Cannot get the idle to specs !

Discussion in 'Carter' started by kindacool, May 8, 2006.

  1. kindacool

    kindacool Registered Looser

    Hi there,

    have a 1956 Buick Special with the factory 2bbl CARTER carb. Bought the carb rebuilt and put it on for the one that came with the car. The main problem remained: I can not get her down to factory spec idle of 450. Meanwhile replaced everything in regards of vacuum (carb base gasket, manifold gaskets, manifold fitting for Powerbrake) but that did not solve the problem. She runs good at 600, when you set her to 500 he starts to stumble heavily and below that instantly stalls.
    Also have the feeling that when I try on the idle screws @ 500 that the right bank responds to adjustment very good but left one does not except when you turn it all the way in (stall). Was the same with the old carb.
    When stalled and restarted she fires right up and is alive on the spot (so, I do not think that I have a mechanical problem with the engine itself).
    Any idea around here ?

    Thanks for any ideas
    Kindacool
     
  2. kwanderi

    kwanderi Keefer

    my guess would you still have dirt plugging the carbs internal passages.

    When idle mixture do not respond, its either dirt or a vacume leak.
     
  3. carbking

    carbking carburetion specialist

    An interesting comment in your statement that both the old and the rebuilt carb have the same idle adjustment problem (on one side). This could mean that the carburetor is not the culprit. Have you tried doing a compression test?

    Assuming good compression and ignition, then I would agree with Keith on either a vacuum leak or stopped up passages. However, often when a component is replaced to fix a condition, and the condition does not change; the diagnosis, not the component was faulty (no offense meant).

    Jon.
     
  4. kindacool

    kindacool Registered Looser

    Thanks everybody for the input so far !

    I have the carb disassembled already for re-cleaning, but carbking is right that the diagnosis might be wrong (which came to my mind, when I replaced the carb, too).
    Three things I will try:
    1. Test my tachometer on another car that has a tach-unit in the dash (talking 'bout looking for the problem beyond the usual path... :grin: )
    2. When the carb is back together again, retry to adjust it.
    3. (also known as "Plan B") Look for somebody who has the equipment to do a compression test.

    Is it very likely that compression is the problem ? When warm she starts on the spot (the cranking motor barely has to turn)

    Best regards and thanks again
    Kindacool
     
  5. RAbarrett

    RAbarrett Well-Known Member

    Something to try is this: with the engine idling, try spraying carb cleaner down the carb, on both sides. I suspect that the problem may not be the carb since a new unit did the same thing. It is possible that the same carb may be installed after cleaning, and have an issue, but it would be unusual for a different carb to duplicate the problem perfectly, if it is the carb. It is very likely that a leaking intake gasket could cause the problem, and it is very possible that a timing issue may cause the problem. If the timing is advanced, either by adjustment, or if an advance weight were sticking, it would require a lower than normal adjustment, causing the stall. Something else to consider as well is that the engine is not intended to idle in park at that speed, and if the idle is being set that way, the trans in drive would likely cause the engine idle to drop to below 375, which is most likely too low for a signal to the carb fuel jetting. Let us know... Ray
     
  6. kindacool

    kindacool Registered Looser

    Thanks RAbarrett,

    I will consider/try all your suggestions. I guess idle adjustment is to be made with Dynaflow in "N", is it not ?
    The problem I have with 100% correct timing adjustment is -of course-, that the manual requires 350rpm maximum for that to prevent advance weight action... no way to go that deep for me ! So there is a graph in the manual that shows timing in relation to rpm and I just did the timing adjustment at 800 (9 before U.D.C. then, I think)

    I will put the carb together over the weekend and do some testing on base of all your suggestions !

    Oh, by the way, vacuum fitting for the brake booster is mounted in the branch for the left cylinder-bank. Provided that it still creates a vacuum leak - would that affect idel adjustment for the left bank only either ???

    Thanks a lot so far !!!

    Best regards
    Kindacool
     
  7. RAbarrett

    RAbarrett Well-Known Member

    If the brake booster leaks, it is VERY likely to affect the adjustments for that bank. Answer me this, does the engine run rough AT ALL? If so, it might provide a clue to the source. If it does, knowing which cylinders contribute the most to the rough running will help me help you. Something else to consider as well is that you are making assumptions regarding the timing advance/rpm on the table. If, for some reason, the distributor is advancing the timing differently than the factory indicates, it is likely that the initial timing will be off. By the way, if that is your ride in the picture, that's not kinda cool. That's VERY cool. I have considered the possibility of having a mid fifties Buick Roadmaster to be something really cool. Ray
     
  8. kindacool

    kindacool Registered Looser

    Hi RAbarrett,

    I will -hopefully- get a new T-fitting for the manifold (for Booster vacuum) tomorrow and then will know if I found the problem.
    I would say that the engine runs rough in general, yes, at least slightly. Tell me, how do I find the cylinders which are troublemakers ? Bank-wise spoken it is the left bank -surprise!- I would say: The exhaust sound indicates the same and is rather irregular compared to the right side.

    And yes, that is our ride (part of the family I would say, all in Tahiti Coral, named "Piggy" by my girls for some reason... :grin: ). Would be even more cool if she would learn to behave soon:rant:!
    But thank you, she really is a dish, is she not ?

    Thanks again for all so far.

    Kind regards
    Kindacool
     

    Attached Files:

  9. RAbarrett

    RAbarrett Well-Known Member

    Something I always used when I needed to do some troubleshooting, before I had a scope was to pull off one spark plug wire at a time, while the engine idled. Pulling off of the cap instead of the plug will prevent your getting shocked. If the cylinder drops off noticably, note that fact, as well as the ones responding weakly. The ones responding weakly are the ones you need to attack. This attack may yield some strange results, but just let me know what you find, and we'll go from there. And, yes, that is quite a dish. I like it! Very cool! Ray
     
  10. RAbarrett

    RAbarrett Well-Known Member

    Just an additional note here: I have always enjoyed the spicier women more than the boring ones. Ray
     
  11. kindacool

    kindacool Registered Looser

    Hi Ray,

    you are right - I also like the spicier ones better! But frankly spoken, when you cannot get the spicy ones going, you will soon find them in the category "boring", too, will you not? :Brow:

    Did not have much time over the weekend (mother's day on Sunday), but at least managed to install the carb again. Found out that I obviously did something wrong during adjustment - after half an hour of idling, the choke valve still refused to open completely :af: . Also the starter keeps being engaged when engine does not start and you take the foot off the accelerator. But I did some tests with the idle cam manually set on hot. Replaced the distributor cap once more due to the installed one having some play and started to pull of wires at the cap. Started with wire of cylinder no 6 - when I had it out, the little brass contact that is clipped onto it remained in the cap... :ball:
    So, I made me some new wires yesterday installed them, started her up, set the idle preliminarily to a veeery smoooth 650rpm (adjusted with Dynaflow in "D" - and brakes applied, of course) and left her alone to have some coffee with the family...
    I have the feeling that everything I did so far contributed its bit to an improved idle, but still 450rpm is not possible (probably never will be due to the engine being somewhat worn), but I would like to get her down to 500 at least to soothe out the kick that is created when shifting into D,L or R.
    So, I am gonna play that wire-pulling-game you advised me of but first will go over ignition once again as rattling at the distributor cap had some effect on the idle in regards of making it stumble.

    Best regards so far
    Kindacool
     
  12. kindacool

    kindacool Registered Looser

    Hi Ray,

    so, I have checked the ignition again and replaced condenser, points and rotor and adjusted everything to specs. (Have to correct the timing though as it is on 7,5 sharp now - must have taken the wrong mark...).
    The result was nilpointnothing - still bad idling. I set her to 600 where she ran okay and accelerated the engine, but she stalled when the high speed system should cut in. On the third attempt she fired at me through the air horn and I decided the carb to be the problem ! So, I rebuilt the original carb and put it on, et voila: Most of the problems are gone. Good reaction on both idle mixture screws, good starting, idle can be set as low as 500-520 without stalling. Thus, I guess you will only get a properly rebuilt carb, when you do it yourself (the other one was bought readily rebuilt).

    Last thing I consider to be a problem is the choke. After half an hour of idling or so the choke valve will not fully open. Problem is the choke pipe I guess, which cannot be fastened at the carb in the intended manner, as the thread is gone on the choke housing - I will think of something...
    How is this pipe connected to the exhaust manifold ? It just seems to be stuck in a bigger type of pipe on my Buick and can be pulled out easily (if it has not fallen out by itself already...)

    Best regards
    Kindacool
     
  13. RAbarrett

    RAbarrett Well-Known Member

    I haven't heard from you in a while. Good to have you back. It is very possible to have a rebuilt give problems, especially since they typically rebuild in groups. With respect to the choke, it is very likely that the threads are gone, and this will limit the heat the coil gets, limiting the warm up. It is also very lilely that the air entering the choke coil is heated from more than one spot, and when the air cleaner is off, one or more of these heat sources is eliminated. Is this choke adjustable? Usually, the entire housing rotates, or the linkage may be bent to allow adjustability. It is also very likely after some fifty yeats that the linkage is loose, creating its share of problems as well. When you adjust the idle mixture, providing the smoothness of the idle, do you use a tach? Set the idle close first, then adjust the idle mixture. It should be carefully set to maximum idle speed, with each screw, then adjust the speed. Can you still get good fuel for Miss Piggy? Fuel has changed so drastically, especially with the advent of fuel injection, that it may be part of the problem. Are the points adjusted using a dwell meter, which is the most accurate method? Is the timing steady where you set it? I know that these are a lot of questions, but knowing the answers will help. Let me know... Ray
     
  14. kindacool

    kindacool Registered Looser

    Hi Ray,

    of course, I was offline rebuilding my carb... :laugh:
    Well, it seems as if the rebuilt carb was in storage for a long time before I bought it. The overall condition is worse than you would assume, seeing it from the outside (even the throttle valves show some rust now...) - but as the bottom line I would assume that my old lady just wanted her original carb back. You know how old people are with things they have become used to. :Smarty:
    Yes, the choke is adjustable, i.e. you can adjust the spring tension by turning the choke cap. I am gonna try to get the stove pipe connected to the choke somehow and if that fails I will play with the choke adjustment. Probably will not need a fully closed choke valve anyway, as during summer an only partially closed choke might be sufficient.
    The linkage is okay.

    Yes, I use a tach for setting the idle. Unfortunately it is a 4-cylinder tach, so you have to divide the reading by 2 which diminishes accuracy. What do you mean by "set the idle close first" ?
    As for the fuel, I worked for an oil company in Germany. Back then it was a known fact that fuel quality in the US was worse than generally assumed. German fuel was said to be pretty good and way better than legal stipulations required. I use unleaded premium (ROZ 95) with a lead substitute. It is even possible to get ROZ 98 and also ROZ 100 premium here in Germany, but as that is priced like you would not believe, for normal use I would like to stick to the ROZ 95 premium. (But trying out adjustment on half a tank of ROZ 100 fuel sounds very intriguing... :Brow: )

    I adjusted the points by the means of a blade feeler gauge, which I have done on older cars many times before, so I have some experience on how a correct adjustment should feel like. Gap is adjusted to slightly below 0.16" resulting in a gap opening for 31 cam angle. Timing mark is steady as a rock @ 7,5 (which is different from before).

    Best regards
    Kindacool
     
  15. kindacool

    kindacool Registered Looser

    Hi Ray,

    I did a couple of trips now and except that I will have to lean out the choke a bit I am almost satisfied (idle @ 500). I do not thing I will rattle anything about carb or ignition before the end of the season...

    There is only one thing that is peculiar about this car (independent of the carb I use): Everybody I told this was going "Yah, sure... hahaha" but I have tried to duplicate this problem several times and it happens almost on every attempt:
    The engine stalls when you try to make RH 90 turns out of a downhill movement. Sounds strange I know, but that's how it is: Only RH turns and when going downhill before making the turn, the engine stalls everytime. The byroad to my garage is downhill, the lane to my garage is a sharp 90 to the right and the cars goes into a uphill motion out of the turn - engine stalls in 100% of the attempts, I just cannot enter the garage without stalling the engine...

    Any idea ? (except going down the byroad in reverse and enter the garage in a LH turn, that is! :laugh: )

    Best regards
    Kindacool
     

    Attached Files:

  16. RAbarrett

    RAbarrett Well-Known Member

    Every picture I see of this Buick makes me envious. She is simply gorgeous. With respect to the questions, it is VERY likely that a misadjusted float in the carb, Or a "heavy" float can cause stalling in turns. The problem is due to the fuel in the float either exposing a normally submerged protion of the carb, or fuel "spilling" into the air stream instead of being controlled by the normal jets and passages. The heavy float can be the result of fuel saturating the float material, and the unit now does not sit in the normal position in the bowl, causing high fuel levels. Low fuel levels can cause the engine to stumble on acceleration, stalling, etc. When I made the comment regarding the setting of the idle close to specs, it is necessary to set the throttle plates in the correct position with respect to the internal passages in the carb. If the throttle is not in the correct position, it is possible to have a hesitation on acceleration, or rich mixtures when setting them. The idea when setting the mixtures is to be very close to correct with the idle speed, then set the mixture and readjust the speed. Back and forth will assure you consistent engine performance, and maximum economy. Try this. If the desired idle speed is, say 500 rpm in neutral, set the idle speed there. Then, carefully adjust the idle mixture screws for maximum idle speed. Then readjust the idle speed again, for 500 rpm, and readjust the mixture screws for maximum. The idea is to have both conditions occur at the same time, allowing for accurate adjustments. My experience now allows me to do the job in about 6 minutes, but without the experience, it may take a little longer. Accuracy is the key here, and it will likely result in some surprisingly smooth performance. As I recall, idle speeds should be set in gear with an automatic, so be careful with the throttle when setting these speeds. One more thing. If the idle speed should be set in drive, fine, but your idle mixture settings should be set in neutral or park. This will allow the tach to give you its maximum variance, making the readings more consistent. Let me know... Ray
     
  17. kindacool

    kindacool Registered Looser

    Hi Ray and everybody else,

    after forcing myself to forget about the problem for some time, being on vacation and attending some car shows, I decided to take another attempt to tackle this.
    Bought me a compression tester and a vacuum gauge (still to be delivered)... Ha!

    So, due to lack of time I decided to remove the spark plugs and do a compression test on the cold engine.

    Observation No 1:
    All the spark plug's electrodes are dull and black and sooty except # 2 and 3, which are light grey. As I understand that means for the black ones that mixture is too rich and for ##2 and 3 that mixture is too lean ?
    I mean is it possible that I am dumb enough to install only 2 out of 8 spark plug caps properly ?

    Observation No 2:
    Compression: Well, as I said, I did the test on the cold engine. I performed two runs with 2-3 takes on each cylinder. On the first run, #3 had 130psi and #2 140psi and all the others climaxed at 120psi except #5 which only delivered 110-115psi. All of them had the pointer jumping up to 100 or over on the first stroke and required maximum 3 strokes to deliver the final result. On the second run, all cylinders came out with 120 except #2 with 125 psi and #8 with 115. I guess, doing this on the cold engine does not make sense, or does this allow any conclusions already ? (Manual requires 160psi minimum for the Dynaflow Specials, but that is for the hot engine, as I assume.)

    Observation No 3:
    On both carburetors I tried, after some time of cranking with the ignition disabled, they, of course, were soaked with fuel on the inside after some time. Fuel started leaking through the throttle shaft bearings on both sides on both carbs. Is that acceptable up to a certain extent or might that be the key to my problem ?

    Thanks for letting me know what you think...

    Best regards
     
  18. carbking

    carbking carburetion specialist

    Cool - regarding observation number 3:

    If the throttle plates are completely closed (not a good idea); fuel from the main discharge nozzles (engine not running) is going to fall from the discharges nozzles on top of the closed throttle plates, and exit along the edge of the throttle shafts. If you were attempting to run the car with the throttle plates completely closed, chances are you would experience an erratic idle and a hesitation (possibly severe) when accelerating from a stop sign.

    The compression seems low to me, but will defer this issue to those more familiar with this particular engine than I.

    Jon.
     
  19. kindacool

    kindacool Registered Looser

    Hi carbking,

    thanks for your valued feedback. I will check, whether my attempts to bring the idle down made me fully close the throttle. :rolleyes:

    Also, after some time-out on the problem, I realized another thing that I had completely overlooked: When this car came to Germany in 1981, German DOT obviously required that a closed crankshaft ventilation is installed. The previous owner therefore removed both oil-filler breathers and installed caps with nozzles, ran a hose from the left one into the air cleaner and a hose from the right one to a nozzle he welded into the intake manifold...
    There we are I guess: Would you agree that doing the latter will ruin manifold vacuum ?
    Will block this nozzle tonight and see if there is any difference...

    Regarding low compression: I guess it really does not make sense to test on the cold engine. It had been sitting for some time and I would guess the lack of a proper oil film between piston rings and cylinder walls will prevent proper compression. At least, compression on all eight is somewhat the same...

    Best regards
    Kindacool
     
  20. kindacool

    kindacool Registered Looser

    Well, now I blocked this stupid additional ventilation opening into the intake manifold, set the carb to the initial setting and had her idling a bit. From the sound of the exhaust, firing is much smoother and even now, especially on the left bank.
    After some time (water temp gauge crawling near "N"), I tried turning in the right idle mixture screw. No stall until I had the screw seated, so I also tried the second one and she was still idling with both screws seated. Exhaust gas being very rich. I stalled her by backing off the idle set screw and with the lack of vacuum within an instant there formed a foggy ball of "mixture-mist" over the air horn... I blew it away and looked into the air horn and apparently there was a flow of this foggy stuff into the air horn coming from 2 positions over pump jet level. When you look into the air horn, the flows were coming mainly out of the 4 and also a out of the 8 o' clock corners of the air horn.

    What is that again :shock: ? This problem is new to me :Do No: . She always responded to the idle mixture screws and never ran that rich...

    Seems to be cursed or is there any other explanation ?
    What are the odds that the old lady just hates me and tries to make me go into a fit ? :blast:

    Thanks for any feedback

    Best regards
    Kindacool
     

Share This Page