Carburetor Out

Took the carburetor out Saturday night. It was a pretty straight forward affair. All the nuts broke easy, and only one was hard to get at, being tucked in a recess behind the float bowl. Once I got it off, I was able to get a closer look at the body, to try and find ID markings and such. Rochester carburetors from that era came from the factory with a triangular tag under one of the float bowl screws. If that tag is gone (which ours is,) you basically have to go get access to GM's blueprints to figure out exactly what model you've got. This pic of a nicely restored '57 shows exactly what we're missing:


I did find a casting number on the base plate that read "GM195812," and I'd say it's a pretty safe bet that means it was made in 1958. That adds to my conviction that the engine we've got came out of a 1958 Chevy. The stamped number on the engine block reads "F0605D," and that D-suffix means it's a 283 from either a 1958 or a 1960. We might need to invest in a 1958 engine manual, since there are definitely some differences from what's described in the '57 literature, though mostly minor.

I've been reading up on the operation of these carbs, and I think one of the big contributions to our engine issues (tons of smoke, rough running, some knocking) is that the tube that connects the automatic choke contraption to the exhaust manifold is missing, and looks like it's been missing for a while. Without it, the thermostat coil in the choke doesn't heat up, so the choke valve doesn't open as intended. Basically we've been running at full choke, cold or not, which would explain why it acts like the mixture is rich. :)

Today I cleaned up the interface on the intake manifold, scraped off the old gasket, etc. Part of it still has a nice machined finish, but a section in the front is pitted out. The two front studs are also corroded & missing some threads at the bottom. Those will require some care. There was also a little damper/dashpot/god-knows-what attached to front left stud that looks like it was intended to be a part of the linkage system, but definitely wasn't doing anything useful recently. That thing was one of the reasons for the missing threads. Here's a pic of it, any speculation as to what it's for is welcome:

From Exhaust, Carb Out, & Wheel Checkout