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Old 03-08-2012, 10:53 AM
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lt1silverhawk lt1silverhawk is offline
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Hey cobalt and barry,

@ cobalt: Thank you for the picture. I thought I understood what you meant but not having the carburetor open made it difficult. I also saw the image you uploaded to your album (currently your last uploaded image). This helps!

As to the plugs, I remember you did mention during the last rebuild that they weren't very likely to leak. I dabbed epoxy over them as a precautionary measure at the suggestion of the video series I was following on Youtube for rebuilding Q-jets. But I have seen no leaking and will remove the remaining epoxy upon dis-assembly when I reposition the needle hook.

Originally Posted by barry425
You can use an oxy-acetylene welding tip cleaner to clean up the air bleeds. Just don't get too vigorous with it, since the tip cleaners are actually little round files and will take off metal.
Got it.

Originally Posted by barry425
I hope you sprayed the venturies to get them clean. they looked pretty nasty.
I did spray everything I could with the carb and brake cleaners, and then wiped it all down. I didn't pay any attention to the venturis buit I can give them more a more rigorous cleaning during dis-assembly.

Originally Posted by barry425
You must adjust your idle speed screw (there is only one and it is on the throttle linkage side of the carb) to get an idle speed of around 500-800 rpm, THEN adjust the idle mixture screws (2, one on each side of the primary float bowl) for "lean best idle". You do this by running them both all the way in, but don't make them tight as you will damage the seat.
Next, with the engine off, turn them both out 3 turns (for a Quadrajet, 1 and 1/2 turns for a Carter).
Start the engine and check the idle speed. Turn the 2 idle mixture screws in or out as needed to make the engine run faster. Turn each one only 1/4 turn at a time, and make sure that they both are the same number of turns out.
Once you have the fastest idle with these two screws, go back to the idle speed screw and reduce the idle back to 500-800 rpm.
Generally speaking, once the idle mixture screw have been set in this manner, they might need only 1/2 turn in either direction to prevent a lean spot just off idle (assuming that the accelerator pump is working correctly).
Again, make sure that you only turn the mixture screws 1/4 turn at a time, turning first one and then the other so that they are both the same number of turns out. If they come out different, then you have a vacuum leak.
Thank you, this helps me a lot. As to the vacuum leak, based on the responses of a couple of members, I am suspecting that I didn't do a good job of sealing the intake manifold gasket on the passenger rise (the plugs came out more fouled on that side than the driver side). There also been some smoke coming out that side at times as well.

Originally Posted by barry425
If your idle is set over approximately 1,000-1,200 rpm, then your engine will diesel (run on after shutting the ignition off). This is VERY bad for the bearings!
That's good to know! Unfortunately the tach in the truck doesn't seem to be very accurate so I'll be using the RPM readings provided by the timing light (timing light shows about 200 rpm higher than what the tach registers).I did adjust the idle speed screw a few days back and it seems to be hovering around 750 rpm once at operating temperature.

Originally Posted by barry425
Set the timing now.
That is the next step. I did being work on a timing tape. Just need to find time to sit down carefully make the markings. I'm thinking that it doesn't need to be big enough to go all the way around (full 360 degrees). Maybe up to 60 degrees before and after TDC (180 degrees) should be sufficient. Any thoughts?

Originally Posted by barry425
After setting the timing, you may have to increase or reduce the idle SPEED screw, but don't touch the 2 mixture screws again unless the engine has a lean bog or miss just off idle.
Good luck.
Got it. I have the screws at four full turns out right now and will leave them be for the moment.

Hopefully by this Friday evening, I will disassemble the carb, clean up the venturis some more and reposition the needle hook into the correct position. Saturday morning I start working on the timing. I will report back as regularly as I can.

Thanks for the continued help!
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