Got it installed and running

[GSP7]

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  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?


.

[lightning boy]

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.

[GSP7]

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

.

[GSP7]

....... 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


.

[quadrajam]

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

[Kenth]

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.

[GSP7]

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.

Cliff told me to set the float level at 9/32-10/32. Its set at that
( I know carb specs say 3/8"(12/32) and that is what I set at previous rebuild at years ago)

Is the Float level set wrong?

I can screw down the APT screw all the way and it runs fine ( Orange PP spring used Cliff recommended)


Quadrajam-
Yes the hanger arms were checked for level/straight before install

Vacuum at idle it 15-17 (motor has RV cam, cam lobe centers int.105, exh.115, lobe separation 110)

Yes the vacuum advance is working

[77cruiser]

A couple more degrees of timing might fix it.

[quadrajam]

Float level is good. I recomend 73 jets and switch to the dark blue PP spring which
starts to lift around 9 inchs vac. 3-1/2 turns up on the APT. Been there, tuned that.

QJ
 

[Kenth]

No increased rpm at "tip in test" with APT seated indicates a too rich mixture.

A too high float setting (too early delivery of fuel to the circuits makes a too rich mixture) and you may loose control of the APT adjustment.
Also too high fuel pressure will make the fuel level too high (same result, rich mixture).

No increased rpm with APT seated indicates a too rich mixture.

It is NOT a good idea to set the float at the same setting in different makes of the Quadrajet since the brass inserts in the center nozzle are different size in nearly every make, Buick, Cadillac, Chevy, Olds, and Pontiac all have their own nozzle sizes to start fuel delivery to the circuits depending on the demand from their engines.
Then you´ll have to calculate jetting depending on air bleed sizes.

As i said, ALL calibration starts with the float setting for the make of the carb that´s a candidate for a certain engine.

If correct float setting does not help, use a smaller main jet OR a larger primary rod to have the desired result.

"One size simply does not fit all, try walk a mile in your spouse's shoes."

[GSP7]

Im thinking the Float level is set too high also. The specs for this carb do specify 3/8" (12/32"), Not 9/32"

Kenth, sent you a PM

[GSP7]

Is this new base gasket going to be OK to re-seal if pull the carburetor back off to reset the float??

Its a 4x4 truck, gotta stand on a step stool and then lay across the radiator and front of the truck to work on the carb. PITA

[Cadman-iac]

Is this new base gasket going to be OK to re-seal if pull the carburetor back off to reset the float??

Its a 4x4 truck, gotta stand on a step stool and then lay across the radiator and front of the truck to work on the carb. PITA

 It's been my experience that if the gasket isn't too old or been crushed from over-tightening then it'll be fine. I've installed and removed my carburetor multiple times while tuning it.

 Rick