Just putting the finishing touches on my 216 valve job. Rebuilt the distributor, radiators back from radiator shop, new oil feed lines to the rockers, in short, everything else I could unbolt from the short block has been redone. The last item on the list is my GM model “B”, pn.7002050, Rochester carb. Before I shut her down because of a burnt valve, I noticed that the idle screw had no affect on the way the engine ran. I could screw it in all the way and it still idled just fine and on the road it ran amazingly well. So I tore into it yesterday to find out what was going on, also just to make sure everything else was ok. Well it twasn’t!!!

The shotglass full of very fine “rust dust” wasn’t too much of a surprise since the only filter was the wire screen in the fuel pump which by the way was also loaded with residue. Inside there were a few things that didn’t match up with the manuals and I would like to hear from you carburetor experts out there.

The first thing I notice right off the bat was a rattle in one of the floats or should I say a splash when I shook it. Yep, a tiny leak, in the center of the bead, on the inside of one of the floats. I’m sure that I can drain it and solder the hole shut but haven’t figured out how to leak check it yet. Ideas???

The second thing doesn’t need explaining but again it surprised me that the engine ran so well. The power piston was stuck solid. I didn’t want to take a chance of bending it so I made a little soft-clamp that I put in the drill press so I would have a straight pull on it. It finally let loose after soaking with some Kroil. Also the spring is stuck in the piston and I don’t want to stretch it out trying to pull it out, as this could change the response of the power piston. Normally I should be able to remove it unless this is something that is different on these carbs. Anyone ran into this??

The third thing was, the screen and retainer in the base of the accelerator pump well was missing. I’m guessing that it might have been left out during a previous rebuild. So I suppose it needs to be replaced. I was going to cut a new one from some fine brass cloth and make a retainer from a coil cut from a tension spring. Anyone found this missing from their carb during rebuild?

The forth item is a little trickier to describe. It’s the “pump discharge spring stop”. In the past all of the carbs that I have rebuilt only used the T’ shaped spring stop that was pressed into the hole and this kit has a new one like I expected.
However, on this carb there is a something called a “pump discharge guide”. This looks like a round plug with a slot cut about 80% of the way through one side and apparently is inserted into the hole and then the slot is expanded. According to the GM “B” manual you should, “rotate it with a thin blade screwdriver until it is free and is pushed up by spring pressure”. No way can I get this to rotate so far. This well is most likely to be full of sediment and I really need to get this plug out to clear it. Any experience with this one?
I’ll stop here and see what ya all got to say this morning.
Denny Graham
Sandwich, IL

Note about old Carb Cleaners: I dipped the air horn and all of the small parts in a gallon of new/fresh Gunk Carb cleaner from Farm and Fleet, worked fine. Out of curiosity I soaked the throttle body and bowl in my 20-year-old gallon of Gunk Carb cleaner and it still stripped everything just fine. Long ago it had eaten through the original can, then every few years it would eat thorough the plastic jugs but the HDPE jug its in now seems to be holding it OK.

Denny G
Sandwich, IL