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Unread 01-19-2002, 08:37 PM   #1
Billy Badass
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The JKB2 BDD Carb Mod

Well do to the number of resposes I recieved from you guys, (and gals) asking for instructions on how to do the mod, I've put together this post.
I have tried the so call mod of drilling out the idle fuel pick up tubes to .032". But the results were dicouraging. It ran better but did not stop the tubes from cloging up. So I checked out the tickness of the tubes and ran some numbers through my head. The problem with doing a modification like this from scratch is that if you make the tubes to big it won't idel at all. I started by extracting the particles that eluded my fuel filter to clog up these tube, then measured their size. I found out that the biggest particle I measured was onlt .037". So I decided to go just a tad over the size of the particles, .040" Re installed the tubes and it actually ran better than I expected, I recieved more bottom end and quicker trottle response. Here are step by step instructions. I'm sorry I don't have any pictures of the procedure, it didn't cross my mind.

Step 1: Open Hood. In case you don't know.

Step 2: Remove the choke plate from the top of the carborator. There will be two screws holding it on.

Step 3: Then you will have to remove the choke plate mounting bar, this will be held on with one screw at the very end of it, you then gently slide it out and set it to the side.

Step 4: There will be two screws called cluster screws. They will be on top of the venturi cluster. Remove both of them and set them to the side.

Step 5: At this point you can reach down with two fingers and lift out the venturi cluster. You will not have to buy new gaskets or use any sealer.

Step 6: Now you can disassemble the venturi cluster. Gently lift out idle fuel pick up tubes from the venturi cluster. The are the flat plate on top of the venturi cluster that the cluster screws screwed into. When you lift them out you will a plate attached to two copper tube. The are the little buggers that caused you so much hell.

Step 7: It is a good idea to go ahead and clean all these parts while they are out. Start with the venturi cluster, spray it with carb cleaner or brake cleaner. If you have it run a piece of fine wire down the small holes in the end of the venturi. Clean the idle fuel pick up tubes the same way.

Step 8: Get a #60 drill bit from radio shack, it was the only place that I could find one this small. It will be .040" You don't want to use a power drill to drill the tubes out you can actually wallor out the holes two much. The part that you will be drilling is only about an 1/8" long, it will be at the very end of the tubes where the size of the tubes reduces. This is what you will drill out. You will be able to purchase a small hand drill for a few of bucks from radio shack.

Step 9: Insert the drill bit into the very end of the tubes and begin to trn it slowly it will give you a little trouble trying to start it, but as soon as you get it started it will glide easly through the soft metal, it takes about 30 seconds a tube. I had to tighten my drill with pliers to keep the drill bit from slipping in the drill. you will see fine pieces of the metal come off in strands and the then it will push through the reduced area and into the wider part of the tube. Then thats it.

Step 10: Clean thoughly with a cleaner to make sure that there are no metal particles left in the tubes and then reassemble in the oppisate order that you took the parts apart (step 2 to 6 in reverse).

Step 11: Now the idle mixture screw will have to be backed of around two turns, you may have to play with it a little bit until you get it to idle right, mine is at two and a quarter turns while some have used 2 1/2 turns. It just depends on your specific carb and the shape of your engine. Now you will relish in the new power of your bottom end, the new life that you have breathed into your tired old engine. This modification will increase bottom end and trotle response, it will idle again and not die at every stop light, if it dose not then you most likely has a choke problem, and this will barely help you. I hope you like it keep me posted on how this turns out. remember this modification and it's results are from my own personal experiences, and my friends. But I have not gotten any bad results yet, and my jeep runs like a dream with 100,000 miles on it. And you will never have the problen of the these tubes clogging up again.

Later!

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88' YJ 3" body, 32x11.50 ProComp Mud Terrain. JKBII Carb Mod. Nutter Bypass and a new ignition. White Faced Gauges with blue backlighting. Sone to come 4.10 gears and lockers.
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Unread 01-30-2002, 07:46 PM   #2
clint_black_jeep
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Billy- tried this over the weekend and definitely fixed my problem...looks like I can put off that 4.0-into-4.2 swap!
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'85 CJ-7, bone stock exc. 2" shackles & Skyjackers. Engine is 258 (for now). Nutter bypass.

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Unread 02-03-2002, 09:07 PM   #3
jeepster18_88
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I am planning to try to rebuild my carb on my '85 cj7. What is this mod supposed to fix exactly and are there any side effects on a jeep that's to be driven daily? Will this effect gas mileage or top end performance? Thanks for any help.

P.S. Does anyone know of a site telling how to rebuild the carb?
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Unread 02-04-2002, 03:00 PM   #4
Billy Badass
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It fixs the idle problem that plaques the BBD carborator, it keeps the idle tubes from cloging up so that it won't idle and stumble when you push the gas. It makes your jeep idle and run better. All you have to do is turn back the idle mixture screw to make it idle perfect after you do the mod, I actually got better gas miliage, than I did before because I didn't have to floor it or keep the rpm's up when I came to a stop and tried to take off. It will not affect driveability, at all and I just had my emmisions done out here and passed better than it did last year. It will not affect top end except for giving you another 750 rpm's higher in your power band. So I hope that it all works out for you, you will be happy with the results, it will breath new life into your jeep. I promise.

Later.
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"Nothing like the feeling of braking something important and exspensive"

88' YJ 3" body, 32x11.50 ProComp Mud Terrain. JKBII Carb Mod. Nutter Bypass and a new ignition. White Faced Gauges with blue backlighting. Sone to come 4.10 gears and lockers.
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Unread 02-04-2002, 07:48 PM   #5
jeepster18_88
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Thanks for the help. Do you have any suggestions on mods for power? I don't know anything about car carb but I have worked on 4-wheelers. Should I change the jets(or can I) and if so what size should I change to for more midrange power. Thanks again.
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Unread 02-05-2002, 12:06 AM   #6
Billy Badass
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There are not realy a lot of mods for this carb which might be a good thing. These carbs suck. If you got the money go with a weber carb, around 400 bucks. It will give you up to 20% more power in the 38/38 version, and about the same gas milliage. You can pick up a cam kit for about a hundred bucks, I recomend Crowers Beast Cam They work great with the torquey 4.2 Liter. You can always get some roller rockers. Put in some rhodes lifter. So you can run a big cam. The rhodes lifter will allow a big cam that normaly operates at say 2500rpm to 6500rpm to act as a roller cam and run from idle to 6500rpm with the same cam and they are under a bill. You can always do a 4.0 liter head swap. Depending on where you live it should cost you now more than 300 buck in cluding the machining. Or as little as a hundred for everything. Put some headers on it with a nice exhaust system and put a new ignition on it. Basicly you can pump out over 200hp for a fairly chaep amound without going to fuel injection. And if you do it later, even more power. Just remember when you can cut down on even a little friction you will get more HP. Get a Tornado, it looks stuped but it realy dose work, you get a better mixture and a better burn and better gas miliage. I also believe that Rimmer has a super charger for the 4.2 liter but don't hold me to it. I would do the 4.0 head swap it is good for 40 hp, and if you have it ported and polished it is even better. Try the Splitfire Platnium +4 for a little bit more juice. There are actualy a lot of upgrades you just have to look carefuly. I would rather do a 4.0 motor swap, and stroke it to a 4.7 liter and have the fuel injection, and you can find the engines complete for about 800 buck with computer and wiring harness. Well whatever you do write me back and tell me how it worked out for you.

Later;
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"Nothing like the feeling of braking something important and exspensive"

88' YJ 3" body, 32x11.50 ProComp Mud Terrain. JKBII Carb Mod. Nutter Bypass and a new ignition. White Faced Gauges with blue backlighting. Sone to come 4.10 gears and lockers.
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Unread 02-05-2002, 12:41 AM   #7
jeepster18_88
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Thanks for all the ideas. I've been considering some but right now I'm trying to find a new job so money is not only a problem but completely and insanely out of the question for now. I thought about the Tornado but it will be useless if I buy the Weber later on. I have some Platinum Plugs but I've heard that they won't do well if your engine burns any oil. I think mine might but I'm not ready to rebuild it. I was also told that changing a cam in a motor with high (over 50 to 60k) could do serious damage and probably not last long. I'm most likely going to install a juicebox and headers as soon as I can find a job. (The economy is pretty screwed up right now though.) Engine mods aren't my top priority right now, I'm just trying to help it get on down the road a little better. Thanks

P.S. My BBD hasn't showed any problem at off camber angles yet. Even when I parked it with one tire in the air and let it idle for a minute. It nearly dies when I hit the washboard bumps on the dirt road that I live on though. Stupid carburetors. HAHAHA
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Unread 02-05-2002, 08:15 PM   #8
Billy Badass
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Who ever told you that it would not work with the weber was an idiot. It will work better with a weber. It just swirls the sir it makes any carb or fuel injection run better. It swirls the air like a super charger, but dose not compress it. And any one who told you that a cam would work in the engine you described was a moron. It will work get, I know I go to Wyotech. They are my life. Platniums will work even if your engine burns oil. Just use common sense. No nitrious on a high miliage engine just because the clearances are worn out.
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"Nothing like the feeling of braking something important and exspensive"

88' YJ 3" body, 32x11.50 ProComp Mud Terrain. JKBII Carb Mod. Nutter Bypass and a new ignition. White Faced Gauges with blue backlighting. Sone to come 4.10 gears and lockers.
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Unread 02-06-2002, 08:07 PM   #9
jeepster18_88
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So your saying that the Weber will work with the stock air cleaner assembly? If not then how could I use the big round tornado in the small square air cleaner that comes with the Weber. That was what I meant by useless. I would rather use the stock air cleaner with a Weber, tornado, and K&N filter. Would this work? Thanks.
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Unread 02-09-2002, 02:46 AM   #10
Billy Badass
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Oh ok now i see what you were say'in, my bad. The assembly you suggested would work but I forget about the little dink air cleaner for the webers. My mistake. In that case forget what I said. Just slap on a weber if you could manage to fit a tornado in there go for but it is'nt likely. Once see i forget about the small air cleaner because I want to put a snorkle on mine the tornado will fit in the snokle. I have my nutter bypass set up on switches right now so I don't have to worry about screwing with the visual inspection. So as soon as I flip two switches I complete the nutter bypass. So that way they emisions nazis can't nail me. I you need any advice just email me and I will help all I can. I just installed a body lift today and slaped some 32" under it on the stock rim so I can still stuff them into the finder wells. This is my second jeep so I just now starting to work one it. Future plans. Dana 44 swap. 36.5" tires spring over and a four and a half inch suspension lift. And take the cheesy body lift off, just put it one to romp through the snow. Well tell me how everything work out and if you need any help just let me know.

Later.
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"Nothing like the feeling of braking something important and exspensive"

88' YJ 3" body, 32x11.50 ProComp Mud Terrain. JKBII Carb Mod. Nutter Bypass and a new ignition. White Faced Gauges with blue backlighting. Sone to come 4.10 gears and lockers.
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Unread 03-01-2002, 11:08 AM   #11
Billy Badass
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i
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"Nothing like the feeling of braking something important and exspensive"

88' YJ 3" body, 32x11.50 ProComp Mud Terrain. JKBII Carb Mod. Nutter Bypass and a new ignition. White Faced Gauges with blue backlighting. Sone to come 4.10 gears and lockers.
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