Quadrajet Adjustment Question

[AuroraGirl]

17.5 is good vacuum. It's right in the middle of the "green" on my vacuum gauge. If you have access to your grandpa's gauge use it.

Its broken, fell on the ground and the glass broke in a corner and the rubber hose was torn.

 

[AuroraGirl]

17.5 is good vacuum. It's right in the middle of the "green" on my vacuum gauge. If you have access to your grandpa's gauge use it.

Its broken, fell on the ground and the glass broke in a corner and the rubber hose was torn.

Also, I was asking if its inches of mercury, im assuming yes by that

 

[Rusty Nail]

It is.

Prolly still works too.

Hotrod I know what a pull-off does but vacuum break is not the word chevrolet uses, I was being a dick. Thats what ford call it or something.

 

[HotRodPC]

If I'm not mistaken, in this example of pics here, you're missing a rod from the vac break to the secondary top butterflies. They can't open to let air in. The bottoms ones on the throttle shaft are probably opening to let fuel in, but doesn't do much good if you can't add air to the fuel. Biggo waste of raw gas and no power advantage if you can't get air down there with the gas.

 

[DoubleDingo]

Its broken, fell on the ground and the glass broke in a corner and the rubber hose was torn.

Also, I was asking if its inches of mercury, im assuming yes by that

Yes it is inches of mercury. I bet that gauge still works/worked. A new hose can do wonders.

 

[HotRodPC]

It is.

Prolly still works too.

Hotrod I know what a pull-off does but vacuum break is not the word chevrolet uses, I was being a dick. Thats what ford call it or something.

I thought I was explaining to OP. But GM actually does use it too sometimes.

 

[HotRodPC]

It is.

Prolly still works too.

Hotrod I know what a pull-off does but vacuum break is not the word chevrolet uses, I was being a dick. Thats what ford call it or something.

In Fact, look at the emissions sticker on the air cleaner. Secondary actuator break.

 

[AuroraGirl]

Yes it is inches of mercury. I bet that gauge still works/worked. A new hose can do wonders.

No, like, it was broke off a piece of the corner and was open, and the hose was bad, but it cant pull vacuum with... well... a hole to the atmosphere. we threw it away long ago. And it didnt have a readable face, either, just tape that said good.
im not sure what was going on with it, but I just have yet ot buy one.

 

[Rusty Nail]

In Fact, look at the emissions sticker on the air cleaner. Secondary actuator break.

Great!

You can take over for me here since you know so much about it.

I'm a *******.

 

[AuroraGirl]

You do not have to be hostile, I was asking because this has been referenced before and im asking for clarity of what you mean as charlie is not present. i didnt think it was for me direectly, no.

In Fact, look at the emissions sticker on the air cleaner. Secondary actuator break.

i would ignore his outburst. a grown man who feels that behavior at 2am is needed, welcomed, or warranted is not one we need to engage with.

 

[Godwinaustin]

If I'm not mistaken, in this example of pics here, you're missing a rod from the vac break to the secondary top butterflies. They can't open to let air in. The bottoms ones on the throttle shaft are probably opening to let fuel in, but doesn't do much good if you can't add air to the fuel. Biggo waste of raw gas and no power advantage if you can't get air down there with the gas.

this may explain why a small amount of gas came off with the vacuum cap I pulled on the back of the carb (the side where the secondaries are) either way I had noticed that linkage missing and have a new one coming Saturday.

I’ve noticed some quadrajets have two of those vacuum actuators but mine only has one

 

[Godwinaustin]

So I double checked base timing and it was at 12, I dropped it to 8 just to get the idle down but it’s still fast even with the idle speed screw all the way out.

ive concluded, after my own research and all the help here , that there has to be a vacuum leak somewhere. Guessing it’s the base plate. I loosened and retorqued those bolts to spec but still high so gonna replace that gasket next.

 

[Godwinaustin]

So I double checked base timing and it was at 12, I dropped it to 8 just to get the idle down but it’s still fast even with the idle speed screw all the way out.

ive concluded, after my own research and all the help here , that there has to be a vacuum leak somewhere. Guessing it’s the base plate. I loosened and retorqued those bolts to spec but still high so gonna replace that gasket next.

 

[75gmck25]

Since you don’t know the specs on your mechanical advance, you need to get the idle down to about 500-600 rpm to verify base timing. Even at 1000 rpm you might be starting to get some mechanical advance, and that would throw off your timing measurement.

Base timing of 8 degrees BTDC is very typical of a stock SBC, so it should idle well with that timing. Also ensure you have the vacuum advance line pulled off the distributor and the line plugged so it does not affect timing at idle. The debate about ported vs. manifold is irrelevant at this point since you will have both ports capped on the carburetor.

The rear choke pull off provides a short delay before it starts to pull the choke partially open. It’s somewhere around 5 seconds, but you can change the time by drilling out the orifice or changing the pull off. Until the engine is warm and choke fully open, the choke also prevents the secondary air flaps from opening.

Also check that the the 3/8” hose to the PCV is tight on the carburetor. Shake the PCV valve to make sure it’s loose inside and vacuum at idle can pull up the plunger inside and seal it off.

Bruce

 

[Godwinaustin]

Interesting comment on the pcv ... this high idle started after I replaced the gasket pcv valve and hose. I checked the seal to the crankcase , but I’ll recheck the hose and the valve itself.