. . Recently acquired a '65 Impala Convertible. . Carb loads up bad and can hardly keep it running much less drive it. . Guy I bought it from said he put a kit in it but didn't make any difference. . I never take someone's word as 100% gospel and always want to know what caused the problem not just replace parts. .
. . I suspected a leaky float. . My friend said needle and seat. . We were both wrong, , Kinda Sorta. . Turns out the float topped out before it could close the needle. .
. . So the question is what would be a good ball park measurement for the float measuring up to the gasket? ?
Depends upon the make and model. Are we talking about a Carter AFB made and sold by Edelbrock. A Holley 4150 or a Holley 4160 (or a 4165 series and 4500 as far as that goes as they are all set the same) it is just open the sight plug and turn the adjustment screw until fuel appears at the threads to the sight plug on the side of the fuel bowl. If you have a Rochester there are a number of different models used and eacxh one has a different float level set with a ruler.
The 4GC was the most hated of all carbs by mechanics. Hard to tune even with a primitive analog gas analyzer (tail pipe sniffer), and it wouldn't stay tuned. for long. It was a poor performing carburetor that was quickly replaced by a Carter AFB or AVS by car owners which is why you have one now.
I beg to differ. The 4GC is one of the most reliable 4 barrel carbs ever designed. I rebuilt one for a friend and he ran it on his car for 13 years and a lot of miles with NO problems what-so-ever. I've rebuilt a lot of others that have performed great for years as well. They're as good or better than an AFB, but of course, they don't produce as much power.