56 Buick Posted October 10, 2018 Share Posted October 10, 2018 Hi Touched briefly on these issues in another thread but i didnt want to hijack that thread so hence this new thread. The shop mnanual states that in order to set the ignition timing correctly then the idle needs to be reduced to 350rpm so the mechanical and vacuum advance are not operating. Now the car was idling around 700rpm. Beemon suggested the engine was running rich so I screwed back the idle mixture screws and i can get the idle to 650rpm but it runs rough. I tried pulling on the throttle linkage to pull the throttle back hard against the stop and it will go down to 500rpm where it stalls. As a result, I cant be certain the timing is set correctly albeit there is no pinging. Does anyone have any advice. I am thinking i will get a vacuum guage to see what that is reading. Thanks Drew Link to comment Share on other sites More sharing options...
Beemon Posted October 10, 2018 Share Posted October 10, 2018 You'll need a tachometer or vacuum gauge to set your idle just right. The shop manual says turn all the way in, then turn about 1 and 1/8-1/4 turns I believe for a base setting on the idle mixture screws. This will get you started. To drop your idle, though, you need to adjust your idle stop screw. What carb do you have? Link to comment Share on other sites More sharing options...
56 Buick Posted October 10, 2018 Author Share Posted October 10, 2018 The carb is the original 4 barrel Rochester. I have a tach on the timing light but i will need to borrow a vacuum guage. I am actually thinking there is an issue with the carb. I can turn the idle stop screw all the way out so it is not against the stop at all but the idle is still at 650rpm. This is also after screwing in the idle mixture screws. They are set at just under 1 full turn from all the way in as the engine was running rich at idle previously. Link to comment Share on other sites More sharing options...
JohnD1956 Posted October 10, 2018 Share Posted October 10, 2018 (edited) @56 BuickFirst, check to make sure that the fast idle cam is not in play due to that linkage hanging up. Then make sure the dash pot is not in play due to mis-adjustment. and then check to make sure the gas pedal linkage is free of obstructions and not mis-adjusted. If the engine idle screw is not back in play after all that, then start considering a carb rebuild as a possible need. Edited October 10, 2018 by JohnD1956 (see edit history) Link to comment Share on other sites More sharing options...
old-tank Posted October 10, 2018 Share Posted October 10, 2018 Be sure the rest of the ignition system is correct including a stable correct dwell (about 30 degrees) through all rpm ranges. Usually if you cannot reduce rpm without dying it indicates a vacuum leak...disconnect and plug all lines. One of mine refuses to idle down due to vacuum leak around worn throttle shaft. I start it cold, rotate off fast idle cam and put in D (parking brake on and wheels blocked and remember not to touch the throttle). 1 Link to comment Share on other sites More sharing options...
Daves1940Buick56S Posted October 10, 2018 Share Posted October 10, 2018 You can also static time it, guarantees no unwanted advancing if the mech/vac advances are in good nick. Cheers Dave 1 Link to comment Share on other sites More sharing options...
avgwarhawk Posted October 10, 2018 Share Posted October 10, 2018 (edited) 9 hours ago, 56 Buick said: The carb is the original 4 barrel Rochester. I have a tach on the timing light but i will need to borrow a vacuum guage. I am actually thinking there is an issue with the carb. I can turn the idle stop screw all the way out so it is not against the stop at all but the idle is still at 650rpm. This is also after screwing in the idle mixture screws. They are set at just under 1 full turn from all the way in as the engine was running rich at idle previously. Seems odd the idle mixture screws make no change when adjusted. Are the idles mixture screws in good shape? Edited October 10, 2018 by avgwarhawk (see edit history) Link to comment Share on other sites More sharing options...
1957buickjim Posted October 10, 2018 Share Posted October 10, 2018 I know in a 1957 Manual, they have a specific section in the proper steps in adjusting tuning your engine by adjusting everything in a certain sequence. Not sure if it is the same in the 56 shop manual, but it is in section 2-10 as to what to do, step by step. This is the link to 1957 Buick, but should be similar for 1956: https://www.hometownbuick.com/1957-buick-engine-tune-trouble-diagnosis/. Might be worth a shot.. Link to comment Share on other sites More sharing options...
56 Buick Posted October 12, 2018 Author Share Posted October 12, 2018 I got some work to do! Thanks everyone for all the good advice. I will post back when I resolve the issue. The answer may help soneone else in the future. 3 Link to comment Share on other sites More sharing options...
56 Buick Posted November 1, 2018 Author Share Posted November 1, 2018 Just an update but still work to do. Still cant get the engine to idle down. Checked there is no interference by the fast idle cam and the dash pot. I have replaced the plugs, distributor cap and rotor. I have put a pertronix electronic ignition in the distributor so no points. The vacuum guage connected to the inlet manifold provides a steady 18Hg of vacuum at idle and i set the idle mixture screws using the vacuum guage. Albeit one side does not really respond the same as the other - so there is possibly an issue there but that would not be affecting how low the idle will go. I ended up setting the distributor advance by sound and picking a position that gave a good even run noting that either side of that position the engine idle would begin to run irregularly. The only other thing to do now that i can think of is to look at the linkages to see if they are keeping the idle high. Link to comment Share on other sites More sharing options...
avgwarhawk Posted November 1, 2018 Share Posted November 1, 2018 (edited) The idle is 650 rpm? What is recommended in the manual? 425-450 rpm? What is the rpm in gear? If you were able to obtain 425-450 rpm, would the engine be happily running at that rpm? Edited November 1, 2018 by avgwarhawk (see edit history) Link to comment Share on other sites More sharing options...
Beemon Posted November 1, 2018 Share Posted November 1, 2018 Before you start playing with ignition timing, you need to verify ignition timing. What is it? 18 in Hg is too high for a 56 322, the idle vacuum should be 15-16, as reported by the factory. You're probably too far advanced. If one idle circuit does not respond the same as the other, then your idle circuit on that side of the engine is plugged. You can try using compressed air on the affected side. When was the last time the carb was cleaned thoroughly? 1 Link to comment Share on other sites More sharing options...
old-tank Posted November 1, 2018 Share Posted November 1, 2018 50 minutes ago, Beemon said: If one idle circuit does not respond the same as the other, then your idle circuit on that side of the engine is plugged. Or a vacuum leak on that side, which of course will make the idle high too. 1 Link to comment Share on other sites More sharing options...
carbking Posted November 1, 2018 Share Posted November 1, 2018 From your posts, three things come to mind: (1) As mentioned several times by others in the thread, a vacuum leak will render the idle mixture control screws unresponsive. (2) Low compression could also be the cause of an some of your issues; have you run a compression test? (3) We have had literally hundreds of customers with "carburetor idle issues" that were solved by an upgrade to points and condenser! If you are in love with electronics, so be it, but try the points and condenser as a validity test. Not sure when Buick changed from generator to alternator, but electronics require a stable voltage. A generator does not provide a sufficiently stable voltage at idle. If compression is reasonable, you turn up no vacuum leaks, and a test using points and condenser does not find the problem, the carb would be the next place to look. Another thought: the picture is of a beautiful car. Does the engine compartment look the same way? If so, try taking a battery jumper cable from the ground post of the battery to a head bolt. Cannot over-emphasize the importance of voltage at idle with electronics. Jon. 1 Link to comment Share on other sites More sharing options...
56 Buick Posted November 1, 2018 Author Share Posted November 1, 2018 Hi all I could get the idle down to 650rpm only (in park) by turning in the idle mixture screws but that would eventually start to cause rough or erratic idle. The fast idle cam is off, the dash pot is not causing interference and the idle speed screw is completely out. As soon as i set the idle mixture screws so the engine runs smooth then the rpm goes up. I can try putting it in drive as that will reduce the idle. I havent yet been able to find a vacuum leak yet but i can look again. I did only 'just' put the electronic ignition on the car in the hope that may assist the issue. In other words, the issue was there with the points and condenser previously. Of course you can never rule out anything. It is still running the generator. Engine bay is all good and clean. I can try a jumper lead connection. The idle mixture screw on the passenger side engine bank is troubling. The previous owner replaced the gas tank (likely due to rust and whatever else getting in the lines) and apparently had the lines cleaned and carb looked at then. But i dont know exactly how well they cleaned the carb and perhaps thats an issue. I have not yet done a compression test. More work to do. These are the joys of older cars but i do love this car. Thanks Drew 1 Link to comment Share on other sites More sharing options...
Beemon Posted November 2, 2018 Share Posted November 2, 2018 The idle speed screw is completely out? As in not touching the throttle arm? Link to comment Share on other sites More sharing options...
Frank DuVal Posted November 2, 2018 Share Posted November 2, 2018 Most of GM went to Delcotron alternators for the 63 model year. Corvair kept the generator through the 64 model year. I'm sure there are other examples of earlier or later GM adoption than 1963. Link to comment Share on other sites More sharing options...
56 Buick Posted November 2, 2018 Author Share Posted November 2, 2018 1 hour ago, Beemon said: The idle speed screw is completely out? As in not touching the throttle arm? Yes, definitely all the way and not touching. Link to comment Share on other sites More sharing options...
hchris Posted November 2, 2018 Share Posted November 2, 2018 OK , well how about knocking the timing back a few degrees to set say 16" vacuum as suggested by Beemon, then see how it runs. Another factor could be the carb float setting too high, this will make it run a little richer and at idle you may not get enough adjustment out of the mixture screws. But its important that you try these things one at a time to see what effect they have. Link to comment Share on other sites More sharing options...
old-tank Posted November 2, 2018 Share Posted November 2, 2018 Did you ever disconnect the linkage to see if that is holding the carb open? If you can live with the faster idle, you can still set the timing: easiest is to get a dial back timing light and understand how to use it. The governor or mechanical advance will be all in at 1750 rpm and will give 12 degrees advance; the vacuum advance will also be all in and give 9-10.5 degrees advance; initial timing is 5 degrees, so about 27 degrees total advance is your goal Cheapest: rotate the engine so that the rotor is pointing to #1 plug wire and then rotate the engine till it is lined up with 5 degrees on the the timing tab. Attach an ohm meter to the distributor, rotate clockwise until you get a reading, the rotate counter clockwise until no reading (you can do this with a continuity tester too)...the spark occurs just as the points open (no reading).....don't know if this will work with Pertronix. After this advance the timing a few degrees at a time until pinging is heard on the fuel you want to use then back off. My 322's (1955) like 30-32 degrees. 2 Link to comment Share on other sites More sharing options...
56 Buick Posted November 3, 2018 Author Share Posted November 3, 2018 Thanks old-tank, I just started looking at the throttle linkage when i began looking at the return spring setup. I checked with the shop manual and one of the prior owners has set up a system very different to the original. Anyway i played with that and it seems the setup didnt have sufficient pull / leverage to cause the throttle lever to return sufficiently to drop the idle rpm. After rejigging an alternate system i have been able to get the rpm down to 300 albeit the engine is rolling a bit at that speed. Beemon and others were right about the advance as it was too advanced by quite a bit. Using the timing light i have reset the advance at about 7 1/2 degrees. Still got the issue to fix re the responsiveness of the idle mixture screw on that one side. Also, not sure if i have done something or not but the ammeter guage is now just sitting still on the median position and not showing any charge or discharge. Not really sure what has happened there. Thanks to all for the help. Link to comment Share on other sites More sharing options...
56 Buick Posted November 3, 2018 Author Share Posted November 3, 2018 Actually on startup the ammeter just moved very briefly into the red discharge zone and then returned to median position but then does not move from that position despite the revs of the engine increasing. Link to comment Share on other sites More sharing options...
old-tank Posted November 3, 2018 Share Posted November 3, 2018 What does it do with the head lights on? Link to comment Share on other sites More sharing options...
56 Buick Posted November 3, 2018 Author Share Posted November 3, 2018 With headlights on the ammeter goes into red discharge. Then when lights off it goes back to median. Link to comment Share on other sites More sharing options...
56 Buick Posted November 3, 2018 Author Share Posted November 3, 2018 Apart from playing with the timing and using the timing light, the only other thing i have done since i last saw the ammeter working okay was that i fitted another starter relay. I wonder if something has happened with the voltage regulator somehow. Link to comment Share on other sites More sharing options...
56 Buick Posted November 3, 2018 Author Share Posted November 3, 2018 I just remembered that when i was fitting the starter relay, the green wire coming from the current regulator (the middle terminal of the voltage regulator unit) to the starter relay, touched a ground cable and sparked albeit briefly. Perhaps that is the cause somehow. Link to comment Share on other sites More sharing options...
JohnD1956 Posted November 3, 2018 Share Posted November 3, 2018 The Amp meter sitting in the middle is what you want. Its not supposed to swing with engine speed. It shows how much draw is on the system and once your battery is charged it should be back in the middle position. You will see discharge readings for increased electrical loads, headlights, radio, signal lights. But with your engine @ 600+ rpm the generator was turning fast enough to accomodate the power draw. If you are needing more convincing, observe the meter when the engine is off and the headlights are on. It should show a steady discharge. Leave them on for a minute or two. Then shut them off and start the engine. You should see a positive reading till the battery is fully recharged Link to comment Share on other sites More sharing options...
56 Buick Posted November 3, 2018 Author Share Posted November 3, 2018 Thanks John. 1 Link to comment Share on other sites More sharing options...
56 Buick Posted November 8, 2018 Author Share Posted November 8, 2018 I am going to have to deal with that one side idle mixture screw that is not responding. What is the easiest way to deal with that? Do i need to buy a repair kit, remove the carb and overhaul. Thanks Link to comment Share on other sites More sharing options...
carbking Posted November 8, 2018 Share Posted November 8, 2018 8 hours ago, 56 Buick said: I am going to have to deal with that one side idle mixture screw that is not responding. What is the easiest way to deal with that? Do i need to buy a repair kit, remove the carb and overhaul. Thanks Not until you do the compression test, and find that all cylinders serviced by the side of the carburetor with the unresponsive screw have decent compression. This comment from the guy that makes and sells carburetor repair kits! Jon. Link to comment Share on other sites More sharing options...
56 Buick Posted November 11, 2018 Author Share Posted November 11, 2018 Have done compression test. On the bank with the unresponsive idle mixture screw, the figures were from front to back - 110, 125, 130, 112. Link to comment Share on other sites More sharing options...
Beemon Posted November 11, 2018 Share Posted November 11, 2018 (edited) What did the other side look like? Drive it how it is and enjoy it. Make sure you start saving now so when it's on its last leg, you can afford the engine rebuild. It could be the carburetor acting up, it could not be, too. But the carburetor wouldn't cause low compression. I have been battling with engine problems since the rubber on my car first started rolling. Seriously, make a tip jar and fill it regularly. Edited November 11, 2018 by Beemon (see edit history) 1 1 Link to comment Share on other sites More sharing options...
56 Buick Posted November 12, 2018 Author Share Posted November 12, 2018 I was looking at some compression tests on youtube and it appears i should have opened the throttle. Not sure if that affects the reading dramatically. The other bank compression readings were much the same. After the test there was a shockingly loud tick that sounded like a sticking lifter or something... The sound eventually went away after revving for about a minute or so. Anyone ever use that Rislone oil treatment that is supposed to free sticking parts and rings / improve seal and compression? Anyway, there is still no obvious reason why the idle mixture screw was unresponsive on that side. Also, i still have a general rough idle. The idle improves somewhat at a higher idle rpm. But I assume now the cause is the carb. And either try a rebuild kit or instead use a different carb. Link to comment Share on other sites More sharing options...
JohnD1956 Posted November 12, 2018 Share Posted November 12, 2018 The 56 will have a slightly rough idle from the factory. That's assuming you are running a 550 RPM idle. Also if you used the gas pedal starter switch to spin the starter during your compression test, you did open the throttle. The Nailhead is infamous for it's cylinder head design. One of the limitations of it's design is the smallish intake and exhaust valves. In order to improve performance in the early Nailhead years, the 56 camshaft (and maybe others) became increasingly radical to provide for longer intake and exhaust cycles. At 550 RPM that may result in a somewhat lumpy idle. What is the history on your car? By that I mean, did the seller tell you how much it had been driven before you bought it? And how much have you driven it since purchase? What, if any, prior engine work was performed before you bought it? Can you summarize what you've done to it since you bought it? Have you put on new spark plug wires? And if so, did you take care to run the wires the way the factory recommends, to avoid cross fire? Are you still using the spark plug covers? Does your heat riser valve still rotate? And do you know if the valve is still in the pass side exhaust manifold? It is not my intention to overwhelm you with questions. But some additional information may help to determine if the things you are addressing are normal and expected or abnormal for the '56. 1 Link to comment Share on other sites More sharing options...
Beemon Posted November 12, 2018 Share Posted November 12, 2018 If you think it's the carb still, you can attempt to purge the idle circuit before tear down. I have used compressed air in the idle adjustment screw hole. Bear in mind this is not the correct way to do things and the dirt or whatever will still be in the carb, but it could work. Link to comment Share on other sites More sharing options...
avgwarhawk Posted November 12, 2018 Share Posted November 12, 2018 Could possibly be a distorted seat and needle on that adjustment port. Link to comment Share on other sites More sharing options...
56 Buick Posted November 27, 2018 Author Share Posted November 27, 2018 Hi JohnD, unfortunately i know little of specific history. It was apparently restored to some degree around 2011. That owner indicated the dynaflow and the engine were reconditioned but that could realistically mean anything. I did put new spark plug wires in the car and they have been routed to avoid crossfire. The valve in the passenger side exhaust appears to still be there. I am yet to confirm its existence and whether it is operating correctly but on the face of it the same amount of exhaust gasses are being emitted from that exhaust as the drivers side so it may not be an issue. I did try and blow out the passage of that unresponsive idle mixture screw as suggested by Beemon but it had little effect. Unfortunately i haven't had much time lately to do a lot but i did buy more spark plugs. I had previously bought some new plugs supposed to cross reference to the AC Delco 44 but they did not have the extended tip. These more recently bought plugs do have the extended tip (this plug was recommended by Beemon and others) and so far the car is idling much better. Hopefully i will have more time soon to look further at the issue but i am certainly happier. 2 Link to comment Share on other sites More sharing options...
jw1955buick Posted December 29, 2019 Share Posted December 29, 2019 (edited) . Edited December 29, 2019 by jw1955buick (see edit history) Link to comment Share on other sites More sharing options...
56 Buick Posted December 29, 2019 Author Share Posted December 29, 2019 The high idle that couldnt be lowered was rectified by adjustment of the throttle linkage. More 'slack' for want of a better word in the linkage connecting to the carb. That linkage arm has an adjuster screw that I turned to give more length to the point where offset needed to be not at 90° but rather slightly pointing back to the rear of the car. This effectively moved the throttle stop plate back allowing the idle to drop further. The rough idle has been fixed since the carb rebuild. I measured the movement in the throttle valve shafts during the carb rebuild and that was within spec. Link to comment Share on other sites More sharing options...
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