Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Another wet airhorn gasket thread...
Cliff Ruggles:
Also included in the rebuild kit will be a secondary cam/spring which need replaced during a complete/correct rebuild. Your kit will also come with a new filter/spring, and a new float. The small parts kit contains a new retainer for the power piston (split collar) so it slides right on w/o much effort.
The gaskets are the highest quality out there. Those cheap POS black "non-stick" gaskets showing up in other kits are the worst parts ever sold for these carburetors. I'll bet the Chinese are laughing their arses off selling us that part as they stick so hard to the main body and baseplate it takes about an hour with a razor blade to get them removed!
Rebuild kits can be found here:
https://cliffshighperformance.com/product-category/quadrajet-rebuild-kits
If you are not sure what you need or need to add items to a rebuild kit call the shop. I stock every part currently available for the Quadrajet carburetor and over 30 parts that have been discontinued and NLA elsewhere.
Anyhow, thanks for listening, back to the shop.......working weekends as I'm pretty busy this time of year........Cliff
lightning boy:
You test the needle and seat through the fuel inlet on the carb as per Cliff's book.
nUcLeArEnVoY:
--- Quote from: lightning boy on March 29, 2021, 01:34:52 PM ---You test the needle and seat through the fuel inlet on the carb as per Cliff's book.
--- End quote ---
I tested the SEAT seal, yes. As in the metal ring gasket. The test where you fill the bowl with soapy water and inject compressed air into the fuel inlet while applying firm pressure on the needle and checking for bubbles at the seat gasket. Checked out fine.
As for testing the needle and seat, I vacuum tested them OUTSIDE the carb by slipping a vacuum line over the entire seat, inserting the needle and applying vac to see if it holds. It wouldn't hold at low suction, but if I pumped it up to 20" or more, it held fine. Not sure about the conclusivity of that test?
What's his procedure for testing the needle and seat through the fuel inlet?
I did remove the fuel inlet and threaded in a vacuum fitting and tried applying vacuum while the needle was in the seat... wouldn't hold vacuum, but neither did the other three needle and seats I have. Hard to believe all three were bad, so I assumed that it was normal, unless I'm doing the test incorrectly, so definitely please let me know. ;D
FWIW, unless the soaked airhorn gasket qualifies as a flooding symptom, I'm not getting any signs of flooding. Car will idle all day, no nozzle drip, no overflowing, no issues with hot starts, no black rich exhaust, or anything indicating true flooding. Just the wet airhorn gasket, and it's seeming the consensus is a combination of airhorn warpage and the material my gaskets are made out of.
At the end of this month, I've decided to send Cliff my airhorn so he can flatten the front of it a bit. I don't trust myself to do it. Hopefully that'll help with the problem.
lightning boy:
Install a barbed hose fitting into the fuel inlet. (where the gas line threads into). Put a hand vac on the hose fitting, install the N&S assm and see if it will hold a vacuum.
It's common for the casting to be corroded below the flat metal washer. I worked forever trying to fix one before!
bry593:
I found that applying vacuum on the fuel inlet was not a positive way to evaluate seat leaks. Instead, dial your air compressor down and verify the pressure using the same gauge you used to measure fuel pressure (9 psi). Assemble your needle and float and add gasoline to the bowl. With your low float setting, you should see the bubbles stop when the float rises to about 3/8 from the top of the casting (in my case, this was slightly above the top of the seat). If bubbles don't cease, peen your seat and try again.
At any rate, if you are not having hot start issues or engine trying to die at a stop light, your float system is probably working just fine.
Another indicator of faulty seat is finding gasoline (wet) inside the hose to the choke pull-off diaphragm.
Most likely, you probably have just a spongy gasket as Cliff mentioned.
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