1973 Eldorado Falls on Face When Secondaries Kick In

[50Cad62]

 A big bog from about 60% to WOT. I guess when the secondaries kick in. I checked and rechecked for vacuum leaks, got the vacuum brake and EGR hooked to proper ports. The top butterflies are unlocked when the choke comes off. The bottom secondary plates seem to open straight up, is this too much, will it affect it? Also, I just realized, the transmission kick down switch is MISSING. Is this the problem? I have been working on this a while, I'm about to send the carb out for rebuild, any thoughts?

[76eldo]

The missing switch is part of the problem. It’s very difficult to make suggestions on drivability issues online. You have to drive it.

[The Tassie Devil(le)]

The top plate is there to stop the engine from "dying" when the secondaries are flashed open.   They work on the vacuum pull by what the engine wants as the throttle is depressed, and even though the Secondaries are fully open, the top plate is opened by the air being pulled through.

What happens after the initial "Fall on its' face" event?   Does the engine recover, and scream into life, till you ease off the throttle.

All the Kick-down switch will do is allow the transmission to downshift to a better gear for acceleration.   Without it, the car will just try to accelerate in the gear it is in, lugging away.

Have you tried manually downshifting when mashing the pedal?

Bruce.

[50Cad62]

The car just stays in bog down mode. If I keep it floored, it doesn't accelerate. Good point about putting it in a lower gear. I was going to try and accelerate in first, except the transmission linkage is so sloppy and misaligned, it can't be put in first gear. I need a wave washer, and, a grommet for the linkage, then adjust it.

["Cadillac Kid" Greg Surfas 15364]

Sounds like your secondary air valve is miss-adjusted or the spring is broken.  When you go to WOT with the accelerator pedal, the secondary butterflies in the carb open but the secondary air valve ( the thing that looks like a choke over the secondaries) are supposed to gradually open as the flow through the carb actually increases.
Check your shop manual or any Quadrajet manual for instruction on how to adjust the secondary air valve.
IF the spring is broken or the secondary cam is broken they are available.
Greg Surfas

[50Cad62]

My vacuum break unit has a vacuum hose directly to the port on the carb. In the shop manual, the vacuum break unit has a hose that splits off and connects to the AIR pump. Mine is hooked up improperly because it is not linked with the AIR pump. Do you think this matters?

[The Tassie Devil(le)]

My vacuum break unit has a vacuum hose directly to the port on the carb. In the shop manual, the vacuum break unit has a hose that splits off and connects to the AIR pump. Mine is hooked up improperly because it is not linked with the AIR pump. Do you think this matters?   

I always bypass the Anti-pollution stuff, and run the Vacuum from the Distributor to direct full Manifold Vacuum.

Whether it is a Carby Port, or the Manifold, whichever gives full Vacuum, and not Ported Vacuum.

Bruce.

[Roger Zimmermann]

I always bypass the Anti-pollution stuff...

Bruce, is that not illegal in your country? By the way, I'm trying to do the same!

[James Landi]

Jeez-- why would you venture to open the secondaries-- asking for trouble with 5,000 moving parts that are over 40 years old.  Maybe your car is trying to tell you something important, such as "No, no, please don't push me to the limit!"  I mean this respectfully, so please don't take my suggestion as a criticism.  It's meant as a suggestion.     James

[The Tassie Devil(le)]

Bruce, is that not illegal in your country? By the way, I'm trying to do the same! 

Not for a car that is 40 plus years old.   Anti Pollution stuff didn't come in here till long after 1974, and no vehicle inspections down here.   Don't know of anywhere else that does visual inspections on pollution stuff on the mainland.   As long as the car is safe, and unmodified beyond Factory rebuilding limits, or the vehicle has a Modified Compliance Plate, then almost anything goes.   Hot Rods required Engineering Certificates after around 1985 or '86.

Here, one doesn't have to refit Cat Converters after the car has done over 50,000 Kilometres.

I don't think we got Cat Converters in cars until around 1988, and still no AIR pumps.

But, then again, I could be totally wrong.

Bruce.

PS.   All my pollution blows over to New Zealand.

[fishnjim]

barring any other issues/failures, I'd agree, if it runs but falls on it's face when the secondaries open, the fuel mixture is off.   Either too much air(most likely) or gas going in.   So I'd follow that lead down first.   I'd pull the carb and check it. 

It functions OK at low - mid rpm so the ignition, compression, etc is OK.   So it's fuel or timing.

[hornetball]

Remember that the secondaries, in addition to the spring loaded air valve (the spring can be adjusted), also meters fuel through dedicated passages and jets.  With today's gas, and assuming you don't use the secondaries much, these could be plugged up.  So a quality rebuild is probably the solution.

One thing I do with mine is make sure I do a good pull with the secondaries open whenever I drive.  This freshens the fuel through those passages.  Also gives that satisfying, muffled "WOOOOAAAAHHHHH!!!" sound.

[50Cad62]

RESOLVED. Just got the carburetor back from rebuilder!!!! Works great! There was a cam that actuates the secondary metering rods MISSING. It would have never worked off the secondaries. Now, the car screams! What a joy to drive, and, accelerate the Cadillac.

[The Tassie Devil(le)]

Congratulations on getting the problem sorted out.

Sounds like someone had been playing with the carby and didn't bother to check where something went after completing the rebuild.   Nothing worse than having parts left over.

Bruce.

[TJ Hopland]

Interesting. Kinda makes you wonder how that cam went missing.  I know changing the hangar and the rods can be part of the tune but I don't recall hearing about or ever messing with the cam.   I suppose having the cam missing meant the rods were pretty much fully blocking the jets so all you were getting was an incredible vacuum leak any time you got into it.   I bet what little fuel was getting in there was just too lean to burn so engine was just coasting till the secondaries shut and things went back to normal.     

[50Cad62]

That's exactly the way the car ran, as long as the secondaries stayed open, the car sucked air, and, bogged down. As soon as I let up on the gas, the car accelerated slowly, using only the front part of the carburetor. The guy who rebuilt it said that the cam piece is never missing, it is not even available if you wanted to buy it. He robbed one out of an old carb that he had lying around. He also said that they don't even take that piece out when they rebuild them.

[Matti R]

You need to remove the cam when you remove the axle for secondary flaps. Probably it was forgotten when reassembled. It is kind of plastic plate.

[Cadman-iac]

I have seen a couple of carbs that had the cam missing or broken,  but they had been sitting out in the weather for years and the plastic cam had deteriorated and fell out or had broken away when the air valve was moved.
I haven't looked for one in a long time, but I thought that you could still get them from places like Summit or Jegs in a rebuild kit. At least you used to be able to get them that way.
I have a huge collection of quadrajets that I have been saving for years because I could see they were going the way of the dinosaur 🦕, and whenever I go through one I always take it completely apart, that includes the air valve pieces and the cam.

But yes, without the cam in it, whenever you open the secondaries, you just create a massive vacuum leak.
I would guess that maybe the carb on your car was perhaps a replacement that the PO had stuck on it instead of having the original one rebuilt, and maybe he didn't look at it closely before installing it. It might have been one that sat out in the weather like the few I had. Who knows?
At least now you know what the problem was and it's now fixed.
Enjoy the ride!

Rick