'71 Eldorado: Quadrajet rebuild

[wbdeford]

Rebuilding my carburetor:

manual specifies float measurement of 23/64" for Eldo, but 15/64" for non-Eldo.  It appears to be 21/64" to my eyes...is that close enough?  I don't want to start bending the float for such a small difference if it isn't really necessary.  Anyone know why the difference Eldo vs. non?

I have not yet cleaned the metering rod assembly, because I am not certain what material the loose component (see attachment) is made of and whether it can withstand the carb cleaning chemicals.  Can it?

Thanks!

[Julien Abrahams]

No it cannot cope with carb cleaner. It also says this in the shop manual. It is a kind of plastic. I don't know for sure about the float settings.

[wbdeford]

Thanks, Julien....there is no replacement for that plastic piece in the kit....how should I clean the assembly?  brake cleaner?

[TJ Hopland]

The float arms should bend easily.   There is usually a section in the arm made to flex.   The other thing you need to check related to the float is that the arms don't hit that plastic plug thing that fits in the top.    I first measure it without the plug and then again with the plug to make sure it does not change.   If it does it all it usually takes is a little work with a dremel type of tool or file on the plastic to make a little clearance.  Been seeing that issue more and more lately.   

I have never soaked that rod assembly in cleaner overnight or anything like that but I have used spray on them and it didn't seem to hurt that plastic thing.  If the plunger part is that nasty perhaps you could find a small test tube like container that would allow the main part to be sumurged in the cleaner but leave the top out. 

[Julien Abrahams]

I have cleaned mine using WD40 and a toethbrush. Then I used gasoline to clean off the WD 40. Although a bit of work, it worked like a charm. The only problem I had was that the rods would not stay in place when I pused the plastic ring in the recession. The shop manual states that the metering rods should be held in place by the plastic ring (the bore were the ring falls into is just a hair smaller then the ring, so it would fit snug. However, the spring exerts opposite tension, pushing the rods up. In the end I used a very tiny piece of the thinnest gasket paper I could find, to 'lock' the plastic ring in place until I installed the air horn a couple of seconds later.
I think the '71 is slightly different from the '67, but the changes are not huge. On google and youtube you can find several videos of guys disambling and reassembling a quadrajet. This helped me a lot.

[wbdeford]

Thanks, guys!  I doubled and triple-checked the float and the procedure, and it seems I was measuring at the wrong place--not far enough out to the "toe".  It seems correct now.

I used a small pill bottle to submerge the lower portion of the power piston assembly in cleaner.  Great idea!

[wbdeford]

One more question....the manual shows a retaining clip for the power piston, but I did not find one in mine.  It looks like this: http://quadrajetparts.com/rochester-quadrajet-carburetor-parts-quadrajet-power-piston-retaining-clip-for-quadrajet-power-piston-p-212.html

That site says they are used on "some" quadrajets.  Is it possible mine never had one, or should I order one?

["Cadillac Kid" Greg Surfas 15364]

Nice if you have it. Without one installation of the air horn (carb "top")  is a little trickey.
Greg Surfas

[wbdeford]

thanks!  will order one, then.

[TJ Hopland]

Does that go in place of that little plastic bit?

I have been sticking it (or them in the case of the 75) in the gasket first and using the gasket to hold em down while the top goes on.

[wbdeford]

Found out the plastic bit is called the power piston bushing....the clip looks like this...

TJ, You bring up a very interesting point.  Neither the shop manual nor the rebuild kit mention or show the plastic bushing as a separate component.  As can be seen in your pic, the bushing is, of course, a little wider than the rest of the power piston, but the pictures in the manual don't show that (although one of the pics is a little distorted and it's hard to tell)

Quadrajetparts.com has a page about the bushing ( http://quadrajetparts.com/rochester-quadrajet-tech-t-12_29.html ) , and it says "Early Quadrajet carburetors manufactured in the mid 1960's used a metal retaining clip instead and do not use the nylon retaining bushing."  So, either GM failed to update the shop manual with this change-over, or someone made the change in an earlier rebuild.

So, it is now clear that there is no need to have both.  Thanks!

[wbdeford]

This is how loose the power piston bushing (plastic thingy) is in my Quadrajet.  Thinking I should replace it....this is too loose, right?

https://youtu.be/Siu9jWpewTA

[wbdeford]

On the other hand, does the bushing only exist for installation--to hold it down so you can install the air horn without risking the metering rods coming out of the jets?  Once the air horn is on, it would seem impossible for the power piston to come up far enough for that to be a problem. 

[Julien Abrahams]

You are right. Once the air horn is in position, the power piston simply cannot go anywhere. I would not worry to much for the missing bushing. It is basically there to hold the power piston in position, until the air horn is installed.
Be careful not to bend the needles, they are pretty fragile and it is a bit of a pita job to get them to go into the jets and for them to stay there until the air horn is in place.
Could luck.

[wbdeford]

Thanks, Julien. I found it wasn't too difficult to keep the power piston held down just enough while lowering the air horn.  I held the power piston down (gently) with my thumb and the accelerator pump down with another finger while lower the air horn with my other hand.  Once it was most of the way down, I released the pump and switched to my pinky on the power piston to get the clearance down as low as possible before carefully releasing the power piston and gently lowering the air horn the rest of the way.  The first time I felt resistance and immediately pulled the air horn back up.  The needles had popped back out.  But I got it on the 2nd try. 

I found that the key to getting the needles into the jets was just to shine a bright light down in there...made it pretty easy to eyeball where everything was.

Carb is now mostly back together, awaiting a replacement vacuum break (choke pull-off).  I haven't tightened the screws, or squeezed the horseshoe clips, or full inserted the accelerator pump arm pin in case I have to loosen some things to get the vacuum break and its rod on.

[Scot Minesinger]

William,

Seems like you are on the right track, not guessing, not forcing, and taking your time.  It should be a success.  After the carb is installed and you are ready to turn the key after priming carb, be prepared to adjust up the idle for both fast and warmed settings.  For some reason removing a carb where idle was set good, rebuilding, and re-installing the idle screws need to be turned up.  Then re-torque the four mounting bolts and 9 or so air horn screws after the first drive and then again at 100 miles.

If your carb was way off before with vacuum leaks and etc., probably a good idea to re-set the timing too, foot on brake while in drive-per manual.

Keep us posted.

[wbdeford]

New vacuum break (aka choke pull off) arrived, so now the carb is together and am doing adjustments.  Got through the first few and everything is making sense until:

page 6-80 in shop manual: 92. Vacuum Break Adjustment

< set fast idle cam on highest step and apply vacuum....done....>

"With the diaphragm stem seated, lift the vacuum break lever until adjusting tang contacts link between air valve lever and vacuum break stem.  Choke valve should move to a near closed position."

This happened, but then it says:

Dimension between the front wall of air horn and lower edge of choke valve should 0.300. 

0.300" clearance and near closed do not sound consistent to me.  Is this a typo and should read 0.030"?  I was a good bit over 0.030" but nowhere near 0.300". 

[Glen]

That adjustment in the 1970 manual says it should be 0.235.  So I would assume the 0.300 would be correct for your car. 

The 70 manual also uses the “..near closed position” statement. 

[Julien Abrahams]

I also beleive that 0.30 is correct. The idea of the choke pull off is to open the choke valve a bit to allow more air to be drawn in when the engine has been flooded during cranking.

[wbdeford]

Great....will go with the .300 then, and that does indeed make more sense after further consideration, in spite of the confusing "near closed" language...thanks, guys! 

Next possible problem...when I checked the Secondary Throttle Opening, the linkage is exactly as the manual says it should be, but the secondary plates don't open fully (see pic).  Is this normal?  Once in this position, I can move the plates with my hand to roughly the same angle beyond vertical.