WEEPING/LEAKING 40 DCZ 6

My 330 has the standard 40DCZ 6s which have been rebuilt a year ago with new throttle shafts, throttle plates, jets, gaskets, floats were adjusted etc, etc, in short they were rebuilt from A-Z and have been functioning well all along. However, with the engine shut off, carb #2 is weeping/leaking fuel from the "left" throttle shaft only and is not leaking from the carb. top cover assembly or anywhere else. I have disconnected the fuel line and I can see it leak very slowly. It leaks with the carb. top cover assembly off. The fuel leaks through the left "exhaust valve # 18" and not the right one. Both of these "exhaust valves" are in the bottom of the bowl. It will leak until the fuel level in the bowl reaches a level below the side hole on the "exhaust valve" and by then the bowl is almost empty.

Thank you for any assistance in solving this irritating problem!

 

Thank you for your speedy responses. Yes, the bodies were bored to accept oversize throttle shafts and your thoughts make sense. The crack most likely developed due to shaft wear because of the oversize bore leaving little "meat". If that's the case, then there isn't much that can be done to rectify the problem. One option would be to put a sleeve in; the other, get an other DCZ. And yes, zinc does have a usable life. Sorry for the nomenclature but I used the exploded diagram for the DCZ and the available nomenclature from Pierce Manifold's site. I will take the unit off and follow through with your recommendations. I will keep you posted on the results.

 

The rebuild was done locally. I followed your recommendations, Brian and there was no apparent air leak. Maybe the fracture is so fine that no noticeable volume of air can escape but fuel can weep through that very same hairline fissures. I filled the bowl and fitted the top cover assembly (without the floats) and the carb. is going to sit overnight on the workbench. We'll see tomorrow. Thanks!

 

Thank you very much for your input, Brian. The leak was there this morning and I have been on a quest trying to find the recommended "Loctite 290". I figure, I may just as well give it a try, who knows? If it doesn't work, well there's always plan B (and C & D). I'll let you know how all this turns out.

 

Thank you for your input, Ed. The problem is simply that fuel in the bowl is seeping/weeping/leaking out the body even when the fuel line is diconnected and the carburetor is sitting on the workbench with the top cover assembly off and the floats removed. There is no fuel running down the throats at all which could possibly cause hydraulock. The carburetor body is in very good shape, no visible cracks/fissures, dings etc. All the working internals have been replaced and oversize shafts installed. So far, all indications seem to point that the problem is somewhere else - an internal or near surface fissure opening on a casting porosity near the accelerator pump assembly/well.

Brian, I followed your recommendations and the carburetor is on the car. So far (4hrs), there is no weeping and if it holds, I will fire up the engine later on today - and see.

 

Thanks Ed, I didn't try JB Weld because I didn't think it would work so close to fuel, although I have used it successfully to hold a couple studs that were holding down the air filter assembly. I really didn't want to go the Heli-coil way, so JB Weld saved the day. It's held up for 4-5 years now.

Brian, it didn't leak all day. I fired up the engine and exercised it a bit to get it very hot. Hopefully, that would work the zinc some and quite possibly make it weep again. So far, it is holding. I had three areas of concern. One was under the main jet where it joins the carburetor body, underneath the bowl, there was minute porosity. The second one was in the operating rod chanel - right into accelerator pump well; again more porosity. The third (hopefully last), in the throttle shaft passage there was a hairline fissure. I had to use a loupe to locate all those leaks. The Loctite 290 worked well and if it leaks again, I know what to do.

Thank you very much for your assistance, Brian. Thank you ALL.