyone check the throttle shaft yet to see if it's worn?
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