Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Bad Leak from Baseplate Gasket
rwberinger4x4:
Hey All,
I recently purchased a new (rebuilt) quadrajet from a reputable builder for my 283 with Edelbrock SP2P manifold. This Quadrajet, Serial# 17058222 bolted right up and ran great for about the last 100 miles, but this weekend, the truck it's installed in would barely hold an idle, stumbling badly down around 450RPM, instead of the 700ish I had it set to.
Covering the air inlet in the top of the carb smoothed out the idle immediately, so I knew I was looking for a vacuum leak. Investigating with Carb Cleaner showed a big change in idle when spraying around the base gasket, where the carb meets the intake manifold. The gasket used was supplied with the carburetor by the rebuilder. It's one of the 1/4" thick, open-plenum gaskets with nylon reinforcing rings around the bolt holes.
The throttle shafts on this carb should already be bushed, from the rebuilder, so I don't think thats the issue.
Could the throttle plate have warped this quickly? I was careful to only torque the bolts to 12-15 ft. lbs. and it doesn't seem like they've come loose. Are manifold gasket failures common? Could I have just gotten unlucky?
A question for Cliff: I had ordered a rebuild kit for my old Buick Qjet I was trying to revive previously. You provided both a thick "open plenum" gasket as well as a thin, 4-hole gasket. I'm sure there was a method behind your madness, and I never had that setup leak at the manifold. Should I be running a similar 4-hole gasket with this new carb (ID 17058222)?
429bbf:
this may be a dumb question . did you match the gasket to the carb and intake before you installed it?ive seen where the gasket doesn't hardly seal on the carb on various setups .it seals for a little while and then sucks a vacuum trail past the gasket. fwiw
Cliff Ruggles:
Some Edelbrock manifolds will leak at the front with certain q-jet carb to intake gaskets. They will NOT work with the thick-open gasket with the cut-out in the front, you must use the solid version of that gasket...we sell them here.....Cliff
rwberinger4x4:
--- Quote from: 429bbf on April 19, 2016, 08:50:10 PM ---this may be a dumb question . did you match the gasket to the carb and intake before you installed it?ive seen where the gasket doesn't hardly seal on the carb on various setups .it seals for a little while and then sucks a vacuum trail past the gasket. fwiw
--- End quote ---
To be honest, I'm not entirely sure. I actually purchased this particular quad from Sean Murphy Inductions. Sean provided the base gasket with the carb he sent. He asked all the pertinent questions (what type of intake, etc.) before sending it so I made the assumption he sent me the correct gasket. However, looking at Cliff's response, he got me thinking...I'll follow up more after I quote him...
rwberinger4x4:
--- Quote from: Cliff Ruggles on April 20, 2016, 02:09:10 AM ---Some Edelbrock manifolds will leak at the front with certain q-jet carb to intake gaskets. They will NOT work with the thick-open gasket with the cut-out in the front, you must use the solid version of that gasket...we sell them here.....Cliff
--- End quote ---
Cliff, I think you may be on to something. I guess my question is - why? I'll try to upload some picture of my manifold and carburetor. Seems like there is plenty of meat up front on the Edelbrock to create a seal. The other thing that is weird is that it DID seal (for about 100 miles). I loosened up the carb bolts yesterday and re-tightened them, and it seal back up again...
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