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Diagnose a Quadrajet carburetor problem / Re: Choke pull off
« Last post by Cliff Ruggles on July 02, 2020, 04:39:37 AM »
The plastic pull-offs sold here are adjustable thru the inlet.  All the ones being sold currently are instant opening.  I modify each one so they can be adjusted per application......
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Diagnose a Quadrajet carburetor problem / Re: Choke pull off
« Last post by dlphil10 on June 30, 2020, 05:33:19 PM »
I ordered another pull off and got it to 2.25 seconds. This combined with 3/4 turn on the air valve spring provides the best results.

I have 2 targets now. A very slight off idle stumble that I've helped by using stiffer power piston springs. I'm trying to locate a stiffer spring that starts to lift at 12inHg, or maybe 13inHg. I figured that would imitate the APT system with later model carbs.

The second is my main concern. It's a few faint pulses in the exhaust at 1800rpm after going WOT from a stop. It happens a little while after going WOT, but then it clears right up at 2000rpm and is smooth until 5200rpm. Could I need larger jets (currently using 72s)?

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Good advice Cliff, I will do that.

I haven't checked the timing in a while.  Its probably time I do.  Won't be back out to the old girl for a few weeks but I will look at the timing next time.
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I would purchase a piece of stainless steel 5/16" threaded rod and make studs for the carb.  That is what I do here in lieu of using bolts as it ensures maximum thread engagement in the intake manifold.....
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you should have to bearly touch the key and it should catch on hot start,no touching the gas pedal. might need some more initial timing. i've always set initial by getting the motor hot soaked, advance 2*,shutdown, wait for temp to spike (~5 minutes) and then try cranking. if it starts good repeat the process until it hard starts/windmills then back of timing 2*.
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Got a chance to install and run the Carb this past week.  All I can say is Wow!

Two pumps of the throttle and one click of the key and she started right up and idled perfect.  Didn't really have to make any adjustments.  I got out past the no wake zone and hit the throttle to the floor and absolutely no hesitation, she jumped up and ran hard until I reached max RPM.  I had the idle screws set at 2.5 turns and thought about playing with that setting but after it warmed up it seemed so perfect I didn't touch it.  Idled at about 850 in gear, which is correct and about 700 out of gear.  I didn't touch it. 

Two things-

After running for a while and shutting down it took some cranking to get it started again.  It could be just a learning curve on my part.  I tried just turning the key, but maybe I need a couple squirts or to hold the throttle open while cranking.  That didn't happen every time either, several times after sitting for only a few minutes it started right up with just a turn of the key.  So again, maybe just a learning curve on my part.

The new bottom gasket is so thick the two front bolts barely caught threads.  I removed the washers in order to get them set but I will definitely need to get some longer bolts. 

Super happy with the rebuilt Cliff, thank you for the kit, the book and the advice in here.
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Quadrajet Carb Talk and Tips / 1986 GMC P/U with ESC
« Last post by tayto on June 28, 2020, 09:36:00 PM »
My 1986 GMC 1/2 ton Pickup has electronic spark control, basically just knock detection and it can retard the timing. It has currently been bypassed, but wondering if it is worth repairing. I will be swapping in my 355 over the next month. The internet says to get rid of it, but i don't see any harm in pulling timing if knock is detected. Thoughts?
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Quadrajet Carb Talk and Tips / Re: Upper Idle Air Bleeds
« Last post by jagness on June 26, 2020, 09:00:46 PM »
Installed brass inserts in the IABs, drilled to .048. Getting there!
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Quadrajet Carb Talk and Tips / Re: E10/15 fuel and vapor lock.
« Last post by blazer74 on June 25, 2020, 09:24:19 PM »
^Ditto^.
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