Reese Jacobs

The carb on my 1985 Delta was leaking a little bit of fuel on the intake so I figured while it was parked for the winter I would treat the 35 year old piece to a "rebuild" and simultaneously learn something about it. Few things:

Ordered a proper kit online with new o-ring type secondary well plugs and unfortunately based on the teardown this morning, it looks as though its the primary well plugs leaking. Is fuel-resistant JB weld the only fix on the primaries?



I also come across this ecm connector and the power piston. I see that this top screw is an adjustment to that top plate and I dont want to fiddle with that. Im not sure where to proceed as I want to clean up the passages and such but dont want this to domino into more than I intended. Carb ran good before this, just maybe some leaky gaskets. Can I get away with just a quick spray down on this area and focus more on the other surrounding passageways ?


Ultimately this a big learning experience for me, I just dont want my curiosity to blow up in my face. Advice appreciated!

joe_padavano

First, that is probably not a fuel leak. That cavity is open to the intake plenum. What you are seeing is almost certainly deposits from reversion flow in the intake. If you really subscribe to the "leaking well plug" myth, then before you hack at those plugs, prop the fuel bowl up over a piece of white paper and fill the bowl with gasoline or alcohol. Let it sit overnight. If there's no evidence of wetness or leaking under the plugs, there's no leak. The well plugs will not cause a leak on the intake, it would be inside the intake.

Second, the CCC Qjet requires a very finicky adjustment process. Get a factory Chassis Service Manual and read the section on carb rebuilding. If you don't follow the process EXACTLY, you'll make it worse than it was before.

Third, always replace the float when you have the carb apart like this. It's cheap insurance against ethanol-caused deterioration of the plastic.

Fourth, there are some specific tools and gauges needed to adjust this carb. You can work around the gauges by making surrogates (dimensions are in the CSM), but the "double D" wrenches are really hard to do without.

Schurkey

Yep. You NEED the Genuine GM service manual. These carbs aren't "difficult" to rebuild, but they are tricky and particular about getting the adjustments right.

Have the idle mixture "tamper-proof" covers been removed yet?

Make sure the mixture-control solenoid works. They used to be a high-failure item. Perhaps they've been improved since '84, when I was in a dealership. O2 sensors get lazy with time and mileage; they react slowly, and can even give "false" readings. You almost certainly need a new O2 sensor at carb-overhaul time.

Do you have the idle-control motor that hangs off the side of the carb? Some applications got them, some didn't.

As with almost any GM "computer-controlled" engine, a real scan tool is VERY recommended. Ideally, you verify O2 sensor readings, Mixture-control solenoid operation, and make sure the other sensors, ignition timing, EGR, spark plugs and wires, etc. are all working correctly before removing the carb. That way, you don't blame the carb for problems elsewhere in the system.