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Weber Carb K551 - Survey

3458 Views 15 Replies 1 Participant Last post by  gregcs
Hello Folks,

Many of you have already shared some of your experiences with the Weber Carb K551 and the 258 engine with me, however I am going to ask that anyone with the K551 Weber please reply. I have found that many of you are quick to help so I am hoping this will be the case with this quick survey as well. I greatly appreciate your help.


1) What is your idle speed with "no load" set at?
2) How many turns in is your Idle Speed screw after it makes contact with the throttle linkage? If it is more then 2 turns what does your idle drop to when set at 2 turns?
3) How many turns out is your Idle Mixture screw?
4) Did you have to install a idle jet that was different in size than the stock one? If so why?
5) What is your Choke Idle or High Idle set for?
6) While engines is running at High Idle (during choke)... when you tap the gas pedal to release choke does the RPM's drop all the way down to base idle or does it drop to an intermediate idle? (Ex. High Idle 1600, tap - drops to 1200, tap again - drops to base idle?)
7) Did you connect your EGR? If so did you connect it to the EGR Port on Weber?
8) Did you connect your Vacuum advance to Weber Ported vacuum or to Manifold Vacuum? and why?
9) Are you using the stock Distributor/Ignition or an HEI system or other?
10) What did you set your timing to? and at what RPM's? and did you set it with the Vacuum advance disconnected?
11) Do you have an automatic transmission or manual?
12) Did you install a fuel pressure regulator to help regulated the fuel pressure?
13) Do you have problems with the fuel draining back after the jeep has sit a day or two and you have the crank the engine for a short period to get gas back up to the carb to start? If so, how have you fixed this?
14) What gas mileage do you get?
15) What Tire size do you have? (just want to know this because of gas mileage)

Once again thank you for taking your time to help. Some of the questions you many not know the answer to without looking under the hood, checking, or doing a quick test... so once again I greatly, greatly appreciate you taking your time to check!!!!! If there are any questions you think should be added please let me know.

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Ok... here is my own answers and comments to the survey:

1) Currently at 520RPMs. Why? Weber told me to set it at 400 to 500. I think this is too low and this is one reason I started the survey.
2) Exactly 2 turns in after contact. Again Weber said not to turn it in more that 2 turns or I am exposing my progression port. At 2 turns I get 520RPMs
3) 2.25 turns out. Weber said make sure between 1.5 and 2.5.
4) I had to jump up 2 idle jet sizes to the 85. Why? Back to Weber saying not to turn idle speed screw in more than 2 turns. With the stock idle jet and set at exactly 2 turns in on the idle speed screw then my idle was only 400RPMs. Way to low to me.
5) I set it to 1500 if engine is warm. When engine is cold it goes to about 1300 and slowly increases until I take choke off.
6) When I had the choke original set at 1800RPMS I could tap the pedal and it would drop to about 1300 and then tap again and it would drop to base idle. Now that I have choke set to 1500 I tap the pedal once and it drops to base idle.
7) My EGR is not connected at this time. I plan to connect it to the Weber EGR Port.
8)Vacuum advance is currently connected to Weber Port. Why? Just followed insturctions.
9)Currently using stock distributor with Accel coil. Changing over to HEI soon.
10) 5BDTC at 1600RPMs with no vacuum advance connected.
11) Automatic
12) No... however looking to do this based on a couple of other Jeepers recommendations.
13) Yes after a day or more it takes quite a few turn overs to fire up engine due to gas draining back. Haven't fixed it yet.
14) I am not sure due to tire size and speedometer being off, but my best calculation is about 13.5MPG
15) 33x12.5 Tires

Thanks again for your time.

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OK Greg, here's my answers (at least the ones I know!)
1. App. 700
2. ? I didn't even bother to look. Just hooked up a tach and got the idle I wanted.
3. 3 1/2
4. No
5. App. 1600
6. Drops to base idle
7. No
8. Left it just as it was, manifold.
9. Stock
10. Manual
11. Napa regulator set at 2 1/2 lbs.
12. I think this may be an evaporation problem. Since I started parking in the garage, it is not a problem.
13. Who cares, can't do much about it anyway and I like the way it runs!
14. 33x12.50
Hope this helps.

Brad (from the 4 Wheeling center of the universe, 4 corners USA)
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Figured I better resond too...
1) 700 RPM
2) Set it and forgot it.
3) About 3 1/2, until the motor ran smooth w/no sudden shakes
4) No
5) Right about 1500 RPM
6) Falls right back to base idle
7) Not using the EGR
8) Vacuum advance connected to carb
9) Stock Dist/Ign (Going to Jacobs shortly to try it out)
10) 5 degrees/vac disconn
10) Manual tranny
11) Yes, have Balkamp fuel press reg at 2.5 lbs (thanks to Brad)
12) Yes, must go thru about 4 starts to get it to fire.
Planning on disconnecting the fuel return.
13) Was getting about 12, now I think it's slightly better, but, who cares...
When it runs outta gas I put more in....
14) 35 x 12.5

85 CJ8,258,Weber32/36,4" BDS lift,4.10,35"tires,f/r lockers
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This is for anyone reading this:

Thanks for the replies so far... Now I am going to test everyone's patience. Because Weber has made such a huge deal about not exceeding 2 turns in of the Idle Speed Screw... I am going to ask those who are "willing" to find out trully how many turns in their Idle Speed Screw is and if it is more than 2 turns in what is the idle speed when at 2 turns. I know, I know... you probably DO NOT want to mess with it, but I am trying to learn everything I can about how the Weber is actually being used as opposed to what Weber is saying needs to be done! All I can say is thank you for your time... I wish I could offer something for your time, but I can't other than thanks and I hope I will be able to help you with a question in the future when I get up to speed on things.

Thank you.

I know there are more Weber owners out there? Where are you?

I have one, but I am going to use your survey to review my setup for accuracy, I'll be glad to let you know what I find, but it will be a week or two, weather permitting. So far, I need to look at the Vacumn advance and the egr connections. For the record, I am using the HEI, no fuel pressure regulator. The other settings are a vague memory, plus, they may have changed when a mechanic buddy got this setup to pass the sniffer/emisions test for North Carolina. /wwwthreads_images/icons/wink.gif
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Hey Greg,
Well here is the deal with my Weber experience. I also have an 89 YJ w/ 258 auto trans. I was tired of the "cold start" performance of the BBD, but after the motor warmed up it ran pretty good with the stock carb. I decided to try the Weber K551, bought the kit from Leon Rosser for about $326. if I remember.
Got the kit a few days later and installed it. Took me most of the day because I also got rid of any useless vac lines, wiring and pulse air sys. I pretty much just took out the "rats nest" sitting on my engine, I can acually see the engine now! Well the install went pretty good, had to play around with the linkage a little and re-set the timing(already had HEI). Adjusted the carb to lean best setting and went for a little test ride. First off, I noticed the really LOUD air intake noise with the K&N that annoyed the hell out of me!Then the jeep fell flat on its face at anything over half throttle.... real bad hesitation and bog. As the engine warmed up it got a little better, but still very noticable(I couldnt even pull out into traffic)! Drove it around for a week hoping to "break it in" and try to adjust it more. Still no better after a week so I called Worldpac (Weber Redline). The guy on the tech line was really no help at all. He was pretty much just reading the instructions as he told me what to "try". He promised to send some jetting parts.....2 weeks later and no "next day air" parts I called him back. This time on the cell phone so I could tinker while he was on the line. I even took him for a ride while we were on the phone so he could here the "bog". Again he promised to send some parts and a Weber manual..... overnight. 2 weeks later after no parts in the mail, I called Leon Rosser and kind of demanded they take the carb back! After some talking with a few people they agreed to refund me! One girl I talked to said they were having "quite a few problems with the Webers"
To answer your questions the best I can remember...... My idle was set about 800 rpms out of gear and droped down to 600rpms in gear. Mixture setting was 2 - 2 1/2 turns out. Fast idle I set to 1500-1600 rpms, dont remember how it kicked down. I played with the timing quite a bit.....mostly because of the HEI. I just set it as advanced as possible so that it didnt "ping". I think that I am at 5-6 deg btdc at idle rpm, with vac advance plugged. With the Stock carb back on ,computer bypassed and HEI, it runs great when warm, but still has the "cold Start" Prob. No "bog" with the old stock carb....only with the new Weber. I May try a "pre-computer" BBD for a 1980 CJ-7 auto 258 or I may try EFI, prob The Howell TBI set-up.....$1000..Ouch.
Just so you Know, The tech reps at Worldpac(Weber) will try to tell you you have your timing is not set corectly and you have some sort of vac. leaks on your engine! Thats there way out of the phone call. Why did the old carb run fine with my vac leaks and timing way off I asked answer! I talked to a few people on this BB who had the same prob. Most everybody I talked to had some sort of "bog" prob and set up troubles!
Sorry for the long winded post but I thought you would like to know that your not the only one who has had probs with the Weber!
P.S.......Still waiting for those "overnight" parts....6 months later ;-).
If you need any more help, let me know.......Herbie

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You know, I keep hearing about people that have had bad experiences with the Weber, I can't for the life of me figure out why. It's the best improvement I've made to my CJ7 in the 14+ years I've owned it. I did find out why a couple people have had bogging problems, though, they used the wrong Weber, tried using the bigger one on a stock 258.

Brad (from the 4 Wheeling center of the universe, 4 corners USA)

Thanks for the reply. I am not really having bog down problems or anything indicating a problem other than not getting the RPM's required at 2 turns or less... as Weber says I need to do. The engine runs smooth, no hesitation, no surges, no sputtering (unless I run out of gas). If you have followed all my posts you will probably remember me saying the Weber Tech guy said that my idle needed to be 500. Just about everyone else online has it at 700 or better. I received another email from Bud at Weber and he said that it should be around 700. (MAN WHO DO YOU BELIEVE).

Herbie, I too have been told I must have a vacuum leak or timing problem. Everything has been checked and there are no vacuum leaks. All new hoses in the whole system. One suggestion is I have blow back or a valve leak. I will be trying to double check the compression test this weekend (weather permitting).

I finally recieved another email back from Bud at Weber. The only suggestions given until this last email from him was to look at the lean best idle instructions. I have done that a dozen times already!!! It doesn't change anything. Anyway, he has added a few suggestions this time that I am going to try. Also, another Jeeper sent me a note on how to check something else.

I will continue to follow up with the progress as time permits. Also I hope to get a few more survey results in.

Oh.. from what several other jeepers have told me you should have been able to get that Weber working great (if tech support would have been helpful). I think Weber has a great product when things are set correctly and when you receive the appropriate technical support. This is an example of how a good company can make itself look very, very bad.

Thanks again.

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I haven't counted mine as a "bad" experience just yet. My Jeep is driving much, much better than it was when I bought it a month or so ago... however, just a couple of small things could make this turn into bad... and one is not getting assistance in a fair amount of time. I am this |--| close to having mine working perfectly... just wish I could get Weber to quickly respond. Just one quick example: It took over 18 days to get a response back from my email that had something other than read the lean best idle sheet.

Thanks again for the replies. More to come as I have it.

One thing many people overlook is the very common problem of a leaking intake manifold gasket. No matter how many other leaks you find, it will still run terrible if this isn't fixed.

Brad (from the 4 Wheeling center of the universe, 4 corners USA)
Prior to starting all this I compeletely degreased the engine to help me spot any oil leaks, etc. I haven't had any oil leak from anywhere yet. <Crossing Fingers>

Let's say someone does have a leaking intake manifold gasket... how would they verify it is leaking?

I have sprayed carb cleaner all over the place while the engine is running to see if I have any hesitation or leaks, but no change in idle.

I bought mine from e-bay for $50 they said it had a bad throttle bushing .Turned out to be a leak at the fuel line hook up.Hooked that 32/36 on the clifford manifold with an HEI runs great have been fighting a holley for 12 years. I can't understand all the negitive comments ,best $50 I have spent on that jeep in the last 21 years


Would you mind filling out the survey since you have one???

I was just checking to see what posts I had made in the past and I thought I would give an update on this since things have changed.

There were a lot of things I did, but ultimately switching from the Standard Dist and the Accel coil (that was there when I bought it) to an HEI system made a huge difference. I was able to go back to the smaller IDLE jet and I was able to get the RPM's to 785 at 1 and 3/4 turns for the idle screw. So in my case the the coil/distributor system made a huge difference.

I can't say for sure I have everything perfect, because I still have some performance problems, but they are likely due to other things than the Weber.

Thanks.... just thought I would give a final update.

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