I had to pass this one on. Took in a carb yesterday that was having difficult cold start issues.
The owner said that otherwise it ran and drove fine.
He was having trouble after sitting for more than 24 hours and it took many cycles of cranking to get it to fire up. He had just had the carburetor professionally "rebuilt" by a carburetor shop/business in his area. He was certain the bottom plugs were leaking out all the fuel overnight causing the cold start issues.
I told him that he wouldn't like my findings as I knew the bottom plugs were not the issue. I've seen very few of these carbs leak (1980 Pontiac carb) but told him I would check things out and give him a full report.
So I removed the airhorn and internals. As expected it had the WRONG N/S assembly with a tiny little hole in it, one hanger arm on the power piston bent up, the other slightly down (no surprise there either), correct jets and metering rods, float looked fine, level was OK, etc.
Then the big surprise, the accl pump had an older "black" seal on it, which was still OK but the short time it had been in this new fuel it was swelled up slightly and very rubbery. Then I noticed that the accl pump had no spring or retainer on it. Well eureka we have found the problem, no accl pump shot, but keep in mind I was told that the carb worked fine other than the cold start issue.
I took a peep in into the filter housing to see if they had installed the later filter with a check valve and saw brass instead. I removed the filter housing and the filter was installed BACKWARDS!.........lovely.
So I attempted to remove the baseplate from the main casting and it's not budging. Another "skinned" black gasket found a victim so I had to beat them apart with a plastic mallet!.
Those cheap "skinned" black gaskets are JUNK and dubbed "non-stick". I'll bet the Chinese are laughing the arses off with that one. Anyhow it just adds another 30 minutes or so to the labor end of the job removing all that material with a razor blade.
I checked the baseplate and the primary throttle shaft was pretty "loose" and it needed bushings.
As expected pressure testing the main casting with 140psi compressed air showed that the bottom plugs were fine.
No other problems noted anyplace, but for sure there is NO WAY this carb was working well other than just a cold start issue. I suspect it will work a LOT better with some pump shot after the owner gets it back in place. It will probably work better at WOT too not that more fuel can enter the carb and it's getting filtered. It will also have more even distribution of fuel to both sides of the engine with the metering rods correctly located in the jets at cruise.
So there you have it folks, just a few things missed during the rebuild that made the owner think he had leaking bottom plugs, which by the way is a pretty rare occurrence in later model Quadrajets........FWIW......Cliff
