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Post Info TOPIC: Need Help or Advice on 66 Holley Carb Issues
jim larson


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Need Help or Advice on 66 Holley Carb Issues
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With to much time on my hands I decided to rebuild my carb and install the correct list # main body on my 66.  I ordered some new tires today, so I thought I should start the car and get it running.

The good, no fuel leaks and it started on one pump of the foot and a turn of the key.

Heres the problem,  I couldn't get it idle down.

All I did was replaced the main body with the correct numbered main body and did the standard rebuild, gaskets,needles,  fuel filter, accelerator pump,  along with putting in a new secondary diaphragm. I reused all the other parts from the carb I was using last summer.  I also resurfaced the 3 surfaces on the main body along with resurfacing the throttle plate.  I did this 3/8" piece of plate glass and 320 sandpaper to get any warpage out.  There was very little warpage. 

Last summer distributor was  set at 14 degrees advance with the vac can plugged and idle at 600 rpm.  When I plug in the vac can it would idle at about 800rpm. And the car cooled good at 95 degree outdoor heat.

Now with the vac can plugged and set at 14 degrees advance it idles at 1050 with the idle screw back completely  off the throttle shaft. I had the advance set at 14 and the car ran fine last summer and also ran nice and cool with the original recored radiator. Air mixture screws are only backed off 1/2 a turn. If I lowered the advance the car to, so say 10  would the car  would run hotter.  I was told by  TC members to set my advance at 14-16 with the cam that I had.  If I lower the advance I think the car will run hotter; but not sure.  The car wants to diesel now when I turn off the key which it did not do last summer.  So I am thinking to much advance. 

Is this a distributor problem?  Or a carb problem?  Or a timing problem?  Any Suggestions?  Thanks in advance.

 

 

 

 



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Jim L

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Lost in the 60s


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Have you checked the fast idle cam and screw ? The cam could sticking. Is the choke opening to let the fast idle cam drop ?

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Mitch D.   River Falls, WI

Lifetime member of the "Cars apart Club"

1966 Chevelle SS 396 M20

1970 Chevelle SS 396 M20

1967 Camaro SS/RS 350 M20
jim larson


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Lost in the 60s wrote:

Have you checked the fast idle cam and screw ? The cam could sticking. Is the choke opening to let the fast idle cam drop ?

 This is the old divorced choke style, with choke fully off and engine warn, the tang on the end of the primary throttle shaft is not making contact with fast idle cam.  Throttle plates are fully closed and idle screw is just barely touching the arm on the primary shaft.

I am a novice here and don't understand what all makes these carbs work. I am thinking that somehow two much gas is getting in though the idle circuit.  Could there be something about the main body that I replaced that would cause this?   Or something about the throttle plates allowing to much gas in. I also replaced the spark plugs and one didn't look like it was working too good.

 



-- Edited by jim larson on Thursday 19th of March 2015 05:49:49 PM

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Jim L

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67ss


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It looks like you may have installed a new diaphram for the vacuum secondaries. Check to see if the secondaries are hung open a little bit. I think there are two different lengths on those.



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Chris P
East Central, Mn

66 Chevelle 300 deluxe
jim larson


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67ss wrote:

It looks like you may have installed a new diaphram for the vacuum secondaries. Check to see if the secondaries are hung open a little bit. I think there are two different lengths on those.

 Yes I did install a new diaphragm,  The guy I bought it from said it was the correct one; but who knows  I thought I checked the length with the old one; but I will check to make sure the secondary throttle blades are closed and not leaving too much of the idle circuit open.  I did not mess with that little screws on the bottom to close or open the idle circuit on the secondary side; but I did take the throttle plates out and re- installed them with proper screws.  I also removed and re-installed the primary throttle blades and I think they close as much of the circuit as before.  I think there is suppose to be a specific measurement as far as how much of the slot should be showing.

I only have the air mixture screws about 1/2 turn and I have read that they should be out 1 to 1 1/2 turn;  The 1/2 turn is suppose to be and indication that the blades are not closing enough; but there is no adjustment to move the blades so they close more.confused  And it seemed to run fine last summer with the same throttle plate, except for the little resurfacing I did along with removing and re-installing the throttle blades.

Well I will have to start the car tomorrow and check everything over again.



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Jim L

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Is it possible to install the throttle plates incorrectly on this carburetor. I just worked on a carburetor and it was possible to install them backwards, in other words the holes drilled for the screws where not in the center of the disk.
If installed backwards the throttle plate would not close enough to allow the idle circuit to function because the idle RPM was to high.

I'm sure you have it installed correctly, not even sure you can install yours backwards but, it might be worth checking.

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Kevin

Northwestern Ohio
jim larson


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dashboard wrote:

Is it possible to install the throttle plates incorrectly on this carburetor. I just worked on a carburetor and it was possible to install them backwards, in other words the holes drilled for the screws where not in the center of the disk.
If installed backwards the throttle plate would not close enough to allow the idle circuit to function because the idle RPM was to high.

I'm sure you have it installed correctly, not even sure you can install yours backwards but, it might be worth checking.

 I will check that Kevin.  I thought it was impossible to do that but I have been wrong in the past.  I was thinking the same thing last last night.   I took the trottle plates off and shafts out to resurface the sides to make sure there was no warpage and vacuum leak.  I have a spare throttle plate, shafts, and blades to experiment with this morning.

Also in light of what Chris said: I think I can disconnect the arm from the diaphragm and use something to tie the secondary shaft/blades shut to see if that is an issue.  I also have another secondary I could throw on the carb.

I was hoping Bob from White Bear would comment, since he is kind of a Holley expert.



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Jim L

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Well I took the carb off and think I know what the problem is.  The primary throttle shaft and throttle blades don't close enough.  Look at the photo, you can see where it road last year and it is much more open, exposing to much of the idle circuit. Backing off the idle screw does not allow it to close far enough.  I think I had to heat this shaft a little with a torch to get out a broken throttle blade screw that broke when I removed the throttle blades to do the resurfacing.  So I either screwed up the shaft or installed the blades incorrectly.

I believe the blades are installed correctly, since they are installed with the # 109 to the bottom and to the center as they are in 2 other old throttle plates I have.  The secondary diaphragm is of the length that allows the secondary throttle blades in the same position as before.



-- Edited by jim larson on Friday 20th of March 2015 10:35:47 AM



-- Edited by jim larson on Friday 20th of March 2015 10:37:09 AM



-- Edited by jim larson on Friday 20th of March 2015 10:38:41 AM

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Jim L

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Lost in the 60s


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I would remove all the external linkage and turn the shaft by hand to see if it is binding. If it closes without the linkage, you will know it is one of them that needs adjustment.

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Mitch D.   River Falls, WI

Lifetime member of the "Cars apart Club"

1966 Chevelle SS 396 M20

1970 Chevelle SS 396 M20

1967 Camaro SS/RS 350 M20
jim larson


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I didn't install the throttle blades properly.  They would not close enough to close the idle circuit. Blades have been taken out and reinstalled, carb is back on, car running fine, idle set at 600 rpm, with 12 * of advance.  I will check the dwell as soon as we get over this approaching cold/snow storm, thanks everyone.

 

 



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Jim L

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Glad you got the issue resolved. Stinks you had to go thru all that to get there.

I'm curious why you didn't take the timing up to 14° again, since it seemed to help with the temperature.

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Mitch D.   River Falls, WI

Lifetime member of the "Cars apart Club"

1966 Chevelle SS 396 M20

1970 Chevelle SS 396 M20

1967 Camaro SS/RS 350 M20
jim larson


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Lost in the 60s wrote:



I'm curious why you didn't take the timing up to 14° again, since it seemed to help with the temperature.

 I ran out of time.  I kept get it at 12 to 16 and back and forth.  I plan to do that again when the weather gets nicer and also check the dwell.  Do you know of a good way to control the movement of the distributor when trying to set the timing.? I need to get an assistant over for a second pair of eyes.



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Jim L

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