Quadrajet Adjustment Question

[DoubleDingo]

I have a feeling you have a vacuum leak somewhere

 

[Godwinaustin]

I have a feeling you have a vacuum leak somewhere

I would think that too , but I didn’t have a high idle until I started messing with the idle screws and vacuum lines

 

[DoubleDingo]

With it idling high and only pulling 15 on the vacuum gauge, something is amiss.

 

[bedwards]

Looks like to me your missing the vacuum actuator that pulls the choke off when warm and actuates the secondaries. That is where the port on the rear bottom goes to. I don't see how the secondaries are coming in without it. Goes where your first green circle is.

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[Godwinaustin]

Interesting .... Well My carb does have a brake actuator , but it is on the opposite end towards the front of the car ... although the schematic indicates it’s on the side closest to the firewall ... it IS missing the brake linkage which I ordered yesterday. That one definitely interacts with the secondaries but I thought it was independent of the choke ...

I disconnected all other vacuum sources... the diverter valve , the ege system , and vacuum driven throttle solenoid and actuator ... right now only vacuum I’m running is ported vacuum to the distributor.

Doing all that richened the mixture from what I can tell and slowed the idle down

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[Godwinaustin]

Also ... I thought the choke disengaged through the thermal metal coil releasing in the choke mechanism and didn’t require vacuum to disengage

 

[Rusty Nail]

I would think that too , but I didn’t have a high idle until I started messing with the idle screws and vacuum lines

Lmao

 

[Rusty Nail]

Haha ya don't say!

Pretty funny.
I have NOT been following this thread but since you are here, i'll take a look n see if I can help. I started fixing cars in the early 90s and learned in the GM C3 system.

Pretty sure the EFE valve defaults open (it has a spring) and is closed via vacuum through the thermostatic switch on the thermostat housing SO after the engine warms up, vacuum should not be present there.

That sure sounds good at least.

Same thing with the air cleaner. Default OPEN at operating temp.
Vacuum pulls it closed when cold.

After the thermostat gets hot enough, the pintle rises in the switch, blocking vacuum.

It's actually quite brilliant.

That just made me wonder if you are chasing a vacuum leak - that comes and goes, which is completely possible but again, I haven't read this thread.

 

[DoubleDingo]

Haha ya don't say!

Pretty funny.
I have NOT been following this thread but since you are here, i'll take a look n see if I can help. I started fixing cars in the early 90s and learned in the GM C3 system.

Pretty sure the EFE valve defaults open (it has a spring) and is closed via vacuum through the thermostatic switch on the thermostat housing SO after the engine warms up, vacuum should not be present there.

That sure sounds good at least.

Same thing with the air cleaner. Default OPEN at operating temp.
Vacuum pulls it closed when cold.

After the thermostat gets hot enough, the pintle rises in the switch, blocking vacuum.

It's actually quite brilliant.

That just made me wonder if you are chasing a vacuum leak - that comes and goes, which is completely possible but again, I haven't read this thread.

Possibly chasing a vacuum leak, and possibly the wrong carb for the application, and/or wrong schematic on the air cleaner.

 

[Rusty Nail]

I really didnt want to start in this thread..I don't know this guy..

How the hell does one overcook spaghetti?

Its all mushy and gross.
The spaghetti.

Who else is reading this thread?

Huuuuuuuuuuuh

He's got pix and everything.
Damnit man!

We need a tunes.

Here!
**** ill read it.
Let the Reverend play though or im out.
Can.not fix cars without MUSIC.
(sry boss) turn the radio back on.

xc_hide_links_from_guests_guests_error_hide_media

 

[Rusty Nail]

See?

Omg ported or manifold vacuum again..

It kind of depends.

I think '87 is a pretty smart cookie and I concur mostly with his above post.

Do NOT adjust the entire engine without the idle screw being in play. Everything after that will be wrong and it will NEVER run right.

Make a turns' worth or so of contact AND THAT is THE baseline. Adjust everything else around that.

Sounds good.

Look, you can look down the carb bore and SEE when it begins effect. Use your on-site judgement.

Idle is WAY TOO HIGH at 14°.
Truck was sold new at 0° most likely...

If you cannot get to zero, then turn mixture. screws, NOT the idle screw.


Omg! Forty tear old trucks have too many variables to fix over the internet..valve stem seals play too much of a role...engine condition yeah, but it's really in the heads. The valve seals...

We're gonna need more pictures.

I adjusted a truck around an incorrect diagram once (on this MSB)

Pay it ZERO ATTENTION.

Internet search until you are convinced you are not being led astray.

THAT is good advice junior.

Ensure correct picture, introduce the idle screw, reduce the igniton timing and you'll be on the right foot to a more correct tune up.

Post back here and we can go some more but we MUST estabish a proper baseine FIRST.

 

[Rusty Nail]

P.S.

Mushy spaghetti is much better cold.
Thanks?

 

[Godwinaustin]

Thank you ! That’s good advice on the idle screw I’ll turn it in and reduce timing if necessary ... also need to replace the vacuum brake linkage

 

[Rusty Nail]

Yeah... big ass vacuum leak needs capped. That is manifold vacuum yes?

At or below the line of the throttle blades is fill time or manifold vacuum. Above that is considered timed or ported vacuum which mechanically varies with RPM. (In the front) Likely makes no vacuum at idle. But the one pictured is low boy full time. (In the back) Makes a big ass noise - only if the engine is running though.
Can you not hear that? and looks like the CHOKE PULL-OFF is missing too but it's not terribly important right now.

That vacuum leak must be fixed.

Idk what a vacuum break is and admittedly did not look at the pictures OR read it all.

Hell, there are no vehicle specifics given and there's no reason to ask really, they are all pretty much the same - it doesn't what it's in LOL.

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[HotRodPC]

The vacuum break is actually a choke pull off. It's purpose is to pull the choke butterfly open to overcome the choke bi metal spring if you get on the skinny pedal. You obviously don't need the full choke on if you're well off of idle and trying build speed. You don't want to be to rich in that type situation. As soon as you're off the trottle, then the bi metal springs takes over again and allows the choke butterfly to bring the choke butterfly closer to closed until the engine is warmed up. And NO, not all carbs have it either.