Rochester carb help possible bad linkage
 

66 burb
454 out of 75 el camino
700r4 tranny
np203 t case
rochester quadrajet

Hello all,

I've been watching all the videos around the bogchester trying to figure out why my secondaries wont open.

Ive adjusted the setting on the right to make sure the top flaps snap back nicely and Ive made sure the electronic choke is working correctly and when warmed up the little stopper on the passenger side is moved away properly and not blocking the shaft from rotating.

Last night I took a flat blade screwdriver and after the truck was well wamrd up I turned the shaft on the secondaries manually and they opened nicely and the car revved perfectly with no sputter.

So I'am thinking now that my linakge is all wrong. (PO set up) and I think modified to get the 700r4 tv cable set.

Looking at the linkage I don't see how the accelerator can actuate the rear shaft that controls the secondaries. I see the bar that connects the two but when I throttle down it does not move.

Ill take a pic and post today. f anyone has a similar setup I would love to hear or see how yours it set.

The car runs and starts perfectly just bogs out when I mash it.

thanks

Kris

Re: Rochester carb help possible bad linkage
 

So the black tab on the linkage that connects tot the rear shaft doesn’t move when the throttle is moved. I can move it manually but nothing seems to touch it when the gas peddle is pressed.
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Re: Rochester carb help possible bad linkage
 

A better pic would help.
From the side directly over the valve cover.

Re: Rochester carb help possible bad linkage
 

I think you might be giving conflicting information. On the one hand you are saying the secondaries are not opening and on the other the car runs and starts perfectly, just bogs down when you mash it, which kind of indicates the secondaries are opening fully when they shouldn't.

I'm new to the world of quadrajets but with just having gotten mine going I've noticed a thing or two. Mine used to cough and spit whenever I put the throttle to the floor. That was with the HEI directly connected to a port in the intake manifold. Since then I hooked the line to a port at the base of the carb passenger side between the fuel inlet and the choke. No more of the funny stuff and last time I had it out I believe the secondaries to be coming on when needed. This is just an observation that may or may not have merit, as I was also playing around with the timing.

I had put a kit in mine and from what I learned at the time the secondaries should not open until the demand is there.

Re: Rochester carb help possible bad linkage
 

the quadrajet was designed to run of the primary smaller barrels as a fuel and emissions saving deal. So when I say it runs fine it does. It runs just like a fat heavy dog though like I had a two barrel carb on a giant 454.

When I mash the peddle is when I guess its less of a bog and more like nothing happens. If I go easy on the throttle it then it runs just fine and I can cruise around no problem. BUT There is definitely no secondary's opening.

So runs/idles/revs just fine on the 2 primary's. + I can manually engage the secondary's at idle and it revs fine.

However, I cannot see a way that the throttle setup can move that middle black tab. It just sort of rotates there. I can manually move that black tab and the secondary's move.

How to get the throttle to move the secondary's is the question.

Ill get more pics tonight.

Also there is a port on the front driver side that is not hooked up to anything nor plugged. Any idea what that is for and should it be plugged?

My efi is hooked up to the carb as well and not the manifold.

Re: Rochester carb help possible bad linkage
 

here is another pic

Re: Rochester carb help possible bad linkage
 

ok I circled in black what I am referring to.

the black tab is connected via a rod to the secondary shaft.

So when the throttle is turned via pedal or hand. this tab does not move at all so is not actuating anything.

In yellow I circled this little pin, Is that supposed to hit the black? It seems bent maybe??

Re: Rochester carb help possible bad linkage
 

That open port is ported vacuum. Put a cap on it. It’s a vac leak once the throttle opens a bit.
That yellow circled pin is normal. It’s the bottom end of the accelerator pump linkage. It doesn’t contact anything.
There should be an arm that contacts the secondary linkage (black circle)when the primary is opened about halfway. It looks like yours has been modded to hook up your tv cable.

Re: Rochester carb help possible bad linkage
 

So when your throttle is fully depressed the secondary linkage also works through the spring on the drivers side but it is not opening the plate, correct? I just tried mine and the only way I can get the secondary to open is by pushing fully down on that green thing connected to the choke linkage. That vacuum pot at the back on the passenger side I don't even have a line to so I probably don't have the secondaries either.

Re: Rochester carb help possible bad linkage
 

Where does that second arm hook up to the secondary linkage?

Have a pic by chance?

Re: Rochester carb help possible bad linkage
 

so that green thing connected to the secondary linkage is there by design. when your choke is engaged it too is engaged stopping the secondaries from opening when the engine is not warm enough...another emissions things added....once your car is warmed up and the choke goes off then that green thing should move out of the way automatically...let the car warm up and see if it does...I thought it was an issue too but once I let it idle awhile it did exactly that.

Re: Rochester carb help possible bad linkage
 

I bin lookin’!
Try this.
Pic off bottom side in idle bypass section shows two arms.

https://www.crankshaftcoalition.com/...4MV_carburetor

I’ll look for more.

Look in here in quadrajet listing.

https://www.carburetor-parts.com/Car...ls_ep_274.html

Re: Rochester carb help possible bad linkage
 

Not emissions thing.
Safety thing.
Keeps you from opening secondaries on a cold engine.
Also helps your wallet!
Keeps the money in there instead of needing to replace your blown up motor if you worked it too hard when cold.

Re: Rochester carb help possible bad linkage
 

Here is a pic of how your throttle linkage should connect. The metal tab combined with the switch inside the black bellows is the kick down for a TH400. The TV cable for the 700r4 may screw things up.

The pin where your spring is currently looped around should unbolt or unscrew.

Re: Rochester carb help possible bad linkage
 

Picture of lock out lever on passenger side behind choke pod.

Picture of green lever that moves the black secondary arm.

Let me know if you need any more pictures.

Re: Rochester carb help possible bad linkage
 

Good pics Ron!
If he put up a pic or two like your 2nd and 3rd ones I bet we’d see what he’s missing or is installed wrong.

Re: Rochester carb help possible bad linkage
 

Might be wrong but I don’t see any thing wrong with the secondary linkage in OP pictures. Remember the linkage can push the secondary lever toward the firewall and if the shaft is locked out the shaft wont move because of the spring. That is what that coiled hairpin looking spring is for.

I think the problem is going to be on the choke side.

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I’ve looked at a bunch more videos and I don’t see where the issue is either. I’ll start messing with the chicks side and see if I can get it to go. Thanks for the suggestion

Re: Rochester carb help possible bad linkage
 

If you look on Ron’s pics you’ll see that vertical green tab. It’s part of the primary linkage.
Just to the right of it is another tab pointing to the back. It’s part of the secondary linkage.
When you open the primary the green tab contacts the other tab which starts the secondary linkage moving.
I think your secondary tab has been modded to fit your tv cable. Likely removed.
That’s why I suggested a pic from straight above like Ron took.

Re: Rochester carb help possible bad linkage
 

Here are two pictures with the throttle linkage fully open.

Notice on the first picture the hairpin spring is horizontal in the slot of the green secondary shaft. This shows that the secondary shaft is NOT open and that just the springs are wound up attempting to open them.

The second picture shows the hairpin spring and the slot in the green secondary shaft is now vertical showing the secondaries are open.

Just truing to help sometimes a picture is better than a video.

Re: Rochester carb help possible bad linkage
 

Ok thanks, that green tab is def not there so that is obviously the missing link. I’ll take a pic from top down this afternoon and post up hopefully there is a way to get this to work. Worst case finding another donor Rochester shouldn’t be too hard and then order the proper kit to add the tv cable

Re: Rochester carb help possible bad linkage
 

Ok, messed around with the linkage.

Removed the return spring and the accelerator cable rod to free the linkage up.

NOW when I turn the linkage the secondary engages.

So I’m thinking the accelerator connector rods need proper geometry adjusting as when im using the pedal or my hand to rev the engine the linkage doesn’t allow enough travel


God I hate previous owners.

Re: Rochester carb help possible bad linkage
 

You are 100% correct sir!

Thanks

Ok now I see where the hold up is!!

The return spring is hitting the accelerator rod blocking the full travel.

That’s the golden ticket!

I’ll mess with the setup and let you guys know

Re: Rochester carb help possible bad linkage
 

Ok in the home stretch here.

This entire issue is simply (but not so simply right) in the accelerator and return spring geometry.

I've posted some pics.

You can see how the accel rod is hitting the return spring holder.

I've moved the return spring to the lower arm and attached it to a bolt on the manifold.

The stud there where the spring was attached is still in the way and it is a pressed fitting. I was hoping just to unscrew it.

So cut it off? or get a longer accelerator rod and bend it so the two don't hit?