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  #16 (permalink)  
Old 06-23-2012, 09:19 PM
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Quote:
Originally Posted by LEROYDOZOIS
so i was able to put 92 jets in the secondaries in place of the 95 jets.

the afr went from 13.3 up to 14.4 at 2000 rpm, and at 2500 rpm it went to 14.7__14.8

i did however buy a 4 hole spacer and im going to replace it with the open one i have now. thankyou guys for the info, ill let you all know how the adapter works out and what it changes. then well all have the extra info =]
You aren't running on the secondaries at that rpm/load- unless you're flooring it.

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  #17 (permalink)  
Old 06-23-2012, 10:13 PM
How fast is fast enough?
 
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First off, never tune your idle with an O2 sensor, use the vacuum signal. Next, are you running a distributor with vacuum advance? Next, what is the jet sizes you are currently using and rod step sizes? What position is your accelerator pump arm in?

How do you have your o2 sensor fitted? Wide band or narrow band? How old is it?

How do your plugs look? How are you calculating mileage?

At 6mpg on a stock engine I'm surprised you're not fouling plugs like crazy.

Is the entire surburban stock, like every last detail? How many miles? How is the leakdown?
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  #18 (permalink)  
Old 06-24-2012, 11:18 AM
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Quote:
Originally Posted by ap72
First off, never tune your idle with an O2 sensor, use the vacuum signal. Next, are you running a distributor with vacuum advance? Next, what is the jet sizes you are currently using and rod step sizes? What position is your accelerator pump arm in?

How do you have your o2 sensor fitted? Wide band or narrow band? How old is it?

How do your plugs look? How are you calculating mileage?

At 6mpg on a stock engine I'm surprised you're not fouling plugs like crazy.

Is the entire surburban stock, like every last detail? How many miles? How is the leakdown?

95 primaries>>> 75x47 rods>>> blue springs-3 hg>>>pump rod in middle hole
92 secondaries

i have the AEM wideband 30-4100 and its like 3-4 months old

i roughly guessed where my starting point was ( needle width under 1/4 tank ) then put 10 gallons in it and checked the mileage when it reached back to that point.

the motor is a 1985 marine motor squashed into the 1980 chassis. motor has no emissions at all hooked up on it. and i have the dizzy hooked up to the constant vacuum port. motor is healthy, no noise of any kind
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  #19 (permalink)  
Old 06-24-2012, 01:11 PM
How fast is fast enough?
 
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What vacuum are you cruising at? I'll go out on a limb and guess around 3"...

What is your initial and total timing? What vacuum advance canister are you using?
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  #20 (permalink)  
Old 06-24-2012, 01:57 PM
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The Edelbrock carb has multiple stages:

--Idle - only uses the idle passages if its operating correctly. Settings at this stage do not affect other operation, so just get the best idle possible.
Primary
-- Cruise mode - this is the thicker part of the primary rods (which are drawn down into the jet). For yours its the 75 area of the 75x47 rod. At normal operating vacuum the thick part of the rods will be pulled down and it should be operating in cruise mode. There must be enough vacuum to pull the rod down against the springs.
-- Power mode - When vacuum drops the springs push the rods up and you get the power part (47) of the rod in the jet. However, the spring stiffness must be matched to engine vacuum so that you prevent a bog or excessive richness. If it transitions to power mode too slowly you get a lean bog (I could see it on my AFR).
Secondary
Secondaries kick in based on vacuum and throttle position. The secondary rods and jets don't affect cruise and moderate power mode.

Also take a look down the carburetor throat while its running, using a mirror and flashlight. If you see any raw fuel on either primary barrel, you have a problem with the carb. My engine idled very badly and I could see raw fuel on one side and it turned out to be a shard of RTV that had been sucked into the carburetor. It was preventing air flow and making it run very rich.

If you are running an AFR of 13.5 at cruise that is not great, but it should not be dragging fuel mileage down that dramatically. Its also safer to run a little rich than it is to run too lean. At one point I had the 1406 running in the 15-16 AFR range during cruise, and gas mileage did not get any better. I finally gave up on the Edelbrock and rebuilt a Quadrajet.

I am running about that same 13.5 AFR with my Quadrajet, and the engine runs better than it ever did with my Edelbrock 1406. The throttle response and drive-ability is much better with the Quadrajet, but I have not had time to recheck gas mileage.

Bruce
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  #21 (permalink)  
Old 06-24-2012, 02:15 PM
How fast is fast enough?
 
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Yea, I ran the numbers and your calibration is fubar. Swap in the 7057 rods and a 6" spring.

Adjust your adle screws for max vacuum and leave the rest alone for now.
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  #22 (permalink)  
Old 06-24-2012, 07:24 PM
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im amazed...

Quote:
Originally Posted by 75gmck25
The Edelbrock carb has multiple stages:

--Idle - only uses the idle passages if its operating correctly. Settings at this stage do not affect other operation, so just get the best idle possible.
Primary
-- Cruise mode - this is the thicker part of the primary rods (which are drawn down into the jet). For yours its the 75 area of the 75x47 rod. At normal operating vacuum the thick part of the rods will be pulled down and it should be operating in cruise mode. There must be enough vacuum to pull the rod down against the springs.
-- Power mode - When vacuum drops the springs push the rods up and you get the power part (47) of the rod in the jet. However, the spring stiffness must be matched to engine vacuum so that you prevent a bog or excessive richness. If it transitions to power mode too slowly you get a lean bog (I could see it on my AFR).
Secondary
Secondaries kick in based on vacuum and throttle position. The secondary rods and jets don't affect cruise and moderate power mode.

Also take a look down the carburetor throat while its running, using a mirror and flashlight. If you see any raw fuel on either primary barrel, you have a problem with the carb. My engine idled very badly and I could see raw fuel on one side and it turned out to be a shard of RTV that had been sucked into the carburetor. It was preventing air flow and making it run very rich.

If you are running an AFR of 13.5 at cruise that is not great, but it should not be dragging fuel mileage down that dramatically. Its also safer to run a little rich than it is to run too lean. At one point I had the 1406 running in the 15-16 AFR range during cruise, and gas mileage did not get any better. I finally gave up on the Edelbrock and rebuilt a Quadrajet.

I am running about that same 13.5 AFR with my Quadrajet, and the engine runs better than it ever did with my Edelbrock 1406. The throttle response and drive-ability is much better with the Quadrajet, but I have not had time to recheck gas mileage.

Bruce

the suburban came with a 70's quadrajet, it needed a acc pump and when i soaked it in chem dip it seemed nothing worked, it wouldnt idle under 1000 rpm and ran like a dieing cat until it reached op-temp.

i decided that now i should see what was going on inside the qjet. stripped her apart, adjusted the float to just under 5/16 and after a few minutes of adjusting the mix screws its still idling lean >>15-16.5 afr but 2000-2500 rpm is 14.7>15 afr.

amazing...

i love quadrajets again =]
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  #23 (permalink)  
Old 06-24-2012, 08:52 PM
How fast is fast enough?
 
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Quote:
Originally Posted by LEROYDOZOIS
the suburban came with a 70's quadrajet, it needed a acc pump and when i soaked it in chem dip it seemed nothing worked, it wouldnt idle under 1000 rpm and ran like a dieing cat until it reached op-temp.

i decided that now i should see what was going on inside the qjet. stripped her apart, adjusted the float to just under 5/16 and after a few minutes of adjusting the mix screws its still idling lean >>15-16.5 afr but 2000-2500 rpm is 14.7>15 afr.

amazing...

i love quadrajets again =]
That 1406 would work fine if you didn't fubar the tune. Not saying qjets are bad carbs but the 1406 is about as easy as it gets.
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  #24 (permalink)  
Old 06-24-2012, 09:03 PM
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Quote:
Originally Posted by ap72
That 1406 would work fine if you didn't fubar the tune. Not saying qjets are bad carbs but the 1406 is about as easy as it gets.

so then what calibration would you have recommend me use for the 1406?
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  #25 (permalink)  
Old 06-25-2012, 04:41 AM
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Quote:
Originally Posted by LEROYDOZOIS
so then what calibration would you have recommend me use for the 1406?
Nothing wrong w/baselining the Eddy carb to factory specs for the next project, but I would leave the Q-jet in place and -if needed- fine tune it.

If you are having any other issues w/the Q-jet, we can help w/it as well. I believe the time spent working on carbs will be best spent working w/the Q-jet.
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  #26 (permalink)  
Old 06-25-2012, 07:09 AM
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Quote:
Originally Posted by LEROYDOZOIS
so then what calibration would you have recommend me use for the 1406?
I already told you, starting with what you have swap in the 7057 rods and a 6" spring. Also tune your idle feed for best vacuum not afr. Adjusting those two things would take all of 10 minutes and be a LOT closer than what you did.
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  #27 (permalink)  
Old 06-25-2012, 09:23 AM
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Quote:
Originally Posted by cobalt327
Nothing wrong w/baselining the Eddy carb to factory specs for the next project, but I would leave the Q-jet in place and -if needed- fine tune it.

If you are having any other issues w/the Q-jet, we can help w/it as well. I believe the time spent working on carbs will be best spent working w/the Q-jet.

the only issue im having with the qjet is its idling lean ~15.5>17

so last night i pulled it off and adjusted the float from a tad under 5/16 to 1/4 and im going to see if that helps. i guess some symptoms of ideling rough is float too low so i started there ( and i got all the internal specs out of the carb except the power piston spring so i needed to remove it anyway )

i took the mix screws out to 6.5 turns like what it was when i got the truck and at that setting the needles wiggle a little bit. i might put them back to 5.5 like how it was yesterday while it was running
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  #28 (permalink)  
Old 06-25-2012, 09:50 AM
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Quote:
Originally Posted by LEROYDOZOIS
the only issue im having with the qjet is its idling lean ~15.5>17

so last night i pulled it off and adjusted the float from a tad under 5/16 to 1/4 and im going to see if that helps. i guess some symptoms of ideling rough is float too low so i started there ( and i got all the internal specs out of the carb except the power piston spring so i needed to remove it anyway )

i took the mix screws out to 6.5 turns like what it was when i got the truck and at that setting the needles wiggle a little bit. i might put them back to 5.5 like how it was yesterday while it was running
What is the primary throttle shaft fit like? If it's worn too much, you will be pulling air in past the worn shaft bores and this can cause a poor idle. Be real sure there are no vacuum leaks. It doesn't take much to screw up the idle.

Also you might have real small idle mixture discharge ports. Opening them up to around 0.090" often helps, you'll also need less turns out so less chance it'll pull any vacuum around the idle mix screws. You can do this w/the carb assembled, just remove the idle mix screws and carefully drill the orifice at the end of the hole to 0.090" or so (don't go crazy- the screw still has to close the hole off). Clean the hole out w/carb spray and reinstall the screws.

If you still need a lot of turns on the idle screws, the idle tube channel could be full of junk at the bottom. This is hard to clean properly w/o removing the idle tubes.
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  #29 (permalink)  
Old 06-25-2012, 05:11 PM
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Quote:
Originally Posted by cobalt327
What is the primary throttle shaft fit like? If it's worn too much, you will be pulling air in past the worn shaft bores and this can cause a poor idle. Be real sure there are no vacuum leaks. It doesn't take much to screw up the idle.

Also you might have real small idle mixture discharge ports. Opening them up to around 0.090" often helps, you'll also need less turns out so less chance it'll pull any vacuum around the idle mix screws. You can do this w/the carb assembled, just remove the idle mix screws and carefully drill the orifice at the end of the hole to 0.090" or so (don't go crazy- the screw still has to close the hole off). Clean the hole out w/carb spray and reinstall the screws.

If you still need a lot of turns on the idle screws, the idle tube channel could be full of junk at the bottom. This is hard to clean properly w/o removing the idle tubes.
the shafts arent the greatest but theyre about as bad as the qjet on our 82 silverado and she purrs like a cat. ill do the drilling mod you just told me here in a few minutes, ill see what the deal is... ill get the numbered drill index out and see what the current ~dia is compared to the .090 reference you gave me
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  #30 (permalink)  
Old 06-25-2012, 06:57 PM
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okay,

so after drilling the needle seats to .093 and backing the needles out to 6.5 turns its sitting at 16.5 at leanest idle. obviously thats not the greatest but its better then before, im assuming as it shows in my quadrajet book that id have to drill the ventures out.

by chance could i flatten or cut the mixture screws down to make them richer at less turns ? just a thought =/
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