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Sooty day’s...
#1
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Hmmmm.... Thoughts? Soot on my finger is from inside the tailpipe. Factory correct Rochester Quadrejet carb.... Way too much fuel entering the engine via the carb. Diagnosis time...
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#2
looking at the floor, i'd say u had condensation in the exh pipe and when u fired it up it shot out.. should not be a problem.. self cleaning.
do only drive short distance? this can build up soot, or is engine smoking this also will soot up.
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#3
(05-24-2019, 05:39 PM)Dear delawarebill Wrote: looking at the floor, i'd say u had condensation in the exh pipe and when u fired it up it shot out.. should not be a problem.. self cleaning.
do only drive short distance? this can build up soot, or is engine smoking this also will soot up.

Definitely some condensation for sure. My bad, the car is not run often and even less on the road. But, there is another issue for sure. After writing this I went out and looked at the carb. Both idle mixture screws were turned in all the way, seated. I noticed fuel coming out the top of the accelerator pump, puddling when the car is running. The exhaust is burning my eyes... You can smell the unburned fuel. I think I have a flooding issue. What pisses me off is I paid a guy to set the carb up over a year ago. Who sends a car out the door with both idle mixture screws Seated? The car always starts and runs, choke works; but I could always smelll unburned fuel and see the Smokey exhaust. May have to pulll the carb. And check the float and needle valve.
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#4
The low life you paid is at best a thief, and that is to insult to thieves worldwide. This may sound a bit off but, ask the local GM guys who is good at 60s-70s Rochesters. Personal experience references being the most valuable. Rochesters can be as problematic as 4300Ds but, there are know fixes for the GM stuff which applies to your carb as well. The biggest difference is the fuel inlet. I'd also change the oil and filter, excessive fuel contamination can do bad things to an engine. I hope you get it sorted out without too much drama and cost. Chuck
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#5
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So, I decided to take the carb off and check the float and needle seat set up as this would be the main reason for excessive fuel getting into the engine. I know the choke is working correctly, the car runs and wants to run.. I found out that the idle mix screws had been seated by the mechanic who I trusted to set the carb up... Shows you can’t trust anyone these day’s... At the end of the day, if you are going to own one of these classics, you have to learn to do the work yourself. I can do a lot, but the carb set up has always been a challenge for me personally. Well, that changes moving forward. I have yet to confirm the set timing, but decided to wait until I confirm the internal of the carb itself...

The second pic confirms this is the correct date coded carb for my car, based on my car’s build date. Pt. #7040286 is the correct part # for a ‘71 429cj with the C-6 trans and factory A/C. $1500 US $$$ paid for this piece (restored), simply because I wanted the date code correct piece... The date code on this carb is located just below the Pt. Number. It reads 3550. This equates to December 21, 1970, which is within general acceptable timelines for my car’s build date.

Now, I will take the top housing off to see what is happening here. Stay tuned.
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#6
For sure sounds like a float or float setting issue. The 4300 had a special float check gauge that could check the carburetor on the engine without removing from the vent hole.
I know nothing about a Rochester for sure. Be very cautious when you take the 4300 apart there are small ball bearing and also a needle seat that will fall out when you turn the carb over.
Do a google search there is a carb guy that has lots of informative video posted. Can't remember his name, lol.


When a man is in the woods and talks and no women are there is he still wrong??
Tongue
David
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#7
Do you have a manual for Quadrajets? Mike's Carburetor Parts has a lot of free manuals for download (including Quadrajet), as well as hard to find parts, like throttle shaft bushings, and other information.
https://www.carburetor-parts.com/Free-Ca...p_274.html



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#8
C
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Making progress... but maybe not. as you can see, the carb is spotless inside. I pulled the fuel inlet needle valve, perfect shape. Pulled the needle valve housing to bet a good look to ensure no obstructions, again, clear as a blue summer sky...

While I have the carb off, I confirmed that the plugs underneath were 2 part epoxied as this can cause a fuel leak. Also confirmed the metal shim is in place on the needle housing before screwing back into the body. Again, this looks good.

The float seems to sit ok, haven’t checked specs yet, but it seems okI will confirm the factory measurement before putting the carbback together. Time to do more research...
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#9
(05-25-2019, 12:44 PM)Yes Don. Haven’t looked at yet. This will be my next step, just wanted to check for the obvious first. I don’t want to put the carbback together until I have checked everything I can. The problem is still out there, I will keep at it. I am going to ask some GM guy’s for opinions also... ThxDon C Wrote: Do you have a manual for Quadrajets? Mike's Carburetor Parts has a lot of free manuals for download (including Quadrajet), as well as hard to find parts, like throttle shaft bushings, and other information.
https://www.carburetor-parts.com/Free-Ca...p_274.html


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#10
Hi Ken: looks like you dove right into the carb issue. Old school carb tuning technique I've used since the 60's as an initial setup. Once you have things re-assembled, initial tuning at warm idle would be to hook up your engine analyzer to monitor rpm and dwell and hook up vacuum gauge. 1 -1/2 turns out the on mixture screws. Using 1/8 - 1/4 turns on each mixture screw (let it run for 15-30 seconds before another adjustment) set it to the highest vacuum you can achieve.

Once you have set it as best you can using this technique, see if you can find someone who can plug emissions analyzer into exhaust pipe to check readings. Obviously the folks who do this on a dyno can do the best job since they can set it up with loaded conditions. Problem is finding someone who understands Q-jets with dyno.....
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