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Discussion Starter #1
Took a stab at rebuilding the Q-Jet the PO installed. The cleanup and reassembly was easy, tuning turned out kinda bad. On first start up the motor was running real rich. So I popped the top off, reset the float, and buttoned it back up. Second start up was much better, but still rich. about 30 seconds after it was idling, it started knocking, LOUD! Turned it off, and check to make sure all the carb screws were in place; CHECK,, all good. Nothing went down the carb. Started it back up, still loud. Pulled off each plug wire one at a time to try and isolate the sound. No luck. One did change it some, but not much. Got pissed. Let it sit for an hour, started it back up, reved the piss out it, it got a bit better. Hmmm. Let it sit over night, and this AM it is still knocking but not as loud. Any ideas? MY guess is the carb dumped so much gas down the cylinders it washed off the oil and it messed up a rod or six.
 

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Long term extremely rich running can wear cylinder walls; you aren't going to damage an engine in a few minutes, hours or days.

Float level is really only to keep an ideal amount of fuel in the bowl; you don't tune mixture with float level.

Assuming you are running on the idle circuit (It's possible to get it so wrong that you end up running on the mains) the only way to adjust idle mixture is with the idle mixture needles (screw).

Knocking is usually big deal; that the engine has been running, presumably for 30 years, and starts it's death rattle right when you are working around the intake is a little suspicious. You might want to revisit your "foreign object" idea. Otherwise check and smell (for LOTS of fuel, not a hint) the oil - does the oil pressure gauge work?
 

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Discussion Starter #3
I hear ya on the suspicious. Look for a valve not opening all the way?
 

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i'd pull the valve covers. has it backfired or pinged lately? mine started knocking after some pinging, pulled the covers and found a rocker nut backing off. luckily no bent rods.
 

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Discussion Starter #6
I too thought about the timing on the way home from work!! Had t-ball games all night, kids in bed, I'll get the gun on it tomorrow evening.
 

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Discussion Starter #7 (Edited)
OK, update. Timing with Vac Adv removed, about 8 deg advanced. Timing with VA on, off the chart advanced. May have an issue here, but I'm a rookie on these old dizzies as they call em on here! Tried both vac ports on Q-jet same reading; way advanced. When I pull the vac line off the carb and plug the carb, then it stays at the base reading. When I give it some throttle, it advances slowly.

Oil flowing like a chocolate waterfall off the rocker arms on Passenger side, and all moving same amount, no bent push rods. Off to look at the drivers side. BTW, heads look real clean no gunk at all. I did find a small leaf fragment semi blocking the oil return hole on the front of the head.

Driver side same as passenger side; good oil flow, all looks normal. I'm just guessing but I think it's deeper. Oddly, it's not as bad today, but gets a tad louder as the motor warms up. Oil pressure is just a tad below the middle of L and H. Oil looks like it need to be replaced.

Buttoned it back up and took it for a test drive. Knock got got louder as I went faster. Then Knock went away. LOL, holy crap!! I guess the starter could have been hitting the fly wheel, but I've heard that before and this was not it. Goofy. Time will tell.

Going for new plugs and wires and working it from there.



Fumes bad, think i have carb / ignition issues.

KJ
 

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If you are getting gas fumes then you probably need to adjust your mixture screws like it was mentioned before. Adjust your idle mixture, idle, and then maybe check the timing again after that to make sure. My Q-jet is a little hard to get tuned perfectly, but once it is it runs amazing. It is definately a lot of trial and error until you get it right. Hope this helps.
 

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Discussion Starter #9
I think the power valve is not responding to vacuum, that is, it's staying wide open. Or, the secondary needles are not fully seated. Or it's just an old POS. I'm gonna run threw it one more time this weekend, armed with some documentation on how to tune these things and gauge.

Found this site the other day, lots of info: http://www.florida4x4.com/tech/quadrajet/
 

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Discussion Starter #10
Well, this thread is old, but I thought I'd update it anyway. Found a Holley 600 that was brand new for $125. No more carb issues. Tuned the idle settings with a vacuum gauge. The knocking is just a tick now. The motor will blow blue smoke when revved over 3000 RPM during hard acceleration. No visible smoke unless revved hard while in gear. Replaced: CAP, rotor, wires, plugs, ignition module, and voltage reg. Still runs the same. I think she needs new rings and a valve job. So do I for that matter!!! LOL!!
 
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