I am having a problem with the q-jet not idling down, even when warm... I have even diconnected the throttle linkage to the gas pedal so the carb is not binding there. It will idle around 1000-1200 rpm and even with the idle speed screw turned all the way out it will not idle down. In back of the idle screw along the side of the carb is a coiled spring with linkage attached to it (TRYING TO REMEMBER) if I push on that linkage some it will move enough that it will idle down then. What is that spring? Sorry I don't have any picas so I'm not sure I am describing it correctly. One thing I did do was dial back the electric choke a little to crack open the throttle on cold start but I don't think that would cause it to not idle down would it?. Any ideas on what stopping it from idling down. Thanks, Barry
Re: idle spped that coiled spring is the secondary throttle valve return spring. sounds like your secondarys are sticking open slightly,causing the rise in idle speed.
Re: idle spped There's got to be a bind somewhere in the linkage between the primary and secondary throttle shafts, or something holding the secondary throttle blades open. First thing I would do is look down the secondaries with a flashlight (car not running) and visually confirm whether the secondary throtle blades are all the way closed. Could be hung up on the gasket or something like that. If they are closed all the way, it's got to be something in the linkage on the lower driver's side of the carb that actuates the secondaries.
Re: idle spped Will give that a look.. I didn't have that problem last fall, but over the winter I've replace the stock manifold with a S divider and a 1" carb spacer so there may in fact be something blocking the secondaries some where. Thanks, Barry
Re: idle spped Something zi have seen in the past as well, is the secondary throttle blades being slightly misaligned, causing them to hang open. This could have occurred while the carb was off the manifold, or while reinstalling it. Ray
Thanks Ray, had a hose blow out today so won't get a chance to 'tinker' with it until possibly this weekend. I also ordered a book by Cliff Ruggles that i hope will give me a better idea of the working of the Q-Jet. Barry
Re: idle spped Is It Possible The Choke Is Not Getting Hot Enough To Disengage The Fast Idle? Or It Could Be Binding On The Electric Choke Side Of The Linkage. Good Luck
Re: idle spped I did turn the electric choke a bit clockwise I think, so is it possible that that's the reason it won't idle down? I will try turning after it warms up and see if that helops, as right now the idle speed screw is turned out so far there is a 3/8" gap between it and the plate it touches. Barry
Haven't been able to work on carb yet but did get the tak reinstalled and filled 1/2 way with gas. Couple of obseravtion---- tried turning electric choke to see if it would help idle nope. Tried turning fast idle screw in to slow down idle worked a littlew but not much. However once cooled down I re started engine and in reved very high , like 4,000 rpms until I hit the gas pedal twice then it slowed down... acted like throttle was stuck..... once idled down to 1000rpm I was able to check vacuum and it was 17.5" with an occasional drop to 17" for a second though I couldn't tell any difference in RPMs. One thing i did notice if i pushed on the secondary plates it did drop rpms down to the p[oint of almost stalling... why? Anyway will most likely pull carb tomorrow, but I need to get the bed bolted down first. Barry
On most carbs, turning the fast idle screw IN RAISES the fast idle speed. Probably why you got the 4000rpm surge on startup. When you say you pushed down on the secondary plates, what are you referring to? If you mean the upper butterflies, pushing those open raises the secondary metering rods, and you will flood it if the secondaries are open, even just a little. Figure out why the secondary throttle plates are hanging up and you will solve your problem
You are correct!! I took the carb off and brought it in to check it out some... With the fast idle turned all the way in the primary butterflies are cracked open about a 1/16". As I turn it out, it cause the butterflies to close and also allows the primarie's idle screw to come back into contact with the primary throttle plate.... This may have been a lot of why I couldn't get it to idle down( because the fast idle speed was turned to high!?!) I will spray the whole carb down with cleaner and reinstall, as soon as I can find a gasket...which makes me ask.... I have a spread bore 1" plate under the carb, so I should install a spread bore gasket both to the carb side and the intake side correct? Reason I ask is I can't find anyone that has them and am wondering if I should just buy a couple carb gaskets and cut the "guts" out of them? Another quickie, before I took the carb of I did a vacuum test and at was able to get 17 1/2" of vac. off the carb port that goes to the transmission. It did fluctuate a little down to 17" ---- all this at 8 degrees of initial timing with the vac advance off and plugged as was the port for the vac on the carb. Is that a little high? I may have the initail timing a littl low as i took it down to there to see if the idle speed would decrease (will try advancing it now being that i"MAY" be able to get a better handle on the idle speed with the fore written info.... Any help?? Thanks, Barry
Need to find two spreadbore gaskets. Can't change a square bore into a spreadbore--too narrow You mean the vacuum? Vacuum can never be "too high." 8 degrees of initial timing is a good starting point. Read the "Power timing your Buick V8" thread in the Buick FAQ section here
Since you mentioned that closing the secondary throttles slowed the idle, I would make sure that they are completely closed. I would also turn the slow idle in until the screw just contacts the throttle linkage. Also, make sure that opening the choke all the way allows the fast idle cam to drop all the way. It is gravity driven, and uses its weight only to drop. Anything making it stick, including the choke's not opening will cause a high idle. Push the linkage open rather than the blade. When checking the secondary throttles, it may be necessary to slightly loosen the screws, and realign the blades until they fit properly in the body. That will cause the linkage to completely unload. Also, make sure that the shaft is not bent, or binding in the body. Overtightening the carb on the manifold, or warpage can cause this. Very frequently, if the carb is placed on its base with the throttle slightly open, it will misalign the blades. I have also seen bent linkages between the primaries and the secondary drive cause binding against the float bowl. PM me w/ questions, if you like. Ray
OK a little update... took off the carb cleaned it ( carb cleaner) and checked to see if there was any binding.... no. Bolted it up to the 1" riser plate and the primaries were rubbing!!! Seems the riser has a bit of taper to it as I turned it over and rebolted and had plenty oc clearance for both Primaries and secondaries. Put the carb back on with the riser in the correct position... and BAMMM idled like it aought to ... specs. are:12 degrees initial-- 13-1/2 -14" at 800 rpms. Everything seems back to normal.. I did just get an Accel Adjustable vac. advance kit which does have a bushing in it, that says to replace the old one.... I haven't taken the distrib. apart yet but what "old one" are they talking about? Also got a Mr. Gasket Advance curve kit with three springs black (lightest spring ) silver( med) and gold (heavy).along with the plate /weights/and bushings those look pretty straight forward so soon , I will be trying to put some fire in that dragon!! When the wife gets home probably Sat. I will see what the mech. advance is and what the total is. Is it neccassary to know what the stock timing total is or should i just jump in make the mods. then test it? Is there a way one person can rev engine to a certain RPM and timing at the same time? Thanks to all that have helped me so far you guys are great!! Barry Barry
Opps meant to ask once the carb has been cleaned what should be put on springs- acceleator pump rod- etc, for good lubrication to stop friction bind. WD-40? Barry
To answer your question, nothing should be put on the linkage, except to clean it. GM recommends leaving the linkage dry after cleaning it, as lubricants thend to attract dirt, dust or eventually harden due to heat cycling, causing binding. The bushing refgerenced in the vacuum advance kit is used, SOMETIMES to limit vacuum advance. The spring controls the rate of advance, and the bushing controls the limit of the advance. It is typically used when certain number advances are used in lieu of others, limiting the necessary size of stock. Carefully check the numbers on the advance kit, and try to duplicate the numbers. The purpose of the vacuum advance is to allow good driveability with limited throttle openings. Increase advance until PART THROTTLE ping becomes an issue. Remember when the vacuum advance operates. It operates during high manifold vacuum. WOT performance will not be affected. It will therefore affect light throttle driving. It will also affect transitional driving, when progressively opening the throttle to about 3/4. The screw affects the counterforce applied to the vacuum supplied to the diaphragm. Backing the screw all the way off will provide maximum advance. Make your adjustments in 1/4 turn increments, just until part throttle ping disappears. Let us know how that goes. Something to consider is that the spacer will affect the part throttle cylinder filling, directly affecting the advance necessary to cause the ping. Also, make sure that any controls, including the TCS are bypassed, as these control the applied vacuum. Questions? PM me if you like. Ray
Thanks for the info Ray... I had a little bit of time today so I installed new springs and weights. Inital timing is 12 degrees with the mechanical all in at 25 degrees @1700 rpm- total is 38 degrees. I still need to do some tuning on the fast idle as it seems to be running a little rich(?). I have a hard time keeping it running on cold start but once warmed up it's fine... Barry
Might want to crank that down some, or make some more changes. 38 total is pretty high. Usually 32-34 is the maximum. I assume you are familiar with the "Power Timing Your Buick V8" thread in the Buick FAQ section?
