gmeyer316

55 century carbissues

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Here is a pic with the engine hot, I straightened the acc pump rod and relocated the return spring, still hard to keep running a a stop light.post-154034-0-32438900-1436664843_thumb.

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Benefits of AACA Membership.

found a little vacuum leak where the line goes through the firewall. Idles good now in neutral, idles rough and slow in gear.

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found a little vacuum leak where the line goes through the firewall. Idles good now in neutral, idles rough and slow in gear.

 

 

Ok, a vacuum leak can ruin a whole day.   Determine one more time there is no other vacuum leaks.  Additional air coming from anywhere other than the throat of the carb will make idle rough and lean running.   Once you are sure there is no other leaks adjust the fuel mixture screws again as well as the idle speed screw.

 

And to be sure, the carb has been off and all the screws keeping the entire carb together have been snugged up?    

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Now that you straightened the pump rod, that repositioned the internal (whatchamacallit) and could very well be what is now making it idle rough when in gear. ;-) That was fine previously correct?

Also, Engine Idle RPM (warm-choke off) is 450rpm

Edited by smspaul (see edit history)

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doesn't idle rough in gear it just dies, do I need to bend it back again like it was?

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doesn't idle rough in gear it just dies, do I need to bend it back again like it was?

That would be my first move. Or just leave it straight, take the cover off and adjust the pump arm to compensate for the position change that occurred when you straightened it.

Edited by smspaul (see edit history)

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Did you check the ignition? Here is a story of one that did not idle but ran well at high speeds: http://forums.aaca.org/topic/210599-is-it-the-carburetor-this-time/?hl="is+it+the+carburetor+this+time"

The hex and slotted screw you referenced is the idle speed adjustment screw and if it moves the throttle shaft as you screw it in and out it is probably working ok.

After you check the ignition, the carb 'may' need a rebuild (the inside may be as crusty as the outside).

The throttle return spring is in the wrong place, but should work for now.

Check the ignition first: dwell, timing, vacuum advance.

Willie

Did you do all of this?

Your rod was bent incorrectly. Why would you bend it back?

Edited by buick5563 (see edit history)

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doesn't idle rough in gear it just dies, do I need to bend it back again like it was?

It wasn't running well like this. Was it?

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Don't run away, dammit!!!

I have two more questions.

Where does that hose go from the left oil filler?

What is that Home Depot plumbing piece on the intake manifold vacuum port?

Neither are stock.

I wouldn't trust the "freshly rebuilt carb", while we're at it. The upper gasket looks to be enhanced with pookie (gasket maker) of some sort. That is some rigged BS if it was really used.

I AM NOT slamming the OP asking questions. I would just like to make sure the answers he is receiving are being tried.

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Good eye Mike and those may be pics of my engine you're referencing instead of the OP.  They were meant to show how the pump arm looked without a bend, the linkage, and the return spring attachment points.  The hose from the oil filler cap and the T off the intake manifold is where I plumbed in a PCV (selected to pull minimal vacuum) on the car because I didn't want to bust into the back of the valley pan where the road draft tube is.  This keeps the blowby oil film from getting all over a clean engine compartment when driving and works pretty good.  It comes off and the regular oil cap goes back on for shows and just disconnect the T.

 

Back to the post, I also think its best to keep the pump arm straight since the lever that the linkage attaches to is swaged onto the pump operating shaft, so if anything this resulting subassembly should be back in its proper position.  My expectation is this adjustment would only have an effect on acceleration and not idle.

 

The hex idle speed screw only going in a half turn before bottoming out doesn't sound right - seems my recollection is 1/4 turn is about 50 rpms but don't quote me on that.  There should be a few turns of adjustment left in it rather than half turn. Think mine is only 1 1/4 turns in from when it contacts the throttle lever.  Maybe when the cold engine is running on the fast idle cam there is enough throttle applied to keep running while stopped in drive.  At hot when it comes off the cold cam and drops against the low speed hex screw it might be too slow.  Slow enough that it can keep going in N but not with the load in D.  If the screw is really "in" that far and is properly mounted in relation to the throttle lever then the carb is likely running off the main circuit with the throttle plates cracked open enough that its bypassing the idle circuit. Or maybe the threads on the hex screw are compromised and need to be cleaned up.  This doesn't yet explain why it worked earlier then "started acting up".

 

One could also back out and remove both mixture screws (after counting how many turns in until they seat) and shoot some compressed air in the circuit at about 10 psi.  That has worked for me when some crud made its way past the glass bowl fiter and screen in the carb messing up my idle circuit.  Got lucky and avoided having to dig into the carb.

 

Numbers would really help narrow down the problem.  Hoping we'll see some warm idle speed, timing, vaccum and/or dwell measurements and how good the fuel and fuel filtering is.  Lots of experience available on the thread to solve this.

Edited by KAD36 (see edit history)

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Oops. My bad! Will use my good eye next time.

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Most "pookies" are not gasoline resistance, much less ethanol resistant.  Hence, it all needs to be cleaned up/out and removed soon.

 

Just soaking the carb and putting a fresh (new, not NOS) carb kit with a QUALITY (correct OEM thickness!!) base gasket only means you've got a "clean carb", but (as mentioned in my earlier post) will NOT address any hidden "deposits" which the carb cleaner will not dissolve or remove.  Whether it was a "Professional" that rebuilt it or anybody else.

 

NTX5467

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Ok. So we have not established anything yet. Let's assume for a minute that the carb is ok (after rebuilding it again without gasket maker and no gas seeping out of the carbs fuel inlet screen - both visible in post 10 ) and the timing is good.

Next thing to do is de-rig the intake manifold T. Even without seeing the rest of the engine, here is my guess. That plumbing pic (post 10 passenger side) is a vacuum hose going directly to the wiper instead of through the fuel pump. The wiper is probably leaking. There is a vacuum leak.

Yes?

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The OP is gone.  He wants it to be a carb issue that is fixed externally.  From his introduction post, this car is new to him, pictures show a newly painted engine with lots of rigging and omissions.  No way to tell what was done inside or outside and apparently he wants no guidance to find out.

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Kind of a shame. Four of the best 1955 gurus plus Jon the carb expert tried to help. Oh well. I'm out now.

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I just got a look at this thread. "If the car was mine" I would start it and bring it up to the temperature where it cuts out and let it die. Then real quickly remove the air horn and float bowl cover.Allow that the fuel will be lower when the floats come out and look in all the chambers of the carb to see where fuel is missing, but should be there. Play attention to the accelerator pump well as well as the other little nooks and crannies. Once you have looked everything over and made your mental notes, put the float cover back on,tart the car and shut it off quick. Uncover the guts again and snoop around. What ain't right? Where are the vapors rising from? Is the pump well empty?

 

This is stuff I have actually done on these untenable problems. What I would be looking for is a fuel chamber adjacent to a vacuum passage that may have developed some porosity over the past 60 years. When you say "Hey! There's supposed to be gas in there." You may be on the track. I had it happen on a 4GC Rochester, but they are all made out of the same cheezy metal. I replaced the bowl and lived happily ever after. I was always going to coat the area I deemed porous with expoxy and test it. More pressing stuff came up.

 

It's worth a try. Always remember "The level of perfection one can achieve is directly proportional the the number of times they are willing to take it apart and do it again."

Bernie

Edited by 60FlatTop (see edit history)

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Well Im back been gone a few days, I wasn't ignoring any of you guys and I appreciate any help any of you can given me. Yes the car is new to me and its been years since I messed with these old engines. I got it from a guy who is familiar with these old Buicks with lots of rebuild experience, and I am indeed interested in your ideas and advice in order to solve this dilemma. I don't care what kind of issue it is and would like to solve it whether it be internal or external. Im just an old biker who cant ride any more because of arthritis in my hands so I thought I would try classic cars and I really like these old Buicks. I used to work on the old forties and fifties Chevys when I was young, I just need to refamiliarize myself with this fabulous old iron.

Now, I checked out the points and they were pitted beyond recognition so I replaced them and the condenser, the dwell is now 29, the book says 28-32 and the timing is right on. I have eliminated the vacuum line to the wipers so no leaks there now the only vacuum line is the one from the pump to the manifold. .

It started cold better than it has been and ran smooth till warmed up, once warm, idle fluctuates a bit and when put in gear dies almost immediately. I have no doubt that it is a carb problem at this point was just hoping it might be something easier.

I realize there is a wealth of experience knowledge and wisdom here, that's why I came here in the first place.

I thank all of you for any help you have sent my way and hope to continue a friendly dialogue with all of you.

Thanks Bernie

Greg

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Oh and the hose on the breather used to be hooked up to the vacuum line it now has a bolt in it to keep it plugged till I can get a new breather cap without the hole for the pcv valve.

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Assuming that it was running/driving when you got it. I think what might help everyone here is if you could list out what changes and adjustments you made since you've had it. Preferably in order of how you made the changes and adjustments.

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That might help Paul, lets see what happens.

 

Still looking for 1) vac gauge reading at idle if possible to verify Mikes hunch, 2) rpms at hot idle in N and D and 3) rpms when timing was taken. 

 

Getting to idle under 400 rpms hot to let off the vac advance and allow an accurate timing measurment would seem pretty tough given the symptoms unless the advance was unplugged during the measurement.

 

A vac leak to kill the engine in D would have to be pretty big (and audible). And it would really be stumbling in N - hard to not notice.

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Just thought of something, you said the timing is 'Right on'. ....how does it run if the timing is advanced another 5 degrees or so?

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Hopefully, too, the timing was set/adjusted AFTER the points were installed and adjusted as point dwell change has a direct affect upon ignition base timing.   Points, then base timing, then hot idle speed, then idle mixture adjustments/tweaking, recheck idle speed and adjust idle speed and mixture until all is "in spec" and the engine operates "nicely".

 

If everything else has been done "to satisfaction", then it just might need a little more (hot) base idle speed to keep running reliably?  In some cases, especially with older vehicles and older (used) engines, the "factory specs" can be a good starting point for things, but if a little more idle speed might make things work better, then that's what the car is telling you it desires (like an additional 50rpm or so).  Once the idle is solid and reliable (in gear and in Neutral/Park), THEN you can worry about the apparent issues with the accelerator pump and related items.

 

It looks like things are progressing in the right direction (chasing vac leaks and such).  Please keep us advised of your progress.

 

NTX5467

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Looks to me that you need to start over with the idle mixture screws. See what the book says as a starting point to back them off. Bottom both screws and make a note how far each one was out from lightly bottomed. Back them both out equally to book specs, maybe 1 1/2 or 2 turns each and adjust from there for max vacuum or rpm. Adjust idle speed screw for 450-500 in park, some readjust of mixture screws may be required if idle was too high.

Sorry if I missed that you already adjusted idle mixture by the book, That is always the recommended procedure.

The reason you need the idle lower than 450 to set timing is to be certain the mechanical advance is out of the picture and not affecting timing.

OOPS! NTX5467 AND I WERE BOTH TYPING AT THE SAME TIME.

Edited by TexasJohn55 (see edit history)

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