Gas Grade Opinion Help....

[wagonman]

Hey Calidude the adjustment screw you are talking about is an idle air bleed.It is used on calif emission carbs and some 49 state units.It is a fine adjustment to get the mixture controll dwell in spec.I have all the tools to do these carbs as I am a GM dealer tech.I worked on those units when they were new.PM me back and I will give you my phone # and can walk you through.Or you can come to Reno.

 

[89Suburban]

Nice to see a tech in here!

 

[DesertBob]

Mine had a twitchy idle and I adjusted the mixture screws using the Vacuum Gauge method and it now idles smooth as silk. Before that I did all the vacuum hoses, cleaned the EGR and replaced the Cap, Rotor, Wires, Plugs and PVC valve and it still idled poorly. I had tried adjusting the mixture by RPM and could never get it right. Now the truck runs like it has Fuel Injection. I am very happy and have become a new fan of the QuaraJet. Damn thing idles at 600rpm and I can idle around in 2nd gear (4 speed with Low so I guess that is 3rd on other transmissions) and it still pulls strongly and smoothly when gassed.

 

[HotRodPC]

Mine had a twitchy idle and I adjusted the mixture screws using the Vacuum Gauge method and it now idles smooth as silk. Before that I did all the vacuum hoses, cleaned the EGR and replaced the Cap, Rotor, Wires, Plugs and PVC valve and it still idled poorly. I had tried adjusting the mixture by RPM and could never get it right. Now the truck runs like it has Fuel Injection. I am very happy and have become a new fan of the QuaraJet. Damn thing idles at 600rpm and I can idle around in 2nd gear (4 speed with Low so I guess that is 3rd on other transmissions) and it still pulls strongly and smoothly when gassed.

Way to go there Bob. I like hearing someone out there is still adjusting carbs the old fashioned way which IMO, is the right way. Using a vac guage. But, if you happen to live in an emissions state that puts the tailpipe sniffer in the tailpipe, then they start jacking with the adjustments to bring emmisions down and then it'll run like hell again in many cases.

 

[CaliDude76]

Way to go there Bob. I like hearing someone out there is still adjusting carbs the old fashioned way which IMO, is the right way. Using a vac guage. But, if you happen to live in an emissions state that puts the tailpipe sniffer in the tailpipe, then they start jacking with the adjustments to bring emmisions down and then it'll run like hell again in many cases.

Thats exactly what happened to me.. when they tested my truck.... whats this about the vacuum gauge testing? How do you do that, and where can I get one.... would LOVE to get my carb all adjusted right....!!!

 

[HotRodPC]

Thats exactly what happened to me.. when the ****** my truck.... whats this about the vacuum gauge testing? How do you do that, and where can I get one.... would LOVE to get my carb all adjusted right....!!!

Basically, many guys will use a tach to adjust their carb and get the RPM's high as possible and turn down the idle once they get it set as high as possible. Or turn the screws in and out til they hear the stumble or RPM's drop, then find the center of the 2 settings and call it good.
Using a Vac guauge, you are adjusting to get the vacuum as high as possible at idle regardless of the rpms. Then once you get the vac set as high as you can possibly get it, adjust your idle rpm with the idle screw. And sometimes you will go back and forth to the mixture screws and idle screw. But you want the highest vac reading possible at your set idle RPM in park. I have even seen some old timers do it with vehicle in drive and E brake on. Maybe Bob has a better explanation. I never consider myself good with carbs at all. I know some guys that seem to set them right on a nats ass by ear and occasionally smelling the exhasut. I sure can't. Guage or forget it for me.

 

[CaliDude76]

Basically, many guys will use a tach to adjust their carb and get the RPM's high as possible and turn down the idle once they get it set as high as possible. Or turn the screws in and out til they hear the stumble or RPM's drop, then find the center of the 2 settings and call it good.
Using a Vac guauge, you are adjusting to get the vacuum as high as possible at idle regardless of the rpms. Then once you get the vac set as high as you can possibly get it, adjust your idle rpm with the idle screw. And sometimes you will go back and forth to the mixture screws and idle screw. But you want the highest vac reading possible at your set idle RPM in park. I have even seen some old timers do it with vehicle in drive and E brake on. Maybe Bob has a better explanation. I never consider myself good with carbs at all. I know some guys that seem to set them right on a nats ass by ear and occasionally smelling the exhasut. I sure can't. Guage or forget it for me.

oh ok.. I see where your going with that.. but can you tell me what numbers...and where to hook the gauge up at?.... Sorry.. but I'm a novice at this, and would love to learn how to do it right... So I won't go and get hosed at a shop... they tell me 150$ and up, to get it all dialed in

 

[HotRodPC]

Oh its been so long since I adjusted one that way now CD, I'd be lying to give you a #. Maybe we can sweet talk DBob into to doing us a Tech thread on how to adjust a carb using a Vac Guage. That would be way cool.

 

[CaliDude76]

Oh its been so long since I adjusted one that way now CD, I'd be lying to give you a #. Maybe we can sweet talk DBob into to doing us a Tech thread on how to adjust a carb using a Vac Guage. That would be way cool.

Yeah... no kidding, Maybe if I wait and be patient long enough someone will have empathy and do it...LOL

It sux around here.. because all the shops really don't have any good guys anymore that wanna mess with these old carbs, or even know how, for that matter.
If they do... they wanna make a killing out of it.. it's nutz
So.. I just do it myself... or try like heck to figure it out

 

[Irishman999]

Hey Calidude the adjustment screw you are talking about is an idle air bleed.It is used on calif emission carbs and some 49 state units.It is a fine adjustment to get the mixture controll dwell in spec.I have all the tools to do these carbs as I am a GM dealer tech.I worked on those units when they were new.PM me back and I will give you my phone # and can walk you through.Or you can come to Reno.

I would say call this dude and ask him about the air valve.

 

[HotRodPC]

Yeah... no kidding, Maybe if I wait and be patient long enough someone will have empathy and do it...LOL

It sux around here.. because all the shops really don't have any good guys anymore that wanna mess with these old carbs, or even know how, for that matter.
If they do... they wanna make a killing out of it.. it's nutz
So.. I just do it myself... or try like heck to figure it out

It just be your calling in Cali. You're right the techs now want an idiot light or code reader to tell them what is wrong then charge you to replace the 10 things it can be associated with that code.
You learn to adjust carbs, and word of mouth, and charge $50 to set timing and carb, is alot cheaper than some techs like you said will dial in your mixture screws for $150.
I have not read this article, but it might be a good one. Read thru it and see what you might learn from it. I'll read it when I get a chance shortly.

http://www.chevyhiperformance.com/howto/45638/index.html

 

[DesertBob]

Here is what I did.

1. Warmed up the truck to make sure that the choke was fully open.
2. Connected up the engine meter so I could track RPM.
3. Set the carb mixture screws to 2 1/2 turns out. Next I set the idle to 600rpm and timed it at 8* BTDC at idle. Then I made sure that idle was still 600 rpm.
4. Connected the Vacuum Guage to the port at the back of my carb. Do not use the same port as the Distributor. You want full vacuum at idle.
5. I started on the passenger side mixture screw. (BTW - I did purchase the carb adjusting tool from AutoZone.) I started to slowly turn the screw in/out watching the vacuum guage. You want to see the vacuum climb. Once I reached maximum vacuum I stopped.
6. Reset idle to 600 rpm
7. Started on the driver side and repeated steps 5 and 6.
8. Went back to pasenger side and repeated steps 5 and 6.
9. Went back to drivers side and repeated steps 5 and 6.
10. I stopped here. I guess you could continue but I reached a tick over 21 in lbs of steady vacuum which is just about perfect.
    

In all this process took maybe 1 hour. Truck went from 18 in lbs of vacuum to 21 in lbs of rock steady vacuum, now idles smoothly and even the choke works better. Like I said before it now drives like it has fuel injection. No hesitation or hickups at any RPM. All that said my QuadraJet is in good shape and the motor has only 150k miles on it.

 

[DesertBob]

BTW I run 89 Octane fuel and put a can of Sea Foam in it every 3rd tank.

 

[CaliDude76]

Here is what I did.

1. Warmed up the truck to make sure that the choke was fully open.
2. Connected up the engine meter so I could track RPM.
3. Set the carb mixture screws to 2 1/2 turns out. Next I set the idle to 600rpm and timed it at 8* BTDC at idle. Then I made sure that idle was still 600 rpm.
4. Connected the Vacuum Guage to the port at the back of my carb. Do not use the same port as the Distributor. You want full vacuum at idle.
5. I started on the passenger side mixture screw. (BTW - I did purchase the carb adjusting tool from AutoZone.) I started to slowly turn the screw in/out watching the vacuum guage. You want to see the vacuum climb. Once I reached maximum vacuum I stopped.
6. Reset idle to 600 rpm
7. Started on the driver side and repeated steps 5 and 6.
8. Went back to pasenger side and repeated steps 5 and 6.
9. Went back to drivers side and repeated steps 5 and 6.
10. I stopped here. I guess you could continue but I reached a tick over 21 in lbs of steady vacuum which is just about perfect.
    

In all this process took maybe 1 hour. Truck went from 18 in lbs of vacuum to 21 in lbs of rock steady vacuum, now idles smoothly and even the choke works better. Like I said before it now drives like it has fuel injection. No hesitation or hickups at any RPM. All that said my QuadraJet is in good shape and the motor has only 150k miles on it.

Thanks alot for that info!!!!!

I actually spoke to wagonman about adjusting my carb too... He pretty much told me the same thing... only difference is, he was suggesting I use a dwell meter while adjusting the carb. I don't have one right now.. but I do have a vacuum gauge. I'm gonna try that if I don't get a hold of a dwell meter. Just have to make sure exactly what port to hook it up at...

 

[HotRodPC]

Here is what I did.

1. Warmed up the truck to make sure that the choke was fully open.
2. Connected up the engine meter so I could track RPM.
3. Set the carb mixture screws to 2 1/2 turns out. Next I set the idle to 600rpm and timed it at 8* BTDC at idle. Then I made sure that idle was still 600 rpm.
4. Connected the Vacuum Guage to the port at the back of my carb. Do not use the same port as the Distributor. You want full vacuum at idle.
5. I started on the passenger side mixture screw. (BTW - I did purchase the carb adjusting tool from AutoZone.) I started to slowly turn the screw in/out watching the vacuum guage. You want to see the vacuum climb. Once I reached maximum vacuum I stopped.
6. Reset idle to 600 rpm
7. Started on the driver side and repeated steps 5 and 6.
8. Went back to pasenger side and repeated steps 5 and 6.
9. Went back to drivers side and repeated steps 5 and 6.
10. I stopped here. I guess you could continue but I reached a tick over 21 in lbs of steady vacuum which is just about perfect.
    

In all this process took maybe 1 hour. Truck went from 18 in lbs of vacuum to 21 in lbs of rock steady vacuum, now idles smoothly and even the choke works better. Like I said before it now drives like it has fuel injection. No hesitation or hickups at any RPM. All that said my QuadraJet is in good shape and the motor has only 150k miles on it.

That sounds good and like a well maintained enigne to be able to run that smooth at 150K. That's no big deal for the newer cars, but for these old trucks and the 2pc old small block motors, to running that good at 150K something is done right. 150K on one of those motors is considered high mileage. Not dead yet, but high mileage. I still think getting 200,000 K out of these old motors is certainl achievable and even 300,000 if well maintained and lots of highway miles.