Hello,
I have checked and replaced my in line fuel filter, checked and found the inlet paper filter is fine, my choke linkage is disabled and wired so it will not interfere with the secondary throttle blade opening, my choke pulloff at least in the driveway is fully open and not interfering with the air valve door, I have adjusted the air valve door to zero tension plus 1/8 turn. My hanger (k) and rods (ch) are not bent or binding in any way. It used to pull great on the secondaries.
Now if I step on it, it looses power, and sounds like its running on two cylinders. It does not smoke black at all. I can be running along at 2500 RPM on the primaries, stab it and it will go flat on it's face, slow right down. I go 50mph flat out in overdrive. If I lift out of the secondaries it comes back to life
I believe that unless the air valve is mysteriously staying shut that I must have dirt or something blocking the secondary curcuit. But what??

Any ideas would be greatly appreciated!

Eric

 

It's probably exactly the opposite - there isn't enough tension on the AV spring, and your secondaries are just flopping open.

Try more tension.

Another possibility is in "disabling" the choke linkage, you actually tied the AV shut as well. The choke pull-off is intended to hold the AV shut momentarily when you nail it (just the initial shock), then the tension takes over from there. If you rely only on mechanical or only on vacuum, you won't be able to eliminate bog. I discovered this little fact the hard way myself (sure wish I could find that pull-off rod...).

 

It did the same thing when I had more tension on the A/V.

It runs no different with the choke linkage wired shut than it did before.

Even if the A/V was flapping open, wouldn't it would bog and then eventually catch up and run? This is not a bog, this is flat out death. THe thing that gets me is this used to run fine, It's as if the secondary jets were plugged shut.

What feeds fuel to the secondary circuit? I know the primaries discharge into the boost venturis, but I see no such thing looking down the carb throat on this.

I am going to hunt down and buy that book on Rochester Carburettors this weekend

Any thoughts on what else to look for? I'm going to check fuel pressure, try to rig a guage I can see while driving it.

Eric

 

Yes, if the A/V just flops open, normally you'll get a HUGE bog and then it will pick up and boogie.

As a test, you can take a screwdriver and simply unbolt the A/V doors from the A/V rod. It will bog like a bitch, but you should be able to tell if your problem is with the A/V not opening or if it's somewhere else.

Oh, and be careful doing that, if you snap the throttle open too fast, the bog might stall the motor.

 

What was done to it (or the rest of the engine) between those two events?

 

That's what I'm trying to figure out. I pulled my hanger and rods to write down what I had, and reinstalled them. It didn't run worth crap after that. But then again, I couldn't recall the last time I put it to the floor either.

I found one had come off the hanger. I corrected that, still the same. I swapped the DR rods for CH rods. NO change. I really don't think at this point the trouble is related to that change. I went about a month without driving the truck in the winter and possibly durring that time some sediment or crap has settled in the secondary circuit?

I am trying to retrace my steps, see what I may have done. I installed different advance springs which make it come in quicker, but since the thing will wind right up on the primaries under load I don't think it's ignition, I mean I can feel when I hit the secondaries in my foot due to a slight change of throttle tension and that is like turning the light switch off. Phhhhbt! SOunds like "bill the dead cat" from the old Bloom COunty comic strip when I punch it.

Eric

 

Fuel leanout. Could be a blocked passage on the secondary side
or one of the down tubes that picks up fuel in the main fuel down wells has fallen down. It is only pressed into the bottom side of the carb top. Could be a fuel delivery problem too. Bad fuel pump
plugged filter etc. Check all rubber hose on the pull side of the fuel pump. A soft one can collapse, shutting off the fuel flow.

 

Anyone want to guess what it ended up being?

-the bakelite cam on the AV shaft that moves the link for the rod hanger up and down was broken! I took the carb apart and the thing fell in peices, I had a couple of parts carbs so I got the cam out of that.
NOW I have secondaries, nothing like the moan of two big 'ol throttle plates fully open! I still have a bit of hesitation and she doesn't climb like it should, but they are definitely working now and some adjustment of the AV tension and different rods and hanger may get it right!

Thanks everyone for you help!

Eric

 

Buy a Holley!!!!

 

If I'm going to spend money, I'll wait a year or so until I can afford Edelbrock's pro flo injection.

Until then, it's a good 'ol Rochester.

Eric

 

The secondary cam, huh? Well, I can't say that's the first time I've heard of that, but it's not that common. At least it was an easy fix!

 

hey eric i have the SAME problem!!
for some reason my secondaries arent opening.....i dont know how to do anything with the carb besides the A/V tension and i did that like a month ago and i just noticed this like a week ago...........when i floor it the secondaries open about a 1/8th of an inch......do u think i have the same problem?.....if so.....my bro knows a lot of stuff about holley's.....would he know how to change it out?

is there anything with vaccuums or other likages that may b messed up....everything is kept stock on the carb....choke and all that stuff


please help!!!

thanks

 

I don't think you have the SAME problem.
Mine were opening, just no fuel there when they did, big leanout.

Yours you say are opening just 1/8 of an inch? There has to be something going on there. CHeck the linkage on the passenger's side of the carb, pull off vaccum hoses etc if that's what you need to do in order to see it, DISCONNECT the throttle cable and operate the throttle manaully, see if they open.
If they do, it's your throttle cable adjustment. If not, look and see if the choke linkage is locking them out.

This lack of opening is definitley mechanical.

Eric

 

Glad to hear you got it running right again! That used to be a very common problem with early QJets, but later ones you almost never hear of the cam wearing out or breaking.

Enjoy "the call of the wild"- a Rochester 4bbl sucking amosphere through a dirty $4 KMart air filter! Buh...waaaaaaaaAAAAAAAAAAAA! Well, that's how I remember it from when I was 13. Still love it.

 

Mine's suckin' through a Wieand "flies eye" open element, and I need to replace it with a standard round open element.

The filter socks keep getting burn holes in them when it spits back through the carb, not that a Quadrajet with no choke will ever do that as you try to start it when it's 18 degrees out and you have to spend five minutes motorboating the footfeed to keep it gagging and sputtering until the manifold warms enough it will attain it's cammy 950 RPM idle.

Latah!

 

yah there must b something else wrong with mine
cuz today when i was goin to work it was running 220+ all the way even though i was doin 60 and its like 30* outside

and i could hear this rushing air noise from whenever the engine would rev and stuff.......i dont know if its a vacuum leak or the cat being clogged
i have been smelling a plastic kind of burning sensation lately when i park it after i drive it.....but i havent really had time to check that out