For a long time now, "remanufactured" carbs have been junk. See
here.
Nothing runs as well as a
new carburetor—a real one, new old stock, not the Chinese "100% new!" knockoff junk, and not the Argentinian "looks almost kinda like a Holley 1920 except it's pretty much not" units. Every day it gets harder to find a really good carburetor for these cars. I used to have a whole wall shelf full of 'em; almost all of them are sold and gone, though I still have the odd one or two including a primo unit for the '60-'65 cars with rod-operated throttle (won't fit your car). Maybe I should have sat on all of them; prices have gone up in accord with scarcity!
Two kinds of carb were factory equipment on Slant-6s in the 1962-'73 year range: the Holley 1920 and the Carter BBS. Which one any particular car wound up with was a matter not only of specification but also of what was at hand when it came time to install a carb on an engine at an assembly plant. The Carter BBS has some fairly large design and engineering advantages over the (especially 1964-up) Holley 1920, so if you were facing a choice between a brand new 1920 and a brand new BBS, the BBS would be the one to pick. These days, primo carbs are scarce enough that condition is more important than brand—that is, if the choice were new 1920 vs used/rebuilt BBS, the 1920 would probably be the winning bet.
If you can afford it, go pounce on
this carb (has a "make offer" option; try and see if they'll knock $100 off). It's one of the best BBSs, with all the improvements (gradient power valve, bypass idle air metering, hot idle compensator, etc) and a big truck-spec venturi. It will drop directly onto your '68; the air cleaner will drop on, the throttle and kickdown linkage will hook right up, the distributor vacuum advance and PCV hoses will go right on. The new carb's bowl vent hose is meant for use with the system described
here, which your '68 doesn't have; no matter, just leave that hose open to the atmosphere and you've got practically the same bowl vent arrangement as a '68 carb. The new carb will also have one additional small vacuum nipple meant for use with the '70-up thermostatic air cleaner; put a cap on it. The only other adaptation necessary is that the BBS has a front fuel inlet, vs. the 1920's side fuel inlet. You can either make a new filter-to-carb line out of a short piece of 5/16" brake line tubing, or take the excuse to do the
Fuel line mod and do yourself a favor.
If the previous owner was a hamfisted klutz, it's likely he boogered up the choke thermostat and pushrod; these are frequently found bent and twisted all out of line. Grab a № 1231
Electric choke kit, drop on and hook up.
The BBS in as-received condition will tolerate today's E10 gasohol (10% ethanol) fine.
Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted
here for free download.
Tune-up parts and technique suggestions in
this thread.
