Runability issue. Minor. Question.

[lyrikz]

I have a 1981 454 engine that was rebuilt with bigger cam/ different heads and i had the stock quadrajet rebuilt.

Issue im having is that it doesnt always idle. Some days it idles perfect all day. Other days, it idles fine at first then stops. I have to keep my foot on the gas.

Any thoughts???? Everything is hooked up fine. Why would some days it idle, then others it not??

[chevypoint]

Sounds like the choke is getting hung up. Check for vaccum leaks and to see if the linkage is rubbing on anything.

[geezer#99]

Primary throttle shaft is loose. Plates move sideways slightly and hang up on throttle bore. Changes your idle. I had one do the same. One of the little screws that holds the plate to the shaft was loose. Plate moved slightly.
Stroke the throttle by hand wide open and see if you can move the shaft side to side.

[lyrikz]

Originally Posted by geezer#99

Primary throttle shaft is loose. Plates move sideways slightly and hang up on throttle bore. Changes your idle. I had one do the same. One of the little screws that holds the plate to the shaft was loose. Plate moved slightly.
Stroke the throttle by hand wide open and see if you can move the shaft side to side.

Choke is moving freeely.

As for the throttle shaft, where is that located exactly? So open the throttle all the way, and then rock it back and forth to check for play?

I took the carb to a carb guy here in kirkland and right in front of me he tore the whole thing down, and put it all back together. Didnt mention anyhing about the shaft being lose. He put two small ball bearings into this two tiny holes and hammered them in. It idled fine for about ten mins then started to act up...

[crazy longhorn]

Originally Posted by lyrikz

Choke is moving freeely.

As for the throttle shaft, where is that located exactly? So open the throttle all the way, and then rock it back and forth to check for play?

I took the carb to a carb guy here in kirkland and right in front of me he tore the whole thing down, and put it all back together. Didnt mention anyhing about the shaft being lose. He put two small ball bearings into this two tiny holes and hammered them in. It idled fine for about ten mins then started to act up...

Take the return springs off the carb, turn it about 1/4 way open....then shake the shaft up/down(north /south)....you will find the slop in the throttle shaft That Geezer was talking about & I agree, that could be the issue. in that situation, the throttle plates do not set down in the same spot every time.This is a common problem on any 40yr old carb. Another Q , I might ask...to keep it running @ the light, does she load up(rop rop rop), before she stops? crazyL

[lyrikz]

Originally Posted by crazy longhorn

Take the return springs off the carb, turn it about 1/4 way open....then shake the shaft up/down(north /south)....you will find the slop in the throttle shaft That Geezer was talking about & I agree, that could be the issue. in that situation, the throttle plates do not set down in the same spot every time.This is a common problem on any 40yr old carb. Another Q , I might ask...to keep it running @ the light, does she load up(rop rop rop), before she stops? crazyL

Ok, so take the air cleaner off, remove the return spring, then open the throttle 1/4 of the way and then shake the shaft up and down... So i reach INSIDE the carb to get to the shaft ya? I will give it a shot.

Yes, it does. it does the rop rop rop die... If i dont put gas to it.


Geez, the carb was in really good shape when i took it off the factory engine. basically cleaned it up. Then put it on the truck. Well, i was getting that idle issue so i took it to a carb place. He took it apart and plugged these two holes on either side of the carb. I wish i knew wht they were called. lol. Sorry.

[geezer#99]

Well that makes it easy. A no brainer. Take it back to the guy who rebuilt it.
I don't know where he might hammer 2 small bearings into.
Primary throttle shaft is in the bottom plate of the carb. When you stroke the throttle it has the 2 primary plates attached to it. The plates can be seen if you look down into the carb when you stroke the throttle. Below the choke plate. If the shaft moves side to side the plates can hang up in the bore changing the idle rpm.
Can you take a pic of your carb pointing to where he put the bearings in.
Here's a pic of a carb that shows the bottom side. The round plates attach to a shaft which runs from side to side. The round plates can hang up sometimes. In the pic the top 2 are the primary. Bottom 2 are the secondaries. This isn't a quadrajet but looks similiar.
http://67-72chevytrucks.com/vboard/s...d.php?t=489059

[bigguy69]

mine was getting to much pressure. i had to put a regulator on it .

[geezer#99]

You can't reach inside. When you open the throttle just wiggle that part around to check for excess play. Up, down, sideto side. The throttle arm on the drivers side that the return spring is attached too is what you need to move around.
You don't need to know what the holes are called. We just wonder where they were located. Top or bottom. Inside, outside??

[lyrikz]

Originally Posted by geezer#99

You can't reach inside. When you open the throttle just wiggle that part around to check for excess play. Up, down, sideto side. The throttle arm on the drivers side that the return spring is attached too is what you need to move around.
You don't need to know what the holes are called. We just wonder where they were located. Top or bottom. Inside, outside??

Ok, i wiggled that and it feels REALLY solid. BUT, i had the return spring still hooked up.. i will try that again.

As for the holes. He took the whole carb apart and they were at the bottom. Says its very common and he does it to every quadrajet. It was INSIDE the carb near the front or the back. HOles were evenly spaced.

This guy owns carb connection in kirkland. He basically pulled the carb off, took it all apart, shook everything down, checked everything for play, popped two bb's in those two holes and put it back together. But, it still did the same thing. If i cant find any play or vacuum leaks (he couldnt find a vacuum leak either) then i will take it back i guess.

I am running a pcv if that matters at all??? I will get some pics of the carb and post em.

[geezer#99]

Very little side to side movement can make it hang up. Where's your return spring hooked to? The spring could be pulling it sideways.
I checked your build thread. Spring to the back. Try hooking it up so it pulls straight forward. Spring in front.
Hooked to the back like yours might not be pulling it shut consistently.

[lyrikz]

Originally Posted by geezer#99

Very little side to side movement can make it hang up. Where's your return spring hooked to? The spring could be pulling it sideways.
I checked your build thread. Spring to the back. Try hooking it up so it pulls straight forward. Spring in front.
Hooked to the back like yours might not be pulling it shut consistently.

Geez, today when i get home, i will snap multiple picks around the carb so you can see.

Just to recheck, when checking for vacuum leak, get some carb spray, and with the vehicle running, you spray it around the base of the carb and if you get any idle pickup there is a leak somewhere.. The carb guy did that once before and nothing, but im willing to recheck. ahah...

[lyrikz]

Originally Posted by geezer#99

Very little side to side movement can make it hang up. Where's your return spring hooked to? The spring could be pulling it sideways.
I checked your build thread. Spring to the back. Try hooking it up so it pulls straight forward. Spring in front.
Hooked to the back like yours might not be pulling it shut consistently.

Ok, here we go. I have video. lol. Take a peek, let me know what you think.. One pic has some text on it.

Click this pic for video.

[geezer#99]

Geez Man!!! You take awesome pics!!!
The movement side to side would be enough to hang up the plates in the bore. Up, down is minimal. Shaft bushings appear good. The pic with the writing on it is your secondary lock out. THat movement might effect your changing idle but I suspect it's the side to side of the primary that's your problem. WE'll try the front first.

I'd move your return spring around so it's pulling from the front. Hook one end into that hole just below the cable hookup. You could make a temporary bracket that can be bolted down to one of your intake or valve cover bolts. A tall L-shaped bracket would work. Set it up to pull straight ahead. If that cures it you can get some nicer brackets on Summit.
Once we get that figured out we're gonna get you too replace that piece of rubber fuel line with a new complete steel tubing line. That rubber line is a big fire waiting to happen.

[lyrikz]

Originally Posted by geezer#99

Geez Man!!! You take awesome pics!!!
The movement side to side would be enough to hang up the plates in the bore. Up, down is minimal. Shaft bushings appear good. The pic with the writing on it is your secondary lock out. THat movement might effect your changing idle but I suspect it's the side to side of the primary that's your problem. WE'll try the front first.

I'd move your return spring around so it's pulling from the front. Hook one end into that hole just below the cable hookup. You could make a temporary bracket that can be bolted down to one of your intake or valve cover bolts. A tall L-shaped bracket would work. Set it up to pull straight ahead. If that cures it you can get some nicer brackets on Summit.
Once we get that figured out we're gonna get you too replace that piece of rubber fuel line with a new complete steel tubing line. That rubber line is a big fire waiting to happen.

Ok, so dont have the return spring behind it, you want it in front of it??? If that does not take care of it, whats the next fix?

That fuel line was supposed to be temporary... Putting it on my fix list now.

[geezer#99]

Try it in front first.
Next fix could be pulling carb off, flipping it over, modifying the plate or limiting side to side movement. All the things you might not be familiar with.
The ones I fixed by just moving the spring helped.
If you need to talk it over pm your number.

[lyrikz]

Originally Posted by geezer#99

Try it in front first.
Next fix could be pulling carb off, flipping it over, modifying the plate or limiting side to side movement. All the things you might not be familiar with.
The ones I fixed by just moving the spring helped.
If you need to talk it over pm your number.

I will give it a try... To get it to happen i have to drive it say for 5 miles or 10 mins or so.. Shut it off for awhile, then drive again.. Then it wont idle. If i have time tonight i will try that... hope its as simple as that.

[lyrikz]

Originally Posted by geezer#99

Try it in front first.
Next fix could be pulling carb off, flipping it over, modifying the plate or limiting side to side movement. All the things you might not be familiar with.
The ones I fixed by just moving the spring helped.
If you need to talk it over pm your number.

Ok, more info. This is just BAFFLING the hell out of me.

So that throttle you were talking about is good. Changed all that stuff you said and its good to go.

here is the situation. Start the truck up and it runs ok when its cold. As it warms up it runs fine but it just does not want to idle. BUTTTTT, pay attention to this part. If the truck is fully warm, and when i pull up to a light and i let it DIE by itself, then restart it, the issue doesnt come back. WTF!!!

Also, the damn thing when you start it cold, just doesnt start well at all. I think there is something messed up with the choke. I might get rid of the electric and go manual or something.

So what do you think. Why when its fully warm not want to idle. But the first time you let it die by itself. Then restart, it idles great for however long you want it to????

Thoughts?

[lyrikz]

Originally Posted by lyrikz

Ok, more info. This is just BAFFLING the hell out of me.

So that throttle you were talking about is good. Changed all that stuff you said and its good to go.

here is the situation. Start the truck up and it runs ok when its cold. As it warms up it runs fine but it just does not want to idle. BUTTTTT, pay attention to this part. If the truck is fully warm, and when i pull up to a light and i let it DIE by itself, then restart it, the issue doesnt come back. WTF!!!

Also, the damn thing when you start it cold, just doesnt start well at all. I think there is something messed up with the choke. I might get rid of the electric and go manual or something.

So what do you think. Why when its fully warm not want to idle. But the first time you let it die by itself. Then restart, it idles great for however long you want it to????

Thoughts?

Well, i figured out one issue. So as i was staring at the carb, and the truck was idling. I covered with my hand the little top choke butterfly, and the rpms smoothed out and the engine rpm increase. I have a vacuum leak in this engine somewhere. So, i picked up a propane bottle and am going to go find the leak. Let you know once i have this figured. Think its weird the carb guy would miss somehting so obvious.

[geezer#99]

So when you closed off the choke butterfly was the motor warmed up or still working on the choke.

[D.PASSMORE]

You could have a slight lean condition in the main jets - might not big enough. The main jets control the amount fuel that is pulled through the idle circuit. You can tell if it is lean by adjusting the idle mixture screws. If you don't get a noticeable response then its lean. Don't get the main jets confused with the metering rods - the metering rods control flow for cruise and response. I went through the same issue (all the above troubleshooting) and finally upped the size of the main jets in the Q-Jet carb and it runs fine. Took alot of reserch and reading but, I gained alot of base knowledge.

[lyrikz]

Originally Posted by geezer#99

So when you closed off the choke butterfly was the motor warmed up or still working on the choke.

Yes, it was fully warmed up when i coverd that area and idle smoothed out and raised up quite a bit.

[geezer#99]

OK!!
Along the lines of D. Passmore's post. Maybe your metering rods are hanging up on the gasket. Runs lean cause they're stuck down in the jets.
Here's a link on quads. Lots of info.

http://www.digitalcorvettes.com/foru...ad.php?t=88376

[lyrikz]

Originally Posted by geezer#99

OK!!
Along the lines of D. Passmore's post. Maybe your metering rods are hanging up on the gasket. Runs lean cause they're stuck down in the jets.
Here's a link on quads. Lots of info.

http://www.digitalcorvettes.com/foru...ad.php?t=88376

Geez, quick question on the electric chokes. When you are setting those up you have the low cam and the high cam idle right?

so, to get on the high cam, you crack the throttle and you can lift it to the high cam. Now, when setting the electric choke, when its dead cold, do i want the electric choke to where it will put it on the high cam idle??? Im trying to read on how to set this and not a whole lot of info.

Also, i used the propane to find that there is a slight vacuum leak at the throttle shaft, but it appears like that is a normal amount. Im starting to have a feeling that its running out of fuel at idle. when you cover the carb, the idle pops up a bit, then starts to die out. So i dont think there is a vacuum leak, i think its just lean. those two screws in the front of the carb are for idlemixture correct??

[D.PASSMORE]

Try this link too.

http://www.florida4x4.com/tech/quadrajet/index.php

Another indication was when you used your hand to cover the "area" and it smooth out is a maybe a tell sign that you need more fuel in the idle circuit.