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81
Quadrajet Carb Talk and Tips / Re: Got it installed and running
« Last post by Kenth on March 04, 2025, 02:43:26 AM »
Quote from: GSP7 on March 03, 2025, 05:31:35 PM
Like I said above,,,,, I was able to turn the APT screw all the way down and it didnt cause any issues at all, not even and "buck and surge" at all. It drove the same with the screw down seated, cept for the hesitation... Im wondering what's the deal? Its a 3/4 ton truck carb if that matters #17080213.

All calibration is based on the float adjustment.
What is your float set at?
#17080213 should be at 3/8".
If higher the mixture gets richer, if lower the mixture gets leaner.

And the APT starts rising the power piston at 2 turns up from seated.
3.5 turns up from seated is in fact 1.5 threads lift.
82
Quadrajet Carb Talk and Tips / Re: Got it installed and running
« Last post by quadrajam on March 03, 2025, 06:51:27 PM »
Are you sure the centrifugal and vacuum advance working OK?  What is the vacuum at idle?
How bout the vacuum revved up a little like 1200 rpm or so?
Were the hanger arms straight and level?

QJ
83
Quadrajet Carb Talk and Tips / Re: Got it installed and running
« Last post by GSP7 on March 03, 2025, 05:31:35 PM »
Quote from: lightning boy on March 03, 2025, 01:24:21 PM
....... As far as the APT I trun the screw down until it starts to buck and surge from part throttle acceleration and then turn it out until that goes away plus a quarter turn. this will be the leanest you can run it.
........

Like I said above,,,,, I was able to turn the APT screw all the way down and it didnt cause any issues at all, not even and "buck and surge" at all. It drove the same with the screw down seated, cept for the hesitation... Im wondering what's the deal? Its a 3/4 ton truck carb if that matters #17080213


.
84
Quadrajet Carb Talk and Tips / Re: Got it installed and running
« Last post by GSP7 on March 03, 2025, 03:32:21 PM »
Got idle mix screws adjusted, set timing up to 10 degrees at idle with vacuum plugged, set idle about 500 + rpm

Messed with APT at 2000 rpm and closing the choke flap. Original setting was 3 1/2 up . It never went up in rpm and I ended up going all the way down with the APT screw. It still wouldn't increase in rpm closing the choke flap at 2000 rpm.

 Drove it around with APT completely screwed all the way seated down . Drove fine. But no matter what setting APT or timing there is a hesitation costing about 30 mph and the accelerating, there is a hesitation

The reset the APT to 2 1/2 turns up , just because. Drove it some more. Runs fine still, but there is still a hesitation when accelerating from costing about 25-35  mph and then accelerating, I get a hesitation before the truck accelerates


Not sure what is up with being able to turn the APT screw all the way down and seated and runs ok. ?
'
Its a 350cu.in. sm blk chevy, 1981 4x4 truck. 17080213 carb has new 72 jets and Cliff's 50ccustom rods. It Isnt the original carb that i removed which is a 17080513

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85
Quadrajet Carb Talk and Tips / Re: Got it installed and running
« Last post by lightning boy on March 03, 2025, 01:24:21 PM »
Congratulations! I would warm it up and run the mixture screws in until you can hear a lean roll from the exhaust at the back of the truck, then turn the screws out until you see the highest vacuum reading. Make sure there is no nozzle drip from the boosters. As far as the APT I trun the screw down until it starts to buck and surge from part throttle acceleration and then turn it out until that goes away plus a quarter turn. this will be the leanest you can run it.
I know you set the initial timing at 8* but I would see what the total timing is too. Good Luck.
86
Dialing in your rebuilt Quadrajet carburetor / Re: Tuning/ Dialing in my new rebuilt Q jet
« Last post by GSP7 on March 03, 2025, 08:49:49 AM »
Is the a inclusive written guide to dialing in a new rebuilt q jet on a 350 chevy sm blk?

Timing, idle mix screws, APT adjust, vacuum gauge use, etc etc ?
87
Dialing in your rebuilt Quadrajet carburetor / Tuning/ Dialing in my new rebuilt Q jet
« Last post by GSP7 on March 03, 2025, 07:43:13 AM »
I do not see any where in Cliffs book on dialing in tuning my new rebuilt carb

I thought there was a APT adjustment section , but I dont see anything about adjusting the APT  , etc etc

Any help

Ive got a newly rebuilt 17080213 installed replacing my old 17080513 on my '81 chevy K20 4x4 truck with mildly built 350

Need info on dialing the carb in.   I guessed on the APT setting at 3 1/2 turns up . Original APT Setting was way wrong on this core carb I got off ebay that I rebuilt

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88
Quadrajet Carb Talk and Tips / Got it installed and running
« Last post by GSP7 on March 01, 2025, 02:09:29 PM »
Weather warmed up and snow is melting. So I got my old worn 17080513 pulled off my '81 350 sm blk, K20 chevy truck. Spent several days cleaning up the intake manifold and then masked it off an fresh painted it chevy 1620 orange.

 This morning unmasked every thing and reassembled that I took off, and got the new replacement, rebuilt with Cliffs parts, 17080213 carb installed on the chevy 350 and running. Checked for leaking fuel at the filter fittings, none.  Adjusted the new electric choke conversion as it got warmed up, fiddled with the idle mixture screws alittle and then back to two turns out. Slowed the idle down.

Warmed up, choke off, I throttled up to 2000 and slowly closed the choke flap, no increase in RPM... ok for now, it seems. Had a wet towel and fire extinguisher handy  ;D didnt need it so far

Took the truck for little spin down the hill and back to my house ran pretty good . Maybe a tiny hesitation at after first taking off(mid throttle). Accelerator pump and response from dead stop was crisp.

Eating lunch.... Ill pull it back in the shop check 4 bolts and air horn screw tightness from first warm up and cool down.

I put in new #72 jets and Cliffs Custom 50m rods.

APT I set at 3 1/2 turns up for starters. I used the Orange power piston spring recommended by Cliff

The new Idle mixture screws I installed at 2 turns out, to start with.

Tomorrow I play with it more trying to tune the APT etc.

The distributor timing was set at a safe, 8 degrees advance at idle, with vacuum advance plugged with the other carb.

Any tips on getting the carb dialed in?


.



89
Diagnose a Quadrajet carburetor problem / Re: Not sure what my Carb problems are
« Last post by Cliff Ruggles on February 28, 2025, 04:20:23 AM »
1975 passenger car carburetor with the APT adjustment under the brass cup the left front of the airhorn (as viewed from the front).

Those aren't that great as mentioned in my book and their existence was very short lived.  I had so many problems with them in the shop back when we were doing rebuilds and restorations I quit taking them in. 

Not saying you can't make it work, but I've ran into just enough of those that don't work well no matter what you do to them to avoid them completely.  Rochester knew there were flaws in the design and very quickly discontinued them in 1976 and went to the far superior late style units with the APT screw in front of the power piston that raised/lowered tapered metering rods for fine control of the primary side A/F.

Your symptoms indicate going WAY lean right off idle, which could be many things, but I'd start by putting one of my rebuild kits in the carburetor as the accl pump in the kit you bought isn't worth two squirts of duck poop, plus the N/S assembly is incorrect with a pretty small hole in it which effects the fuel level in the bowl and overall metering to the engine.  Also verify that the PP hanger arms are level and EXACTLY even, which seldom happens with these things.

You also mentioned "adding an electric choke".  Did you do the conversion correctly by blocking the vacuum BEFORE the choke housing or using a later choke housing designed for an electric choke. 

I see a LOT of carburetors that have had electric chokes added to them, and maybe one it fifty was done correctly......FWIW.....
90
Quadrajet Carb Talk and Tips / Re: wings on my base gasket
« Last post by quadrajam on February 24, 2025, 11:22:35 AM »
I tried to tell Cliff those winged gaskets werent gonna go over very well........

Guero, pick up the phenolic spacer and turn the gasket around and set
the spacer straight back down. Then  post another picture of it.

If all else fails use a 4 hole gasket.

QJ
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